City of Grande Prairie - Stormwater Master Plan 2018 by City of Grande Prairie

City of Grande Prairie

Storm Drainage Master Plan 2018

Final Report (Revision 1)

Prepared for: The City of Grande Prairie Prepared by: Sameng Inc. Project No.: 1306 Interim: June 15, 2018 Final: August 27, 2018 Final (Rev.1): December 12, 2018

201, 17205 106A Avenue NW, Edmonton, AB T5S 1M7 (780) 482-2557 services@sameng.com www.sameng.com

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Executive Summary PROJECT BACKGROUND AND OBJECTIVES Sameng was retained by the City of Grande Prairie in November 2017 to undertake an update to its Storm Drainage Master Plan. Since the last master plan in 2012-13, the City of Grande Prairie annexed 6,316 ha of land from the County of Grande Prairie No.1; the City now covers an area of 13,658 ha. The City population also grew by an estimated 34% in the last decade. An updated drainage plan is needed to support this growth and the annexed land. The main objectives of this Master Plan are to provide a comprehensive review of the City’s existing drainage design standards, a review of rainfall and flow monitoring data, a thorough inventory of the City’s drainage system, the development of a comprehensive computer model of the drainage system, examine issues with the existing drainage system and identify upgrades to mitigate these issues, and develop an effective long-term drainage plan to allow future development to proceed.

REVIEW OF MUNICIPAL DEVELOPMENT STANDARDS The current City of Grande Prairie servicing standards are mostly in conformance with Provincial guidelines for stormwater drainage design, as well as other Alberta municipalities. Some recommendations to those standards were made. Of note, it is recommended that the stormwater management facilities sections be more descriptive and that standards for inflow/outflow structures and control devices be added. Furthermore, it is recommended that the design standards include a section that specifically discusses design criterion of water quality control facilities. One of the most significant recommendation is the update of the City’s IDF curves and design rainfall events. The newly developed IDF curves generally have larger intensities (10 to 60% more) than the current IDF curves for the smaller durations (less than 2 hours). For durations larger than 2 hours, the new IDF curves are similar to the current curves. Furthermore, it is recommended that the City update their design rainfalls for purposes of evaluating and designing storm drainage systems. They are the 4-hour and 24-hour Chicago distribution, and the 12-hour and 24-hour Huff distribution.

EXISTING DRAINAGE SYSTEM INVENTORY A thorough review and inventory of the existing drainage system was completed. It consists of storm sewer pipes and ditches through most of the developed portions of the City. These generally outlet into watercourses and waterbodies and ultimately into Bear Creek, which is the primary watercourse bisecting the City from north to south. Other important watercourses and waterbodies in the area include Bear Lake, Hughes Lake, Hermit Lake, Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Flyingshot Lake, Crystal Lake, Clairmont Lake, Woody Channel, and Wood Lake, amongst others. The City’s storm drainage system consists of about: • 226 km of storm pipes: ▪ 51% are 450mm in diameter or less, 13% are 1200mm in diameter or larger, the largest pipe is a 2300mm pipe; ▪ 50% of the piped system is less than 25 years old, and 12% is more than 50 years old with some of the oldest pipes nearing 80 years. ▪ About 43% of the pipes are made of PVC (mostly newer areas), 34% of concrete (generally the older areas), and 22% of CSP. • 18 km of catchbasin leads; • 2940 manholes, 1940 catchbasin manholes and 2470 catchbasins; • 97 storm outfalls: ▪ 64 of them discharge directly into Bear Creek, 16 in the Woody Channel (or its tributary), 8 in Crystal Lake, and 6 in the Flyingshot Lake drainage system. ▪ Outfalls along the Bear Creek Corridor have recently been assessed in great details, but there are no studies documenting the location and condition of the other storm outfalls. It is recommended that the City complete an outfall condition assessment study for all their outfalls. ▪ Of the 58 Bear Creek outfalls assessed, 14 outfalls have been classified as having major damage, 13 with moderate damage, 22 with minor damage, and 9 with no damage. The City should plan to repair these outfalls, with a focus on outfalls with major damage. • 43 stormwater management facilities: ▪ 25 are wet ponds and wetlands, 15 are dry ponds, and 3 are forebays (for water quality). There is also an additional wet pond on private development. • There are also areas of the city served by roadside and backlot swales and ditches, which includes about 530 individual culvert crossings. It is recommended that the City develop a comprehensive asset management system and drainage infrastructure inventory. This asset management system would be continuously updated and include a comprehensive inventory of existing drainage asset, their condition, cost of replacement and prioritization, amongst others.

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

RAINFALL DATA, FLOW MONITORING DATA AND WATER QUALITY The City owns and operates three rainfall gauges throughout the City. It is recommended that the City add two additional gauges (for a total of five) to better understand rainfall patterns and intensities throughout the City. From 2013 to 2017, there were seven rainfall events that exceeded a 2-year return period according to the City rain gauges: two in 2015, three in 2016 and two in 2017. Of note, a very extreme short-duration rainfall fell on most of the City on August 2, 2016. The rainfall was recorded as a 325-year 1-hour event to the north, a 75-year 1-hour event to the southeast and a 4-year 1-hour event to the west (based on the newly developed IDF curves). This event caused flooding at many locations in the City. This rainfall prompted the Government of Alberta to provide disaster relief funding to the affected residents. The City of Grande Prairie owns and operates four flow monitoring gauges installed in storm sewers throughout the City. The collected data was found to correlate well with the recorded rainfall data and with the calibrated hydraulic model. It is recommended that the City add two additional flow monitoring gauges (for a total of six) to their inventory to better characterize the storm runoff characteristics of different land use types in the various drainage basins of the City. Two locations for water quality measurements were identified, coinciding with the flow monitoring locations. The first location is upstream of the Canfor Ditch in Richmond Industrial Park; the second is downstream of the highway commercial area at 116 Avenue, west of 102 Street.

COMPUTER HYDRAULIC MODEL DEVELOPMENT For this storm drainage master plan update, a comprehensive dual-drainage computer model was developed to better understand the drainage system performance under extreme rainfall events, and to properly identify flood risk areas. To do this, the Cityâ&#x20AC;&#x2122;s drainage infrastructure was combined into a single Mike Urban hydraulic model. The model also includes a major drainage system component, including roads and other major drainage paths.

EXISTING DRAINAGE SYSTEM ASSESSMENT The existing drainage system of the City of Grande Prairie was evaluated (via the computer hydraulic model) under the newly developed 5-year 4-hour Chicago distribution rainfall event, the 100-year 4-hour Chicago distribution rainfall event and the 100-year 24-hour Chicago distribution rainfall event. Simulation results figures, showing the performance of the sewer and overland drainage systems, were produced, including ponding depth maps.

Sameng Inc.

III

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

The most at-risk areas of the City due to intense rainfall events are (in no particular order): 1- Northridge (southeast) – Residential / Commercial 2- Avondale / Montrose – Mostly Residential 3- Highland Park – Residential / Commercial 4- Mountview (west) and Crystal Ridge (southwest) – Residential 5- Crystal Heights and Ivy Lake Estates – Residential 6- Smith / Hillside (southeast) – Residential / Industrial 7- Patterson Place (southwest) – Residential 8- Country Club Estates – Residential 9- Richmond Industrial / College Park (southwest) – Industrial / Commercial 10- Gateway (south) – Commercial 11- Northgate (north) / Albinati Industrial – Industrial These eleven areas are primarily at risk of flooding due to a poor major drainage system (i.e. overland drainage). In other words, during an intense downpour, the storm sewer pipes are flowing at their maximum capacity and excess rainfall runoff is trapped on the ground surface until the sewer system regains capacity. Flooding in these areas is generally only of concern for rainfall events larger than the 1:5-year event. During a 5-year design rainfall event, an estimated 39% of the storm pipes will flow surcharged, and about 56% of the storm sewer system will be surcharged to less than 1 metre below ground. These are quite significant surcharges considering that the storm sewer system should flow within pipefull (no surcharge) during this rainfall event. The following stormwater management facilities are projected to overflow during the design 100-year 24-hour rainfall event: #4 (Mountview); #5 (Four Winds); #6 (Scenic Ridge); #10 (Crystal Village); #33 (Centre West #1); #38 (Vision West); # 40 (Kensington); and, #41 (Royal Oaks North). Of these 8 SWMFs, only the Mountview facility is projected to overflow to a point where residences in its vicinity may flood due to high water levels.

IMPROVEMENT CONCEPT PLANS FOR EXISTING DRAINAGE SYSTEM Drainage improvements were conceptualized for developed areas of the City that are at a higher risk of flooding, with a goal to achieve a 100-year level of flood protection. The individual improvements are too complex to be summarized here, but the general concept for all of them is to reduce, divert and/or convey storm runoff away from these flood-prone areas such that the ponding and flood risks are reduced to reasonable levels. This includes road/ground regrading, large diameter pipes, large capacity catchbasins, increase ditch capacity, increased culvert capacity, and more.

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

These improvements are grouped into five areas, as follows: • Northridge Area: will reduce flood risks in Northridge, Avondale / Montrose, Mountview (west) and Crystal Ridge (southwest). Estimated cost: $24.7 M. • Avondale / Montrose Area: will reduce flood risks in Avondale / Montrose, Mountview (west) and Crystal Ridge (southwest). Estimated cost: $23.2 M. • Highland Park / Swanavon Area: will reduce flood risks in Highland Park. Estimated cost: $14.3 M. • Ivy Lake / Cobblestone / Smith Area: will reduce flood risks in Smith / Hillside. Estimated cost: $11.0 M. • Richmond Industrial Area: will reduce flood risks in Richmond Industrial. Estimated cost: $25.3 M. The drainage improvement recommendations, which total about $98.5M, are aimed at providing a 100-year level of flood protection for the most at-risk areas of the City. Implementing nearly $100M of drainage upgrades would not be achievable in the short-term and would likely have to be spread over decades, mostly due to funding. As a result, it may be preferred to implement some drainage upgrades to at-least enhance the level of flood protection for each of these areas. It is recommended that additional conceptual studies be completed to further investigate the drainage issues and refine the improvements for these at-risk areas. For example, it may be possible to achieve a 25-year level of flood protection for all these areas for less than 50% of the cost of achieving a 100-year level of flood protection. A prioritization plan should also be developed, and benefits well understood. STORM DRAINAGE MASTER PLAN FOR FUTURE DEVELOPMENT AREAS A Storm Drainage Master Plan for future development areas was developed. The plan identifies nineteen (19) watersheds with distinct challenges and opportunities with respect to hydrology, economics, and environmental protection. Individual watershed studies will help determine pre-development flow rates, protect environmentally sensitive areas, and reserve critical drainage corridors for each area. To reduce the number, size, and construction costs of stormwater management facilities, the Master Plan focus on the establishment of ‘Water Retention and Conveyance Corridors’ along natural or existing drainage routes, especially around environmentally sensitive areas. The master plan identifies 29 natural areas that may be enhanced for stormwater retention, as well as 54 artificial stormwater management facilities, including some already approved under existing development plans. Most stormwater management facilities recommended under the master plan are “wet pond” types that are most common for urban developments. “Dry pond” facilities are recommended around the regional airport to avoid attracting waterfowl. Where drainage is to natural areas that are to be preserved, constructed forebays are recommended to manage water quality and control pollution. The requirement to limit runoff to 5 L/s/ha may be relaxed for some facilities, based on the type and the findings of future watershed studies. Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table of Contents Executive Summary................................................................................................................ I Table of Contents .................................................................................................................... i List of Appendices .................................................................................................................. v List of Figures ........................................................................................................................ vi List of Tables ......................................................................................................................... ix Corporate Authorization .......................................................................................................... x Acknowledgements ............................................................................................................... xi 1.0

Introduction ................................................................................................................1.1 Project Overview ................................................................................................................... 1.1 Project Location ..................................................................................................................... 1.1 Land Use Plan ....................................................................................................................... 1.1 Project Objectives .................................................................................................................. 1.2

2.0

Data Collection and Review........................................................................................2.1 Overview ................................................................................................................................ 2.1 Previous Storm Drainage Master Plans ................................................................................ 2.1 Bear Creek Studies and Projects .......................................................................................... 2.1 Outfall Studies and Projects .................................................................................................. 2.2 Woody Channel Studies and Projects ................................................................................... 2.3 Other Drainage Studies and Projects .................................................................................... 2.3 Environmental Studies ........................................................................................................... 2.4 Transportation Studies and Projects ..................................................................................... 2.4 Rehabilitation / Upgrading Projects ....................................................................................... 2.4 Planning Documents ............................................................................................................. 2.5 2.10.1 General ................................................................................................................................. 2.5 2.10.2 Municipal Development Plan (MDP) C-1237 (January 25, 2010) ......................................... 2.5 2.10.3 Intermunicipal Development Plan (IDP) C-1248 (June 14, 2010) ........................................ 2.5 2.10.4 Area Structure Plan (ASP) .................................................................................................... 2.5 2.10.5 Area Redevelopment Plan (ARP) ......................................................................................... 2.6 2.10.6 Outline Plan (OP) ................................................................................................................. 2.6 Drainage System Data .......................................................................................................... 2.7 Rainfall and Flow Monitoring Data ........................................................................................ 2.7 Historical Flood Records ....................................................................................................... 2.7 Other Collected Data ............................................................................................................. 2.8 Coordinate System ................................................................................................................ 2.8

3.0

Review of Municipal Development Standards .............................................................3.1 Overview ................................................................................................................................ 3.1 Recommended Changes to Current Design Standards ........................................................ 3.1 3.2.1 Section 1. - General .............................................................................................................. 3.1 3.2.2 Section 2.1 - Composition and Control ................................................................................. 3.1 3.2.3 Section 2.2 – Rainfall Intensity-Duration-Frequency ............................................................ 3.1 3.2.4 Section 2.3 - Storm Catchment Calculations ........................................................................ 3.4 3.2.5 Section 2.6 – Manning’s Formula “N” Value ......................................................................... 3.7 3.2.6 Section 2.12 – Manhole Detail and Location ........................................................................ 3.7

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1) 3.2.7 3.2.8 3.2.9 3.2.10 3.2.11 3.2.12

City of Grande Prairie

Section 3.4 – Inlet / Outlet Control Devices .......................................................................... 3.7 Section 4.3 – Engineering Drawing Requirements ............................................................... 3.8 Section 4.4 – Design Details for Wet Ponds......................................................................... 3.8 Section 4.5 – Design Details for Constructed Wetlands ....................................................... 3.8 Section 4.6 – Design Details for Dry Ponds ......................................................................... 3.9 Section 4.7 – Design Details for Drainage Parkways ........................................................... 3.9

Additional Recommendations to Design Standards .............................................................. 3.9 Water Quality Control Facility Design and Monitoring .......................................................... 3.9 Lot-Level Best Management Practices ............................................................................... 3.10

3.3.1 3.3.2

4.0

Existing Drainage System...........................................................................................4.1 Overview ................................................................................................................................ 4.1 Topography ........................................................................................................................... 4.1 Major Drainage Basins and Drainage Features .................................................................... 4.1 4.3.1 Overview ............................................................................................................................... 4.1 4.3.2 Bear Creek ........................................................................................................................... 4.2 4.3.3 Grande Prairie Reservoir ...................................................................................................... 4.3 4.3.4 Bear Lake ............................................................................................................................. 4.3 4.3.5 Hughes Lake and Downstream Conveyance ....................................................................... 4.3 4.3.6 Hermit Lake, Flyingshot Lake and Downstream Conveyance .............................................. 4.3 4.3.7 Crystal Lake and Downstream Conveyance ........................................................................ 4.4 4.3.8 Unnamed Well-Defined Watercourse Northeast of City ....................................................... 4.4 4.3.9 Clairmont Lake ..................................................................................................................... 4.4 4.3.10 Woody Channel .................................................................................................................... 4.5 4.3.11 Wood Lake and Downstream Conveyance .......................................................................... 4.5 Existing Stormwater Conveyance System ............................................................................ 4.6 4.4.1 General ................................................................................................................................. 4.6 4.4.2 Drainage Asset Management ............................................................................................... 4.6

5.0

4.4.2.1 4.4.2.2 4.4.2.3 4.4.2.4 4.4.2.5

Overview.............................................................................................................................. 4.6 Storm Sewer Pipes .............................................................................................................. 4.6 Manholes and Catchbasin Manholes ................................................................................... 4.7 Other Drainage Infrastructure .............................................................................................. 4.8 Drainage Asset Management Recommendations ............................................................... 4.8

4.4.8.1 4.4.8.2 4.4.8.3 4.4.8.4

Overview............................................................................................................................ 4.18 Pond Types ....................................................................................................................... 4.21 Natural Water Features ..................................................................................................... 4.21 Control Structures .............................................................................................................. 4.22

4.4.3 4.4.4 4.4.5 4.4.6 4.4.7 4.4.8

Piped Network ...................................................................................................................... 4.9 Storm Outfalls ..................................................................................................................... 4.11 Ditch Network ..................................................................................................................... 4.16 Major Drainage Channels ................................................................................................... 4.16 Catchbasins ........................................................................................................................ 4.17 Stormwater Management Facilities (SWMFs) .................................................................... 4.18

4.4.9

Quality Treatment Devices ................................................................................................. 4.23

Rainfall and Flow Monitoring Data Analysis and Recommended Monitoring Program 5.1 Overview ................................................................................................................................ 5.1 Precipitation Normal .............................................................................................................. 5.1 Rainfall ................................................................................................................................... 5.2 5.3.1 Rainfall Gauge Location and Data Availability...................................................................... 5.2 5.3.2 Data Quality Assurance ........................................................................................................ 5.3 5.3.3 Summary of Rainfall Data from 2013 to 2017 ...................................................................... 5.4 5.3.4 Recent Significant Rainfall Events ...................................................................................... 5.10 Flow Monitoring ................................................................................................................... 5.16 5.4.1 Flow Monitoring Gauge Location and Data Availability ...................................................... 5.16 5.4.2 Summary of Flow Monitoring Data from 2013 to 2017 ....................................................... 5.17 5.4.3 Recent Significant Rainfall Runoff Events .......................................................................... 5.23

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Recommended Rainfall and Flow Monitoring Program ....................................................... 5.33 Additional Recommendations .............................................................................................. 5.33

6.0

Computer Hydraulic Model Development ...................................................................6.1 Previous Computer Modeling Efforts ..................................................................................... 6.1 Computer Modeling Overview ............................................................................................... 6.1 Selection of Computer Model Software ................................................................................. 6.2 Network Model ....................................................................................................................... 6.3 6.4.1 Minor Drainage System ........................................................................................................ 6.3 6.4.2 Major Drainage System ........................................................................................................ 6.4 6.4.3 Major â&#x20AC;&#x201C; Minor System Integration ......................................................................................... 6.4 6.4.4 Stormwater Management Facilities and Control Structures ................................................. 6.5 6.4.5 Outfalls in Receiving Waterbodies/watercourses ................................................................. 6.5 Runoff Model ......................................................................................................................... 6.6 Summary of Physical Model Elements .................................................................................. 6.7 Model Calibration and Validation ........................................................................................... 6.8 6.7.1 Overview ............................................................................................................................... 6.8 6.7.2 Calibration / Validation Results............................................................................................. 6.8

7.0

Existing Drainage System Assessment ......................................................................7.1 Simulation Results ................................................................................................................. 7.1 Overview of Simulation Result Figures ................................................................................. 7.1 Minor Drainage System ........................................................................................................ 7.1 Major Drainage System ........................................................................................................ 7.1 Flood Risk Assessment ......................................................................................................... 7.2 Stormwater Management Facility Performance .................................................................... 7.4 Simulation Result Description ............................................................................................... 7.6 7.4.1 5-year 4-hour Chicago Distribution Rainfall Event ................................................................ 7.6 7.4.2 100-year 4-hour Chicago Distribution Rainfall Event ............................................................ 7.8 7.4.3 100-year 24-hour Chicago Distribution Rainfall Event .......................................................... 7.9 Detailed Assessment of High Flood Risk Areas .................................................................. 7.10 7.1.1 7.1.2 7.1.3

8.0

Improvement Concept Plans for Existing Drainage System ........................................8.1 Overview ................................................................................................................................ 8.1 Review of 2013 Storm Drainage Master Plan Recommendations ........................................ 8.1 Improvement Concepts by Area ............................................................................................ 8.3 8.3.1 Northridge Area (North-Central) ........................................................................................... 8.3 8.3.2 Avondale / Montrose Area (North-Central) ........................................................................... 8.4 8.3.3 Highland Park / Swanavon Area (Central) ............................................................................ 8.6 8.3.4 Ivy Lake / Cobblestone / Smith Area (Central-East) ............................................................. 8.6 8.3.5 Richmond Industrial Area (Central-West) ............................................................................. 8.7 Benefits .................................................................................................................................. 8.9 8.4.1 Overview ............................................................................................................................... 8.9 Cost Estimates .................................................................................................................... 8.10 Recommendations ............................................................................................................... 8.10

9.0

Storm Drainage Master Plan for Future Development Areas ......................................9.1 Objectives of Storm Drainage Master Plan ........................................................................... 9.1 Overview of Previous Storm Drainage Master Planâ&#x20AC;&#x2122;s Drainage Concepts for Future Servicing Areas ..................................................................................................................... 9.1 Receiving System Capacities ................................................................................................ 9.2 Environmental Considerations............................................................................................... 9.2

Sameng Inc.

iii

Storm Drainage Master Plan 2018 Final Report (Revision 1) 9.4.1 9.4.2 9.4.3 9.4.4 9.4.5

City of Grande Prairie

General ................................................................................................................................. 9.2 Environmental Protection and Enhancement Act (EPEA) .................................................... 9.3 Water Act .............................................................................................................................. 9.3 Public Lands Act ................................................................................................................... 9.4 Federal Legislation ............................................................................................................... 9.4

Stormwater Management Planning ....................................................................................... 9.4 General ................................................................................................................................. 9.4 Approach .............................................................................................................................. 9.4 Stormwater Management Facility Types .............................................................................. 9.5 Conveyance and Connectivity .............................................................................................. 9.7 Urban and Rural Cross Sections .......................................................................................... 9.8 Other End-of-Pipe Options ................................................................................................... 9.8 Runoff and Storage Estimations ........................................................................................... 9.8 Land Use ............................................................................................................................... 9.9 9.6.1 General ................................................................................................................................. 9.9 9.6.2 Grande Prairie Airport ........................................................................................................... 9.9 Environmentally Sensitive Areas ........................................................................................... 9.9 Stormwater Quality .............................................................................................................. 9.10 Future Stormwater Management Watersheds .................................................................... 9.10 9.9.1 Watershed “A” – Bear Lake Basin ...................................................................................... 9.12 9.9.2 Watersheds “B” and “C’ – Northwest Bear Creek ............................................................... 9.13 9.9.3 Watershed “D” – Highway 43X ........................................................................................... 9.14 9.9.4 Watershed “E” – South of Highway 43X ............................................................................. 9.15 9.9.5 Watershed “F” – Hermit Lake ............................................................................................. 9.16 9.9.6 Watershed “G” – Flyingshot Lake/Wetland......................................................................... 9.17 9.9.7 Watershed “K” – Kensington Development ........................................................................ 9.18 9.9.8 Watershed “H” – Hughes Lake ........................................................................................... 9.19 9.9.9 Watershed “I” – North of Airport ......................................................................................... 9.20 9.9.10 Watershed “J” – Linear Drainage Parkway. ........................................................................ 9.21 9.9.11 Watershed “V” – Hidden Valley and Northwest ASPs ........................................................ 9.22 9.9.12 Watershed “L” – Crystal Lake Basin ................................................................................... 9.23 9.9.13 Watersheds “M” and “N” – Northeast ASP ......................................................................... 9.24 9.9.14 Watershed “P” – Unnamed Creek ...................................................................................... 9.26 9.9.15 Watershed “Q” – West Carriage Lanes .............................................................................. 9.27 9.9.16 Watershed “R” – Woody Channel/84 Street ....................................................................... 9.28 9.9.17 Watershed “W” – Wood Lake Basin ................................................................................... 9.29 Implementation and Costs ................................................................................................... 9.30 9.10.1 Watershed Studies ............................................................................................................. 9.30 9.10.2 Public Easements and Interim Drainage Plans .................................................................. 9.30 9.10.3 Value Added ....................................................................................................................... 9.30 Stakeholder and Public Consultation .................................................................................. 9.31 9.5.1 9.5.2 9.5.3 9.5.4 9.5.5 9.5.6 9.5.7

10.0 Conclusions and Recommendations ........................................................................10.1

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

List of Appendices Appendix A: Design Rainfall Assessment Memo (February 20, 2018) Appendix B: Memo â&#x20AC;&#x201C; Flow and Rainfall Monitoring Memo (March 26, 2018) Appendix C: Stormwater Management Facility Summary Sheets Appendix D: Detailed Assessment of High Flood Risk Areas Appendix E: Conceptual Cost Estimates Appendix F: Stakeholder Open House Summary Report â&#x20AC;&#x201C; May 9, 2018 Appendix G: Computer Model of Storm Drainage System

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

List of Figures Figure 1-1: Location Plan....................................................................................................1.3 Figure 1-2: Neighbourhood Map and Important Areas ........................................................1.4 Figure 1-3: Planning Information.........................................................................................1.5 Figure 1-4: Current Land Use Plan .....................................................................................1.6 Figure 1-5: Future Land Use Plan .......................................................................................1.7 Figure 3-1: Current City of Grande Prairie IDF Curves........................................................3.3 Figure 3-2: Proposed Updates to City of Grande Prairie IDF Curves ..................................3.3 Figure 3-3: Current (left) and New (right) City of Grande Prairie 4-Hour Chicago Distribution Design Rainfalls .............................................................................3.6 Figure 3-4: New City of Grande Prairie 24-Hour Chicago (top), 12-Hour Huff (left) and 24-Hour Huff (right) Distribution Design Rainfalls .............................................3.6 Figure 4-1: Summary of Storm Pipes by Diameter and Material .........................................4.9 Figure 4-2: Summary of Storm Pipes by Installation Year and Material ............................4.10 Figure 4-3: SWMF in the City of Grande Prairie over the Years ........................................4.18 Figure 4-4: Topography and Major Basins (City Area) ......................................................4.24 Figure 4-5: Topography and Major Basins (Around City) ..................................................4.25 Figure 4-6: Existing Drainage Network / Pipe Size ............................................................4.26 Figure 4-7: Pipe Age.........................................................................................................4.27 Figure 4-8: Pipe Material ..................................................................................................4.28 Figure 4-9: Existing Outfalls and Tributary Sewer Pipes ...................................................4.29 Figure 4-10: Catchbasin Distribution .................................................................................4.30 Figure 4-11: Existing Storm Water Management Facilities ................................................4.31 Figure 5-1: Temperature and Precipitation Graph for 1981 to 2010 Canadian Climate Normals for the Grande Prairie Airport (from climate.weather.gc.ca) ................5.1 Figure 5-2: Rainfall Data for the Year 2013 at RG1 and RG2 of the City of Grande Prairie .5.5 Figure 5-3: Rainfall Data for the Year 2014 at RG1 and RG2 of the City of Grande Prairie .5.6 Figure 5-4: Rainfall Data for the Year 2015 at RG1 and RG2 of the City of Grande Prairie .5.7 Figure 5-5: Rainfall Data for the Year 2016 at RG1, RG2 and RG3 of the City of Grande Prairie ...............................................................................................................5.8 Figure 5-6: Rainfall Data for the Year 2017 at RG1, RG2 and RG3 of the City of Grande Prairie ...............................................................................................................5.9 Figure 5-7: Rainfall Data for the June 19 to 20, 2015 Rainfall Event (peak: 20-yr 12-hr event) .............................................................................................................5.12 Figure 5-8: Rainfall Data for the June 22, 2015 Rainfall Event (peak: 4-yr 30-min event) .5.12

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-9: Rainfall Data for the June 14 to 17, 2016 Rainfall Event (peak: 7-yr 24-hr event) .............................................................................................................5.13 Figure 5-10: Rainfall Data for the August 2, 2016 Rainfall Event (peak: 325-yr 1-hr event)5.13 Figure 5-11: Rainfall Data for the August 21 to 22, 2016 Rainfall Event (peak: 5-yr 1-hr event) .............................................................................................................5.14 Figure 5-12: Rainfall Data for the May 23 to 24, 2017 Rainfall Event (peak: 5-yr 12-hr event) .............................................................................................................5.14 Figure 5-13: Rainfall Data for the September 18 to 20, 2017 Rainfall Event (peak: 4-yr 24-hr event) ....................................................................................................5.15 Figure 5-14: Measured Flow Monitoring Data for the Year 2013 .......................................5.18 Figure 5-15: Measured Flow Monitoring Data for the Year 2014 .......................................5.19 Figure 5-16: Measured Flow Monitoring Data for the Year 2015 .......................................5.20 Figure 5-17: Measured Flow Monitoring Data for the Year 2016 .......................................5.21 Figure 5-18: Measured Flow Monitoring Data for the Year 2017 .......................................5.22 Figure 5-19: Flow Monitoring Data (Measured Flow and Modeled Flow and Depth) for the June 19 to 21, 2015 Rainfall Event (peak: 20-yr 12-hr event) ...................5.26 Figure 5-20: Flow Monitoring Data (Measured Flow Only – Not Modeled) for the June 22, 2015 Rainfall Event (peak: 4-yr 30-min event) ................................................5.27 Figure 5-21: Flow Monitoring Data (Measured Flow and Depth Only – Not Modeled) for the June 14 to 17, 2016 Rainfall Event (peak: 7-yr 24-hr event) .....................5.28 Figure 5-22: Flow Monitoring Data (Measured Flow and Depth and Modeled Flow and Depth) for the August 2, 2016 Rainfall Event (peak: 325-yr 1-hr event) ..........5.29 Figure 5-23: Flow Monitoring Data (Measured Flow and Depth Only – Not Modeled) for the August 21 to 22, 2016 Rainfall Event (peak: 5-yr 1-hr event) ....................5.30 Figure 5-24: Flow Monitoring Data (Measured Flow and Depth and Modeled Flow and Depth) for the May 23 to 24, 2017 Rainfall Event (peak: 5-yr 12-hr event)......5.31 Figure 5-25: Flow Monitoring Data (Measured Flow and Depth and Modeled Flow and Depth) for the September 18 to 20, 2017 Rainfall Event (peak: 4-yr 24-hr event) .............................................................................................................5.32 Figure 5-26: Historical and Existing Rainfall and Flow Monitoring Gauge Locations .........5.35 Figure 5-27: Proposed Rainfall and Flow Monitoring Gauge Locations for 2018 Monitoring Season .........................................................................................5.36 Figure 6-1: Minor Drainage System Modeling Schematic .................................................6.13 Figure 6-2: Major Drainage System Modeling Schematic .................................................6.14 Figure 6-3: Storm Catchment Imperviousness Modeling Schematic .................................6.15 Figure 7-1: Flood Risk Areas in City of Grande Prairie due to 100-Year Rainfall.................7.3 Figure 7-2: Simulation Results – Existing System – 1:5-year 4-hour Event – Sewer Surcharge.......................................................................................................7.11 Sameng Inc.

vii

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 7-3: Simulation Results – Existing System – 1:5-year 4-hour Event – Theoretical Loading in Pipe...............................................................................................7.12 Figure 7-4: Simulation Results – Existing System – 1:5-year 4-hour Event – Surface Ponding ..........................................................................................................7.13 Figure 7-5: Simulation Results – Existing System – 1:5-year 4-hour Event – Peak Surface Flow Rate ..........................................................................................7.14 Figure 7-6: Simulation Results – Existing System – 1:100-year 4-hour Event – Sewer Surcharge.......................................................................................................7.15 Figure 7-7: Simulation Results – Existing System – 1:100-year 4-hour Event – Theoretical Loading in Pipe ............................................................................7.16 Figure 7-8: Simulation Results – Existing System – 1:100-year 4-hour Event – Surface Ponding ..........................................................................................................7.17 Figure 7-9: Simulation Results – Existing System – 1:100-year 4-hour Event – Peak Surface Flow Rate ..........................................................................................7.18 Figure 7-10: Simulation Results – Existing System – 1:100-year 24-hour Event – Sewer Surcharge.......................................................................................................7.19 Figure 7-11: Simulation Results – Existing System – 1:100-year 24-hour Event – Theoretical Loading in Pipe ............................................................................7.20 Figure 7-12: Simulation Results – Existing System – 1:100-year 24-hour Event – Surface Ponding ..........................................................................................................7.21 Figure 7-13: Simulation Results – Existing System – 1:100-year 4-hour Event – Peak Surface Flow Rate ..........................................................................................7.22 Figure 8-1: Overview of Drainage Improvement Concepts for Developed Areas...............8.12 Figure 8-2: Drainage Improvement Concepts for Northridge Area ....................................8.13 Figure 8-3: Drainage Improvement Concepts for Avondale / Montrose Area ....................8.14 Figure 8-4: Drainage Improvement Concepts for Highland Park / Swanavon Area ...........8.15 Figure 8-5: Drainage Improvement Concepts for Ivy Lake / Cobblestone / Smith Area .....8.16 Figure 8-6: Drainage Improvement Concepts for Richmond Industrial Area (Option 1) .....8.17 Figure 8-7: Drainage Improvement Concepts for Richmond Industrial Area (Option 2) .....8.18 Figure 8-8: Drainage Improvement Concepts for Richmond Industrial Area (Option 3) .....8.19 Figure 8-9: Drainage Improvement Concepts for Richmond Industrial Area (Option 4) .....8.20 Figure 8-10: Drainage Improvement Concepts for Richmond Industrial Area (Option 5) ...8.21 Figure 8-11: Simulation Results – Improved System – 1:100-year 4-hour Event – Sewer Surcharge.......................................................................................................8.22 Figure 8-12: Simulation Results – Improved System – 1:100-year 4-hour Event – Theoretical Loading in Pipe ............................................................................8.23 Figure 8-13: Simulation Results – Improved System – 1:100-year 4-hour Event – Surface Ponding ..........................................................................................................8.24 Sameng Inc.

viii

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 8-14: Simulation Results – Improved System – 1:100-year 4-hour Event – Peak Surface Flow Rate ..........................................................................................8.25 Figure 9-1: Stormwater Management Utilizing Natural/Constructed Wetlands ..................9.32 Figure 9-2: Naturalized Drainage Parkway Overview ........................................................9.33 Figure 9-3: Environmentally Sensitive Areas ....................................................................9.34 Figure 9-4: Future Development Plan Overview ...............................................................9.35 Figure 9-5: Future Development Plan Northwest ..............................................................9.36 Figure 9-6: Future Development Plan Southwest..............................................................9.37 Figure 9-7: Future Development Plan West ......................................................................9.38 Figure 9-8: Future Development Plan Northeast ...............................................................9.39 Figure 9-9:Future Development Plan Southeast ...............................................................9.40

List of Tables Table 3-1: Storm Drainage Design Standards Review ......................................................3.11 Table 4-1: Summary of Storm Sewer Outfalls ...................................................................4.13 Table 4-2: Summary of Stormwater Management Facilities ..............................................4.19 Table 5-1: Summary of City of Grande Prairie Rainfall Gauges ..........................................5.2 Table 5-2: Summary of Rainfall Events Exceeding a 1:2-Year Return Period in the City of Grande Prairie from 2013 to 2017 ..................................................................5.11 Table 5-3: Summary of City of Grande Prairie Flow Monitoring Gauges ...........................5.16 Table 5-4: Summary of Flow Monitoring Data for Rainfall Event Exceeding a 1:2-Year Return Period in the City of Grande Prairie from 2013 to 2017 .......................5.24 Table 6-1: Kinematic Wave Parameters (Horton Parameters) for Storm Catchments .........6.6 Table 6-2: Approximate Runoff Coefficient for Catchment Areas of Various Imperviousness ................................................................................................6.7 Table 7-1: Flood Risk Quantification Table .........................................................................7.2 Table 7-2: Modeling Results of Stormwater Management Facilities ....................................7.5 Table 8-1: Conceptual Costs Summary ............................................................................8.10 Table 9-1: Applicability of Stormwater Management Facility Types ....................................9.5 Table 9-2: Summary of Watersheds in Future Servicing Plan ...........................................9.11

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Acknowledgements We wish to thank those who contributed time and knowledge to the development of this study including, but not limited to, the following:

CITY OF GRANDE PRAIRIE • Richard Sali, C.E.T. • Mike Harvard, M.A.Sc., E.I.T. • Jennifer Comeau, C.E.T.

SAMENG INC. • David Yue, P.Eng. • Maxime Bélanger, M.Sc., P.Eng. • Nathan Forsyth, P.Eng. • Jianan Cai, Ph.D. • Brandon Rivet, C.E.T. • Jared Nicholas, C.E.T.

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

1.0

City of Grande Prairie

Introduction Project Overview

Sameng Inc. (Sameng) was retained by the City of Grande Prairie (City) in November 2017 to undertake an update to its Storm Drainage Master Plan. The last update to the Master Plan was in 2012-13. Previous versions of the Master Plan were completed in 2004 and 1995. In the last decade, the City’s population has grown by an estimated 34% to a total of about 63,000 residents (from 2016 Municipal Census). According to the City’s 2008 Growth Study, population in Grande Prairie is projected to reach 80,000 by 2028 and 100,000 by 2038. This growth has resulted in many new neighbourhoods and developments within the City, with many more being planned in the years to come. This causes an increase in stormwater runoff and the need to effectively manage the runoff being discharged to receiving watercourses. Furthermore, effective January 1, 2016, the City of Grande Prairie received 6,316 ha of land from the County of Grande Prairie No.1 following annexation. The City now covers an area of 13,658 ha. This is the first Storm Drainage Master Plan since the recent annexation happened, although the 2012-13 Master Plan did include this annexation area as part of its study area. An updated drainage plan is needed to support growth in these newly annexed areas. Project Location Grande Prairie is a City in northwest Alberta, Canada, in the heart of the Peace Region. It is located approximately 465 km northwest of Edmonton at the intersection of Highway 43 and Highway 40 at Latitude 55.17N and Longitude 118.79W. The City is surrounded by the County of Grande Prairie No. 1, which includes the Hamlet of Clairmont just north of the City. A location plan is shown in Figure 1-1. A map showing the current City neighbourhoods and key areas is shown in Figure 1-2. Figure 1-3 shows the area structure plans, outline plans and area redevelopment plans in effect in the City; they are listed in Section 2.10. Land Use Plan Figure 1-4 shows a simplified version of the current land use plan in the City (Bylaw C1260). Figure 1-5 shows the Future Land Use Plan according to the City’s Municipal Development Plan (MDP – Bylaw C-1237). • Existing Development (Figure 1-4): Most of the City is residential with some small commercial and public service/institution nodes scattered all around. The main commercial areas are focused around Highway 43 north and west of the City. The main industrial areas are west of the City, with a few other industrial nodes north of the City and east of the railroad tracks east of Resources Road. The Grande Prairie

Sameng Inc.

1.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Airport is located to the northwest of the City. The Bear Creek area is surrounded by a recreational open space. • Future Development Areas (Figure 1-5): The MDP suggests that future commercial/industrial developments will focus along the northwest and northeast of the City. Residential areas will mostly extend from the existing residential areas to the east and south of the City and will cover a large portion of land to the northwest near the Bear Creek Corridor and near Hermit Lake and Bear Lake. The area near the intersection of 100 Avenue and 100 Street is designated as the Central Business District where some of the higher density residential and commercial office sites are planned. Project Objectives The main goal of this project is to provide a comprehensive review of the City’s existing drainage design standards, examine issues with the existing drainage system and identify upgrades to mitigate these issues, and develop an effective long-term drainage plan to allow future development to proceed. The key project objectives are as follows: • Review of Municipal Development Standards, including engineering design guidelines, stormwater management criteria, servicing requirements and design storm review. (Section 3.0). • Provide comprehensive description of the City’s existing drainage system (Section 4.0). • Review and assess recently collected rainfall and flow monitoring data, and develop a rainfall and flow monitoring program for the years to come (Section 5.0). • Develop comprehensive computer model of the entire City’s drainage system, including major (i.e. surface) and minor (i.e. sewers) drainage systems, such that flood risk areas and drainage system deficiencies can be well identified and understood. (Section 6.0). • Assess the performance of the current drainage system and identify constraints with the existing system. (Section 7.0). • Develop conceptual improvement recommendations to mitigate flooding in at-risk areas. (Section 8.0). • Develop a stormwater management concept plan for future development areas of the City. Complete stakeholder consultations and open houses in support of this activity. (Section 9.0). .

Sameng Inc.

1.2

LEGEND CURRENT CITY BOUNDARY (INCL: JAN 1, 2016 ANNEXATION) PREVIOUS CITY BOUNDARY (PRE 2016) WATERCOURSE / WATERBODY EXISTING RAILROAD EXISTING HIGHWAY

HIGHWAY 2

FUTURE HIGHWAY

CLAIRMONT LAKE

BEAR CREEK

BEAR LAKE

HIGHWAY 43X

TWP RD 722

HIGHWAY 43

HAMLET OF CLAIRMONT

HERMIT LAKE

SECONDARY HIGHWAY 670 (132 AVENUE) EE

HIGHWAY 43X

HUGHES LAKE

108 STREET

TWP RD 720

CRYSTAL LAKE

A BE

116 AVENUE

EK RE RC

GRANDE PRAIRIE

GRANDE PRAIRIE AIRPORT

RGE RD 53

RGE RD 55

92 STREET

RGE RD 54

100 AVENUE

100 STREET

116 STREET

124 STREET

RGE RD 70

RGE RD 71

HIGHWAY 43 (100 AVENUE)

HIGHWAY 40 (108 STREET)

HIGHWAY 43

108 AVENUE RESERVOIR

WOOD LAKE

84 AVENUE

OAD

E URC

O RES

TWP RD 712

68 AVENUE CR E BE

RGE RD 65

NOTE: AIRPHOTO DATED 2016 Prepared By:

FLYINGSHOT LAKE

EEK

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

BEAR CR

TWP RD 710

HIGHWAY 40

BEAR CREEK

Client:

Project:

Storm Drainage Master Plan 2018 Title:

Location Plan Scale:

Figure:

N.T.S.

1-1

148 AVENUE

LEGEND CITY BOUNDARY PROPERTY LINE CITY NEIGHBOURHOOD BOUNDARY

BEAR CREEK GOLF CLUB

BEAR CREEK HIGHLANDS

TRADER RIDGE

ARBOUR HILLS

A BE

TWP RD 720

ALBINATI INDUSTRIAL

WATERCOURSE / WATERBODY

LAKELAND

NORTHGATE

EE CR

CRYSTAL LAKE ESTATES

ROYAL OAKS

NORTHRIDGE

100 STREET

HIDDEN VALLEY

HUGHES LAKE

132 AVENUE

CRYSTAL RIDGE

CRYSTAL LAKE

HOSPITAL

HOSPITAL (FUTURE)

FIRE HALL

POLICE STATION

KINGSGATE

COPPERWOOD

F C AR BE EK RE

AVONDALE

MOUNTVIEW CRYSTAL HEIGHTS TRUMPETER VILLAGE

RIVERSTONE EAGLE ESTATES

CR EE AR

LAKE

COUNTRY CLUB WEST

COUNTRY CLUB ESTATES

IEN O'BR

STONE RIDGE

O'BRIEN LAKE

AQUATERA WATER AND WASTEWATER TREATMENT PLANT

GRANDE PRAIRIE GOLF COURSE AND COUNTRY CLUB

SIGNATURE FALLS

COUNTRYSIDE SOUTH

OAD

COUNTRYSIDE NORTH

R CES

68 AVENUE

FLYINGSHOT LAKE

FIELDBROOK

NOTE: THIS FIGURE IS A SIMPLIFIED REPRESENTATION OF THE CURRENT NEIGHBOURHOODS AND IMPORTANT AREAS IN AND AROUND THE CITY OF GRANDE PRAIRIE. REFER TO THE CITY GRANDE PRAIRIE FOR UPDATED INFORMATION Prepared By:

OUR

SOUTH PATTERSON PLACE

COMMUNITY KNOWLEDGE CAMPUS

CRYSTAL LANDING

84 STREET

COBBLESTONE

CREEKSIDE

116 STREET

124 STREET

RGE RD 65

F PATTERSON PLACE

RES

MISSION HEIGHTS

TWP RD 712

RAILWAY INDUSTRIAL

84 AVENUE

WESTPOINTE

PINNACLE RIDGE

HIGHLAND PARK

TOW

RGE RD 70

CANFOR INDUSTRIAL

RAIL

KENSINGTON

SMITH

RICHMOND INDUSTRIAL PARK

RAILSIDE BUSINESS PARK

100 AVENUE 92 STREET

CENTRAL WEST BUSINESS PARK F

IVY LAKE ESTATES

KENNEDY

AIRPORT INDUSTRIAL

CENTRAL BUSINESS DISTRICT

SWANAVON

VISION WEST BUSINESS PARK

COLLEGE PARK

SOUTHVIEW

MOUNTVIEW BUSINESS PARK

HILLSIDE

GRANDE PRAIRIE REGIONAL COLLAGE

100 AVENUE

WEST MOUNTVIEW INDUSTRIAL

GATEWAY

108 STREET

NORDHAGEN

WESTGATE

FAIRWAY

BROCHU INDUSTRIAL

WEST CARRIAGE LANE

108 AVENUE RESERVOIR

MEADOWVIEW

WEST TERRA

SWAN CITY

AIRPORT

116 AVENUE VLA MONTROSE

GRANDE PRAIRIE AIRPORT

SUMMERSIDE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Project:

Storm Drainage Master Plan 2018 Title:

Neighbourhood Map and Important Areas

Scale:

Figure:

1:40,000

1-2

HIGHWAY 2

LEGEND CITY BOUNDARY PROPERTY LINE

BEAR CREEK

CLAIRMONT LAKE

BEAR LAKE

LAKE EXISTING HIGHWAY FUTURE HIGHWAY HIGHWAY 43X

TWP RD 722

AREA STRUCTURE PLAN (ASP)

HIGHWAY 43

AREA REDEVELOPMENT PLAN (ARP)

HIGHWAY 43

OUTLINE PLAN (OP)

08 03

148 AVENUE

HERMIT LAKE

AR EE CR

06 100 STREET

HIGHWAY 43X

HUGHES LAKE

SECONDARY HIGHWAY 670

132 AVENUE

TWP RD 720

37 C AR BE

116 AVENUE

EK RE

CRYSTAL LAKE

108 AVENUE

03 11

01 02 04

20 05

108 STREET

84 AVENUE

WOOD LAKE

Prepared By:

R CES

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

OAD

Client:

68 AVENUE

28 K

19 AKE IEN L O'BR

CR EE

BE AR

FLYINGSHOT LAKE

21 TWP RD 712

OUR

HIGHWAY 40

116 STREET

124 STREET

RES

RGE RD 65

RGE RD 70

Project:

Storm Drainage Master Plan 2018

REEK

BEAR C

Title:

Planning Information

BEAR CREEK

TWP RD 710

HIGHWAY 40

RGE RD 71

TWP RD 714

100 AVENUE

RGE RD 53

100 AVENUE

RESERVOIR

RGE RD 54

84 STREET

92 STREET

HIGHWAY 43

Scale:

Figure:

1-3

LEGEND

CLAIRMONT LAKE

BEAR CREEK

CITY BOUNDARY

BEAR LAKE

PROPERTY LINE WATERCOURSE / WATERBODY LAKE

TWP RD 722

LAND USE LEGEND RESIDENTIAL PUBLIC SERVICE 148 AVENUE

COMMERCIAL INDUSTRIAL MUSKOSEEPI PARK DIRECT CONTROL URBAN RESERVE

HERMIT LAKE

AIRPORT DISTRICT

132 AVENUE

AR BE

TWP RD 720

RURAL SERVICE AREA

HUGHES LAKE

100 STREET

AIRPORT VICINITY OVERLAY CRYSTAL LAKE

BE AR

116 AVENUE

CR K

108 AVENUE RESERVOIR

TWP RD 714

108 STREET

116 STREET

124 STREET

84 AVENUE

84 STREET

RGE RD 54

NOTE: THIS FIGURE IS A SIMPLIFIED REPRESENTATION OF THE CURRENT LAND USE ZONING IN THE CITY OF GRANDE PRAIRIE. REFER TO CITY OF GRANDE PRAIRIE FOR UPDATED INFORMATION

WOOD LAKE

Prepared By: CES

OUR

RES

RGE RD 65

RGE RD 70

RGE RD 71

92 STREET

100 AVENUE

RGE RD 53

100 AVENUE

D ROA

68 AVENUE

FLYINGSHOT LAKE

Client: CR AR

A IEN L O'BR

TWP RD 712

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Project:

Storm Drainage Master Plan 2018

REEK BEAR C

BEAR CREEK

Title:

Current Land Use Plan TWP RD 710

Scale:

Figure:

N.T.S. SP R

ING

EE K

1-4

LEGEND

CLAIRMONT LAKE

BEAR CREEK

CITY BOUNDARY

BEAR LAKE

PROPERTY LINE WATERCOURSE / WATERBODY LAKE

TWP RD 722

LAND USE LEGEND RESIDENTIAL PUBLIC SERVICE / INSTITUTIONAL 148 AVENUE

COMMERCIAL INDUSTRIAL COMMERCIAL / INDUSTRIAL CENTRAL BUSINESS DISTRICT RECREATIONAL OPEN SPACE

HERMIT LAKE

AIRPORT

132 AVENUE

AR BE

TWP RD 720

EE CR

100 STREET

HUGHES LAKE

CRYSTAL LAKE

C AR BE

116 AVENUE

108 AVENUE RESERVOIR

TWP RD 714

108 STREET

116 STREET

124 STREET

84 AVENUE

RGE RD 54

84 STREET

NOTE: THIS FIGURE IS A SIMPLIFIED REPRESENTATION OF THE FUTURE LAND USE PLAN AS PER THE MUNICIPAL DEVELOPMENT PLAN (BYLAW C-1237). REFER TO CITY OF GRANDE PRAIRIE FOR UPDATED INFORMATION

WOOD LAKE

Prepared By: O RES

RGE RD 65

RGE RD 70

O ES R URC AD

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

68 AVENUE

FLYINGSHOT LAKE

IE O'BR

N LA

Client: CR EE K

TWP RD 712

BE AR

RGE RD 71

92 STREET

100 AVENUE

RGE RD 53

100 AVENUE

Project:

Storm Drainage Master Plan 2018

REEK

BEAR C

Title: BEAR CREEK

Future Land Use Plan Scale:

Figure:

TWP RD 710

N.T.S.

1-5

Storm Drainage Master Plan 2018 Final Report (Revision 1)

2.0

City of Grande Prairie

Data Collection and Review Overview

Many documents and information were reviewed through the course of this project. The following are some of the most relevant information that was collected/reviewed/used (in parts or entirely) for purposes of developing this storm drainage master plan. Previous Storm Drainage Master Plans Grande Prairie Storm Drainage Master Plan (Focus Corporation for City of Grande Prairie, December 2013) • Updates the 2004 Storm Drainage Master Plan. It includes a summary of existing storm infrastructure, review of operation and maintenance procedures, review of storm drainage system design standards, update to XPSWMM computer models (at completion of the 2013 Master Plan, there were 23 individual models), review of rainfall data and flow monitoring data, model calibration, existing stormwater drainage system analysis, recommendations to the existing storm drainage system, and stormwater management concept plan for future development areas. City of Grande Prairie Storm Drainage Master Plan (Associated Engineering for City of Grande Prairie, October 2004) • Updates the 1995 Storm Drainage Master Plan. It includes an assessment of the existing storm drainage system, review of stormwater management design criteria, development of a storm drainage system upgrading plan, development of a stormwater management concept plan for future development areas, and the review of operation and maintenance issues. Bear Creek Studies and Projects City of Grande Prairie Bear Creek Corridor Assessment – Figures 1 and 2 (DRAFT) (Matrix Solutions Inc., October 2017) • Shows the 100-year flood risk maps of Bear Creek at the upstream end (northwest) of the City from the City limits to Range Road 63 (116 Street). Grande Prairie Reservoir Feasibility Study (Golder Associates for City of Grande Prairie, February 2012) • Feasibility study of the Grande Prairie Reservoir along Bear Creek. The report summarizes the reservoir’s existing conditions, and describes the potential reservoir management plan, including the opportunities to manage the sediment while also

Sameng Inc.

2.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

improving the reservoir for other purposes including boating recreation and enhancing wildlife habitat. Bear Creek Corridor Geohazard Slope Stability and Erosion Assessment (Parkland Geotechnical Ltd. for City of Grande Prairie, August 2011) • Erosion and overall stability assessment as it relates to geohazard risk within the Bear Creek corridor, and highlight of potential areas of concern. A framework was developed based around an engineering evaluation of reasonable setback distances. City of Grande Prairie Flood Risk Mapping Study - Alberta Flood Risk Mapping Program (northwest hydraulic consultants for Alberta Environment, March 2007) • Flood risk mapping study for Bear River (Bear Creek) through the developed parts of the City, including the estimation of flood levels along the Bear River and the preparation of maps showing the 10-year and 100-year flood lines. Outfall Studies and Projects Stormwater Outfall Assessment along the Bear Creek within the City of Grande Prairie (DRAFT) (Westhoff Engineering Resources, Inc. for City of Grande Prairie, October 31, 2017) • Inspection of stormwater outfalls along Bear Creek to document existing outfall condition, assess outfall damage and identify its cause, and recommend next steps to rehabilitate erosion issues. Sixty-six (66) outfall sites were inspected. 2009 Bear Creek Corridor Outfall Inspection Report (Parkland Geotechnical Ltd. for City of Grande Prairie, March 2010) • This report documents the findings of the 2009 outfall inspection and assessment, including the identification of maintenance issues and recommendations, rehabilitation recommendations, further monitoring recommendations or rehabilitation needs. A priority ranking was assigned based on the assessment findings. Drawings: ▪ Outfall Rehabilitation Program 2017 (2017) - Outfall #1 replacement to baffle structure; and replacement of pond inlet (SWMF #22). ▪ 2015 Bear Creek Outfall Rehabilitation (2015) - Outfall #24 and #37

Sameng Inc.

2.2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Woody Channel Studies and Projects North East Drainage Basin Study (Focus Corporation for City of Grande Prairie, August 2011). • Storm drainage study for the North East basin which is part of the Woody Channel Basin, with a goal to tie-together the existing and proposed storage and conveyance elements within the basin through to the discharge into the Woody Channel. This will allow individual developments to proceed in conformance with an overall drainage strategy for the area. Woody Creek Study – Resources Road to 68th Avenue (Beairsto, Lehners, Ketchum Engineering for City of Grande Prairie, November 2006) • Provides a detailed evaluation of the Woody Creek drainage basin within the City limits (from Resources Road to 68th Avenue), including recommendations to improve drainage conditions in the Creek to better serve existing and future developments. Other Drainage Studies and Projects Grande Prairie Richmond Industrial Park Storm Basin Study (Focus Corporation for City of Grande Prairie, December 2013) • The study provides an analysis of the Richmond Industrial Park Drainage Basin, provides an update to the XPSWMM stormwater model for the Richmond Industrial Park basin, and recommends solutions for mitigation of stormwater issues and flooding in the study area. Smith Storm Basin Study (Matrix Solutions Inc. for City of Grande Prairie, November 2016) • Hydrologic and hydraulic study of the stormwater management system within the Smith Storm Basin, including recommendations for addressing existing deficiencies and recommendations to service future development in the area. Drawings: • Existing Drainage Drawings for Grande Prairie Airport (First Submission Drawings dated 2006-10-17). • Richmond Industrial Storm Ponds (Helix Engineering Ltd. for City of Grande Prairie, Issued for Tender drawings dated March 2018)

Sameng Inc.

2.3

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Environmental Studies City of Grande Prairie Environmentally Significant Areas – Bear Creek and Crystal Lake within City-owned Lands – Riparian Health Summary Final Report (Alberta Riparian Habitat Management Society - Cows and Fish for City of Grande Prairie, January 2014) • Ground-based riparian health assessment and riparian habitat boundary delineation for select Ecologically Significant Areas (ESAs) in the City of Grande Prairie. This was a follow-up to the 2012 environmental study described below. City of Grande Prairie Mapping of Environmental Reserve (ER) and Science Based Setbacks for ER (O2 Planning + Design for City of Grande Prairie, September 2012) • Mapping of riparian areas, wetlands and other environmentally significant natural features, identification of priority conservation areas and identification of setbacks in the City of Grande Prairie. Transportation Studies and Projects Transportation Master Plan (2009) (ISL Engineering and Land Services for City of Grande Prairie, August 2011) • This Transportation Master Plan enables the city to adapt to future growth within and outside its current boundaries. It provides a long-term roadway network that enables the City to grow and accommodate growth in an orderly manner and updates the City’s Transportation Levy database. Drawings: • Highway 43X Grande Prairie Bypass (AECOM for Alberta Transportation, Issued for Construction dated 2016-11-04). Rehabilitation / Upgrading Projects Drawings: • 92 Street from 100 Avenue to 116 Avenue (2017) • 105th Avenue (102 Avenue Entrance Upgrade) (2016) • 2016/2017 Downtown Rehabilitation (2016) • 105th Avenue (Between 100th Street and Muskoseepi Park) (2015) • 124th Street Upgrades (100th Avenue to South City Limits) (2015) • 132 Avenue (102 St-116 St) & 108 Street Upgrades (2015)

Sameng Inc.

2.4

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Planning Documents 2.10.1 General Planning documents including Area Structure Plans (ASP), Outline Plans (OP), Area Redevelopment Plan (ARP), the City’s Municipal Development Plan (MDP) and the Intermunicipal Development Plan (IDP) provide information relating to proposed land use, proposed road alignment and proposed drainage servicing concepts for future development areas, amongst others. These documents were downloaded from the City of Grande Prairie website. The study area of these plans is illustrated in Figure 1-3 and listed below. 2.10.2 Municipal Development Plan (MDP) C-1237 (January 25, 2010) The MDP is a statutory plan whose primary intent is to provide a broad framework for the land use, growth and development of the City over the next 20 to 25 years. It provides the policy basis for Area Structure Plans (ASP's), Outline Plans (OP's), Area Redevelopment Plans (ARP's) and the Land Use Bylaw (LUB). 2.10.3 Intermunicipal Development Plan (IDP) C-1248 (June 14, 2010) This is a statutory plan formulated and adopted by both the City of Grande Prairie and the County of Grande Prairie No. 1. Its primary intent is to coordinate land use compatibility, economic development and servicing and transportation issues between the two municipalities. 2.10.4 Area Structure Plan (ASP) ▪ Arbour Hills ASP C-1212...................................... (January 12, 2009) ▪ Bear Creek Highlands ASP C-1201 ..................... (January 12, 2009) ▪ Country Club West ASP C-887 ............................ (April 30, 1990) ▪ Crystal Heights ASP C-896 .................................. (August 7, 1990) ▪ Crystal Lake Estates ASP C-766 ......................... (September 20, 1982) ▪ Gateway ASP C-1216 .......................................... (December 15, 2008) ▪ Hidden Valley ASP C-1028 .................................. (May 29, 2000) ▪ Kensington ASP C-1343 ...................................... (September 18, 2017) ▪ Meadow View ASP C-1290 .................................. (August 6, 2013) ▪ Mission Heights ASP C-858 ................................. (March 28, 1989) ▪ Mountview Industrial ASP .................................... (January 4, 2000) ▪ Northeast ASP C-1087 ........................................ (April 7, 2003) ▪ Northgate ASP C-807 .......................................... (January 14, 1985) ▪ Northridge ASP C-1013 ....................................... (August 16, 1999) ▪ Northwest ASP C-1106 ........................................ (August 11, 2003) ▪ Pinnacle Ridge ASP C-1082 ................................ (September 9, 2002) ▪ Southeast ASP C-1060 ........................................ (September 4, 2001) Sameng Inc.

2.5

Storm Drainage Master Plan 2018 Final Report (Revision 1)

▪ ▪ ▪ ▪

City of Grande Prairie

Southwest ASP C-1066 ....................................... (May 21, 2002) West Industrial ASP C-1329 ................................ (May 29, 2017) West Mountview Industrial ASP ........................... (January 2012) Westgate ASP C-1186 ......................................... (November 5, 2007)

2.10.5 Area Redevelopment Plan (ARP) ▪ College Park ARP C-1015 ................................... (September 13, 1999) ▪ Downtown Enhancement Plan ARP C-1130 ▪ Hillside ARP C-1370 ............................................ (September 25, 2017) ▪ South Avondale ARP C-1202 ............................... (June 6, 2008) ▪ Swanavon ARP C-990 ......................................... (September 15, 1997) ▪ VLA / Montrose ARP C-1228 ............................... (August 10, 2009) 2.10.6 Outline Plan (OP) ▪ Airport Industrial OP C-1322 ................................ (May 29, 2017) ▪ Albinati Industrial Park OP-01-01 ......................... (March 19, 2001) ▪ Arbour Hills 2 OP C-1281..................................... (April 29, 2013) ▪ Canfor Lands OP-01-02 ....................................... (June 4, 2001) ▪ Centre West Business Park OP ........................... (October 7, 2002) ▪ Cobblestone OP-03-03 ........................................ (July 14, 2003) ▪ Cobblestone East OP-06-02 ................................ (March 26, 2007) ▪ Copperwood OP-06-06 ........................................ (May 22, 2007) ▪ Countryside North OP-05-04 ................................ (May 24, 2005) ▪ Countryside South OP ......................................... (September 4, 2001) ▪ Crystal Landing OP .............................................. (July 20, 2005) ▪ Fairway Developments OP .................................. (April 6, 2009) ▪ Fieldbrook OP C-1262 ......................................... (February 6, 2012) ▪ Flyingshot Lake OP.............................................. (June 26, 2000) ▪ Kennedy OP ........................................................ (July 27, 2009) ▪ Kensington OP C-1344 ........................................ (September 18, 2017) ▪ Kingsgate Landing OP ......................................... (June 16, 2008) ▪ Northridge OP OP-06-03...................................... (July 17, 2006) ▪ O'Brien Lake OP .................................................. (June 16, 2003) ▪ O'Brien Lake West OP C-1279 ............................ (April 1, 2013) ▪ Pinnacle West OP ................................................ (June 20, 2005) ▪ Railside Business Park OP .................................. (September 25, 2017) ▪ Resources Road OP ............................................ (June 11, 2001) ▪ Riverstone OP ..................................................... (August 14, 2006) ▪ Royal Oaks North OP .......................................... (May 7, 2007) ▪ Signature Falls OP ............................................... (February 27, 2006) ▪ Southeast Richmond Industrial (Hazco) OP ......... (July 15, 2002) Sameng Inc.

2.6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪

City of Grande Prairie

Stone Ridge OP ................................................... (June 16, 2008) Summerside OP .................................................. (October 11, 2005) Summerside East OP .......................................... (September 8, 2008) Trader Ridge OP C-1307 ..................................... (October 6, 2014) Vision West Business Park OP C-1353................ (May 15, 2017) West Carriage Lane OP ....................................... (January 26, 2009) West Terra OP C-1333 ........................................ (May 30, 2016) Westgate East OP C-1373 ................................... (March 12, 2018) Westgate West OP .............................................. (June 16, 2008) Drainage System Data

• Sewer pipe layout and information in AutoCAD format and in shape file / GIS format. • Stormwater Management Facilities Information (i.e. drawings, photos, information sheets). • Computer Models (XPSMWW) named as follows: 68Ave, CrLand, Gp01, Gp02, Gp04, Gp07, Gp08, Gp11, Gp15, Gp22, Gp24, Gp29, Gp30, Gp32, Gp35, Gp36, Gp37, Gp42, GpNE, GpNW, GpSE, NEDBS, Obrien, Pinnacle. • Additional information request for select sewer locations provided by City of Grande Prairie. Rainfall and Flow Monitoring Data • City of Grande Prairie rainfall data from 2012 to 2017, including installation reports. • City of Grande Prairie storm sewer flow monitoring data from 2009 to 2017, including installation reports. Historical Flood Records • Historical flood reports were not provided by the City. However, an Internet search and review of previous studies revealed that there is a recent history of flooding in the City; including most recently significant flooding caused by an intense rainfall event on August 2, 2016. More information is provided in Section 5.3. • It is recommended that the City compiles information such as news reports, pictures and videos (e.g. social media) of historical flood events for purposes of identifying flood prone areas and the extent of flooding. It is also recommended for the City to measure water level in ponds, especially ponds that are identified as being at a higher risk of flooding, during the most extreme events. This information can be used for future studies to help identify improvements and to prioritize them. This information is also useful to calibrate/validate the model results.

Sameng Inc.

2.7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Other Collected Data • City of Grande Prairie - Design Manual 2018 • City of Grande Prairie – Construction Manual 2018 • Various AutoCAD / Shape files, including cadastral • Recent LiDAR topographical data (dated May 2014 within the City of Grande Prairie) • Recent aerial photos (dated 2016) Coordinate System The City of Grande Prairie currently uses the 10TM coordinate system for all their database information. Nowadays, the 10TM system is quite obsolete. The Alberta Survey Control Monuments (ASCM) do not provide their coordinates in 10TM. It is also quite challenging to convert a 10TM drawing into other coordinate system as the conversion factors are complex. It is strongly recommended that the City uses the UTM coordinate system which is more widespread and used in the Province of Alberta. There is no difference in elevation between the two coordinate systems; the changes are purely with the X and Y coordinates.

Sameng Inc.

2.8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

3.0

City of Grande Prairie

Review of Municipal Development Standards Overview

This section presents a review of the City’s Storm Drainage System design standards as found in Section 12 of the City of Grande Prairie’s Design Manual 2018. The drainage design standards are summarized in Table 3-1. The City’s design standards were compared to the current standards for the City of Edmonton (Volume 3 Drainage, March 2015) and Strathcona County (December 2011); this comparison is included in Table 3-1. Additionally, the information available in the “Province’s Standards and Guidelines for Municipal Waterworks, Wastewater and Storm Drainage Systems - Part 5: Stormwater Management Guidelines (2013 and 1999)” is also included in Table 3-1. Recommended Changes to Current Design Standards 3.2.1

Section 1. - General

The design standards should indicate that the pre-development flow for raw land could also be determined based on a watershed study. 3.2.2

Section 2.1 - Composition and Control

As stated in the note of Table 12.2 of the design standards, “When using the Rational Method, pipe runs downstream of stormwater management facilities are to be upsized by 25% (of flow area) to allow for increased emergency drawdown capacity, some piped emergency overflow, and to allow for catchment boundary revisions at the time of detailed design.” This comment should not only apply to pipes designed with the Rational Method, but also to pipes designed using a model. A modified version of this comment should be included in Section 2.1. The note should then be deleted from Table 12.2 to eliminate redundancy. Modify the last paragraph to: “Detention facilities shall be designed as part of both the minor and major drainage systems. They must control the peak runoff conditions for events up to and including the 1-in-100- year return period.” 3.2.3

Section 2.2 – Rainfall Intensity-Duration-Frequency

A comprehensive review of the City’s IDF curves was completed and is presented in a memo entitled “Design Rainfall Assessment Memo” included in Appendix A. The following summarized the memo and the recommendations. • The current City of Grande Prairie IDF curves (Figure 3-1) were derived from the IDF curves developed by Environment Canada for the Grande Prairie Regional Airport. These curves used rainfall data collected between 1968 and 1993. The current IDF

Sameng Inc.

3.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

curves have a discontinuity at the 2 hours duration because two equations were developed for each return period. • Through analysis of rainfall data from many stations located near the City of Grande Prairie, new IDF curves were developed (Figure 3-2). The new IDF curves generally have larger intensities (10 to 60% more) than the current IDF curves for the smaller durations (less than 2 hours). For durations larger than 2 hours, the new IDF curves are similar to the current curves. These new curves are more in line with those of the City of Edmonton and Strathcona County. • The design standards should be updated to include the new IDF curves presented in the memo. • The tabulated version of the new IDF curves should be included as an appendix to Section 12 of the design standards (included in the memo).

Sameng Inc.

3.2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie Current IDF 100-yr Current IDF 50-yr Current IDF 25-yr Current IDF 10-yr Current IDF 5-yr Current IDF 2-yr

Rainfall Intensity (mm/hr)

100

1 1

100

1000

Rainfall Duration (minutes)

Figure 3-1: Current City of Grande Prairie IDF Curves

Figure 3-2: Proposed Updates to City of Grande Prairie IDF Curves

Sameng Inc.

3.3

Storm Drainage Master Plan 2018 Final Report (Revision 1)

3.2.4

City of Grande Prairie

Section 2.3 - Storm Catchment Calculations

Computer Modeling Requirements The current standard allows the option of using Rational Method for design of storm sewer systems for areas less than 65 hectares. With advances in computer modeling technology and the many shortfalls of the Rational Method, the City should mandate that the drainage design for all new developments (and drainage upgrade projects) be completed using a wellknown computer modeling software, regardless of the area being developed. The use of the Rational Method should only be allowed under circumstances where a computer model is not practical, or to validate the computer modeling results. The City should require models to integrate both the minor drainage system (i.e. storm sewers) and major drainage system (i.e. surface flows) to properly evaluate the system performance under surcharged conditions (i.e. larger than 5-year rainfall event). Modeling Software If the City wishes to indicate Innovyze’s XPSWMM as a preferred modeling software, they should also consider including other reputable software to that list, such as DHI Mike Urban and CHI PCSWMM. Time of Concentration – Inlet Time The minimum time of concentration (Tc) to be used for the Rational Method is currently stated as 15 minutes for large parklands, and 10 minutes for all other lands. The design standards should not indicate the minimum time of concentration, but it should rather indicate the “maximum overland time to the storm sewer inlet (Inlet Time)”. The maximum inlet time are recommended as follows: • 10 minutes for catchments 8 ha and larger with imperviousness of less than 50%. • 8 minutes for catchments smaller than 8 ha with imperviousness of less than 50%. • 7 minutes for catchments 8 ha and larger with imperviousness of 50% or more. • 5 minutes for catchments smaller than 8 ha with imperviousness of 50% or more. Synthetic Design Rainfalls A comprehensive review of the City’s synthetic design rainfalls was completed and is presented in a memo entitled “Design Rainfall Assessment Memo” included in Appendix A. The following summarized the memo and the recommendations. • The City of Grande Prairie uses three different synthetic design rainfalls for drainage design purposes: The 4-hour Chicago Distribution, the 12-hour AES distribution and the 24-hour SCS design storms. • The current synthetic design rainfalls underestimate the total precipitation when compared to the IDF curves. They should match.

Sameng Inc.

3.4

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

• The 2012 Drainage Master Plan suggested that the design 4-hour Chicago distribution rainfall event be modified to average the peak rainfall intensity over a 10 minutes duration instead of 5 minutes. The current design standards reflects that recommendation. We recommend restoring the peak rainfall intensity over a 5 minutes duration, as it more realistic and conservative. • It is recommended that the City uses the following synthetic design rainfalls for design of the drainage system (these recommendations purposely differ from the memo): ▪ The new 4-hour Chicago distribution as shown in Figure 3-3 is recommended. This design rainfall often guides the design of sewer pipes, given its very intense peak rainfall. ▪ The 12-hour Huff Distribution (1st quartile), the 24-hour Huff Distribution (1st quartile) and the 24-hour Chicago distribution as shown in Figure 3-4, should be used to size storm ponds. The Chicago distribution is likely the rainfall that will govern pond sizes, but the Huff-distribution should be evaluated nonetheless. • It is recommended that the City removes the 24-hour SCS distribution from their design standards. This rainfall distribution is extremely intense and overconservative (even more so than the Chicago distribution). The SCS method is not commonly used by municipalities and are being abandoned by most of the U.S. as they are not representative of actual rainfalls. The 24-hour Chicago distribution, which is derived from the City’s IDF curves, is more suitable. • It is also recommended that the City removes the 12-hour AES distribution from their design standards. It is not a well-documented rainfall distribution, and we are not aware of another Alberta municipality using it. It shall be replaced with the 12- and 24Huff Distribution. • The tabulated version of the four new/updated design rainfalls should be included as an appendix to Section 12 of the design standards (included in the memo).

Sameng Inc.

3.5

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie 180

100

New 4-hour Chicago 100-yr

Current 4-hour Chicago 100-yr

Current 4-hour Chicago 10-yr

New 4-hour Chicago 25-y r New 4-hour Chicago 10-y r

140

Rainfall Intensity (mm/hr)

Current 4-hour Chicago 5-y r

Rainfall Intensity (mm/hr)

New 4-hour Chicago 50-y r

160

Current 4-hour Chicago 25-yr

70 60 50 40 30

New 4-hour Chicago 5-yr

New 4-hour Chicago 2-yr

120 100 80 60 40

0 0

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240

Rainfall Duration (minutes)

Figure 3-3: Current (left) and New (right) City of Grande Prairie 4-Hour Chicago Distribution Design Rainfalls

80 New 24-hour Chicago 100-yr New 24-hour Chicago 50-yr

New 24-hour Chicago 25-yr

New 24-hour Chicago 10-yr New 24-hour Chicago 5-y r

Rainfall Intensity (mm/hr)

New 24-hour Chicago 2-y r

50 40 30 20 10 0 0

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rainfall Duration (hours) 14

New 24-hour Huff 100-y r

New 12-hour Huff (1st quart ile) 100-y r

New 24-hour Huff 50-yr

New 12-hour Huff (1st quart ile) 50-yr

New 12-hour Huff (1st quart ile) 25-yr

New 24-hour Huff 25-yr

New 24-hour Huff 10-yr

New 12-hour Huff (1st quart ile) 10-yr

New 24-hour Huff 5-yr

Rainfall Intensity (mm/hr)

New 12-hour Huff (1st quart ile) 5-yr New 12-hour Huff (1st quart ile) 2-yr

New 24-hour Huff 2-yr

5 2

0 0

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rainfall Duration (hours)

Figure 3-4: New City of Grande Prairie 24-Hour Chicago (top), 12-Hour Huff (left) and 24-Hour Huff (right) Distribution Design Rainfalls

Sameng Inc.

3.6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

3.2.5

City of Grande Prairie

Section 2.6 – Manning’s Formula “N” Value

This section title is incorrectly labeled as “Valve” in the design standards. 3.2.6

Section 2.12 – Manhole Detail and Location

The current standard indicates a maximum spacing of 120 metres between manholes, with 90m for curved sewer. Some other municipalities have a minimum spacing of 150m, with some municipalities allowing even greater distances for larger diameter pipes. It is recommended that the City of Grande Prairie adopts the following spacing requirement: -

120m for pipes smaller than or equal to 375mm;

150m for pipes larger than 375mm, but smaller than or equal to 1200mm;

300m for pipes larger than 1200mm.

The City should discuss with their maintenance and operations staff prior to making this change. Increasing the manhole spacing may impact maintenance and cleaning. 3.2.7

Section 3.4 – Inlet / Outlet Control Devices

A critical component of a SWMF is the outlet control structure that regulates the water level and maintains the permanent pool. The current standards only indicated orifice plates and hydrobrakes with by-pass system as outlet control devices, but it is not specific about the design of the control structure itself. It is recommended that outflow control structures design standards / guidelines be included as a sub-section of the Design Standards to reflect the requirement of drawdown time, release rate, etc. Design of the outlet structure should allow for operational flexibility and to mitigate the risk of blockage from debris and/or freezing. It should also be possible to increase or decrease the rate of flow without physically altering the outlet structure (e.g. removable orifice plates). The outlet structure should include a slide gate or similar mechanism to isolate discharge out of the facility. The outlet works should include a bypass that allows rapid drawdown of the facility. This bypass should be designed to allow wet facilities to be drained below normal water level. The discharge rate from the bypass should be designed to the full capacity of the downstream system. Outlet control for ponds should be designed to hold the range of discharge rate such that the peak allowable discharge rate is not exceeded, and that drawdown times are quick enough to account for potential subsequent events. From design full level, facilities should draw down volume equivalent to runoff from a 1 in 5year storm event within 24 hours, and they should draw down 90% of their live storage within 96 hours (4 days).

Sameng Inc.

3.7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

The designer should include an operation and maintenance manual as part of the outlet control structure as-built submission. 3.2.8

Section 4.3 â&#x20AC;&#x201C; Engineering Drawing Requirements

The 2012 Storm Drainage Master Plan recommended including pond bottom elevation and freeboard volume for stormwater management facility (SWMF) drawings. The current standards added the pond bottom elevation in their requirement, but not the freeboard volume. It is recommended that the freeboard storage volume be included on the drawings. Additionally, we recommend that the depth-storage curve and the depth-area curve (and tables) be included on the SWMF drawing submissions. 3.2.9

Section 4.4 â&#x20AC;&#x201C; Design Details for Wet Ponds

In Section 4.4.9 - Inlet and Outlet requirements, the City should add the requirements for providing an emergency overflow system for ponds in new development areas. For pond design in existing and infill areas without an adequate overflow provision, a minimum freeboard of 0.3m above high water level is recommended. 3.2.10 Section 4.5 â&#x20AC;&#x201C; Design Details for Constructed Wetlands Constructed wetlands should be designed around naturally low topography and features, and they should avoid disruption of natural wetland habitats as much as possible. The goal of constructed wetlands is to add to and utilize the storage and water quality improvements provided by natural wetlands, without negatively impacting them. A wetland specialist should be consulted through the design of the facility and its tributary development to ensure that the water level and water fluctuations will not negatively impact the wetland. Both normal water levels and water fluctuation patterns should be kept as close to natural as possible, unless recommended otherwise by a wetland specialist. The standard indicates that wetland surface area is typically 3% to 5% of the drainage area. While 3% may be considered the lower bound for wetland areas, there is no established upper bound. Wetlands should occupy as much land as necessary to meet other criteria such as water retention volumes, habitat, connectivity, etc.

Sameng Inc.

3.8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

3.2.11 Section 4.6 – Design Details for Dry Ponds The Dry Pond Concept drawing of the City’s 2018 Design and Construction Manual (Figure 12.3) reflects a maximum ponding depth in dry ponds of 2.0m, but the text of Section 4.6.3 reflects the old limit of 1.5m. Furthermore, this text and corresponding figure assume that the outlet pipe is at the same elevation as the pond bottom, but in some instances, the outlet pipe may be installed lower than the pond bottom. The text should be corrected to: “The maximum HWL live storage depth in a dry pond is 2.0 m measured from the invert elevation of the outlet pipe or measured from the pond bottom elevation at the outlet pipe, whichever is smaller. Refer to Figure 12.3.” 3.2.12 Section 4.7 – Design Details for Drainage Parkways Drainage parkways should be designed around the natural topography of the area and should avoid altering the boundaries and function of Environmentally Sensitive Areas as much as possible. The maximum flow/ponding depth is stated as 1.0 m from NWL (Section 4.7.2). It is recommended for this depth to be modified. Drainage parkways should have two specified design water levels, with appropriate setbacks: a frequently flooded level (max 0.5m above NWL for a 1:5-year event); and an infrequently flooded level (max 1.5m above NWL for 1:100-year event) Where drainage parkways discharge to wetlands, the end of the parkway should be designed as a forebay. Section 4.7.7 references inlet and outlet structures for dry ponds. Inlet/Outlet structures for drainage parkways should typically be submerged (under the NWL) and should be designed to resist blockages from debris and vegetation. A maximum bar spacing of 100mm is also recommended. Additional Recommendations to Design Standards 3.3.1

Water Quality Control Facility Design and Monitoring

Water quality control is a vital component in the design process of the drainage system. As we are utilizing more linear water drainage corridors and incorporating Environmentally Significant Areas (ESAs) into the future development plans, the water quality control facilities should be considered as an essential element when designing drainage systems. It is suggested to add a section specifically discussing the design criterion of the water quality control facilities. Sediment removal, oil and grease separation, and other water quality indexes should be considered and quantified. Design and monitoring requirements should be based on recommendations from watershed studies, as discussed in Section 10 of this report. Sameng Inc.

3.9

Storm Drainage Master Plan 2018 Final Report (Revision 1)

3.3.2

City of Grande Prairie

Lot-Level Best Management Practices

Guidelines from Alberta Environment encourages municipalities to promote lot-level best practices for managing runoff. These practices are to reduce the impact of development on runoff rates, prevent pollution of waterways, and manage groundwater levels in urban areas. Current best practices are summarized below. These should be included in the design standards. •

Reduced Lot Grading – is intended to reduce runoff volumes and increase travel times. Outside of building envelopes, relatively flat lots will drain more slowly, allowing more runoff to soak into the ground, and reducing the potential travel distance of surface contamination. In flat areas, lot grading of less than 2% should be considered.

•

Surface Ponding and Rooftop Storage – flat rooftops may be used to store direct runoff, which would reduce the load on stormwater infrastructure. Surface ponding in parking lots and green spaces may also be used to reduce peak flow rates. When these practices are used in private lots, there must be some way to ensure they are maintained in subsequent improvements.

•

On-Lot Infiltration Systems – infiltration systems may be used to drain small areas without connection to a minor drainage system. Infiltration systems drain primarily through groundwater recharge, and so are limited to places where the risk of contamination is small, and the groundwater table allows for adequate infiltration.

Sameng Inc.

3.10

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

City of Edmonton December 2014 Design and Construction Standards Volume 3

Storm sewers shall be designed as a separate system and consider both minor and major drainage

Storm sewers shall be designed as a separate system

1. GENERAL Storm and Sanitary systems

Predevelopment flow

Strathcona County December 2011 Design Standards Section 4.4

Storm sewers shall be designed as a separate sewer system

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Storm sewers shall be designed as a separate sewer system Assess the need for discharge controls to meet downstream hydrologic constraints identified in the watershed drainage plan

Based on watershed study

5 L/s/ha

Upsize pipe by 25% downstream of SWMFs.

1 in 5 year, where required 1 in 10 year for high value commercial areas

1 in 5 year for area â&#x2030;¤ 30 ha, 1 in 5 year + 25% for area > 30ha,

1 in 5 year or greater

1 in 100 year

1 in 100 year and historic storm events

1 in 100 year

2.MINOR SYSTEM 2.1 COMPOSITION AND CONTROL Return Period - Minor System

5 Year 54.1 43.4 28.0 17.1 10.1 5.9 3.7 2.3

| | | | | | | | |

100 Year 95.7 76.0 48.3 29.2 17.1 9.9 6.7 4.3

5 Year 65.2 53.2 35.6 22.6 13.9 8.4 3.7 2.2

| 100 Year | 155.0 | 124.6 | 83.3 | 54.4 | 35.1 | 22.5 | 11.0 | 7.0

Table 3.1 - Page 1 of 16

5 Year 67.7 53.5 35.1 22.7 14.5 9.28 4.54 2.89

1 in 5 year for larger municipalities, 1 in 2 year for several communities faced with limited financial reserves

| | | | | | | | |

100 Year 128.7 101.4 66.2 42.5 27.1 17.2 8.36 5.29

5 Year 53

14.8

3.2 2.2

Table 3.1 Comparison of Storm Drainage Standards Parameter 2.3 STORM CATCHMENT CALCULATIONS Max Area for Rational Method

Minimum Runoff Coefficients

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

City of Edmonton December 2014 Design and Construction Standards Volume 3

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

< 65 ha

≤ 65 ha

< 65 ha

Recommend <50 ha

1:5 Year | 1:10 Year | 1:100 Year

Based on zoning and imperviousness. For return period: - ≤1:10 year, C = (0.95ximp)+0.1(1.0-imp); - >1:10 year and ≤1:25 year, 1.1C; - >1:25 year and ≤1:50 year, 1.2C; - >1:50 year, 1.25C to a max of 0.95

Residential

0.50 | 0.50 | 0.60

Apartments

0.70 | 0.70 | 0.80

Downtown Commercial Neighbourhood Commercial Light Industrial

0.85 | 0.90 | 0.90 0.70 | 0.70 | 0.80 0.60 | 0.70 | 0.70

Single Family - 0.65 Low rise - 0.65; Medium rise - 0.75; High rise - 0.9 0.90 0.90 0.6

Lawns, Parks, Playgrounds

0.20 | 0.25 | 0.30

Parks, Schools - 0.3

Undeveloped Land (Farmland) Paved Streets Gravel Streets Commercial Asphalt, Concrete, Roof

0.10 | 0.15 | 0.20 0.90 | 0.95 | 0.95 0.25 | 0.35 | 0.65

0.95 0.9 0.95

Multi Family

1:100 Year - Add 25% to a max of 0.95 Typical 1:5 Year coefficients

Single Family - 0.40

Single Family 0.30 - 0.50 0.50 - 0.70

Must be calculated Must be calculated Must be calculated

0.9 0.30 0.50

Medium Industrial, Industrial Business

0.90

Minimum Percent Impervious 50%

Multi-Family Residential

65%

Medium-Rise Apartment High-Rise Apartment Neighbourhood Commercial Downtown / Large Commercial Light Industrial Medium Industrial Heavy Industrial Public Park Predominantly Grassed Areas Schools Asphalt, Concrete, Roof

90% 80% 90% 70% 10% 10% 30% 100%

0.75 0.90 Typical Range 40% - 60% Row Housing/Multi Family/Low Rise Apt 40% 90% 40% - 90% 40% - 100% 40% - 100% 40% - 100% 50% - 100% 40% - 100% 40% - 70% 10% - 50% 10% - 30% 10% - 50% 90% - 100%

Table 3.1 - Page 2 of 16

0.70 - 0.95 0.50 - 0.70 0.50 - 0.80 0.15

Parks 0.10 - 0.25, Playgrounds 0.20 - 0.35 0.10 - 0.30 0.70 - 0.95

Row Housing/Multi Family/Low Rise Apt - 0.65

High Density Public Parks, Schools Heavy Industrial

Medium rise Apartment High rise Apartment Imperviousness Single Family Residential

1:100 Year - Increase to reflect the impact of antecedent moisture conditions

0.60 Must be calculated

Multi-Unit detached 50% Multi-Unit attached 70% Apartments 70% 70% 95% 80% 90% Parks 7%, Playgrounds 13% Lawns 0% 0.5 Roofs 90%, Paved streets 100%

Table 3.1 Comparison of Storm Drainage Standards Parameter

Minimum Time of Concentration Computer Modeling Requirements

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

Should be Maximum Inlet Time Varies depending on 15 Minutes for large parklands imperviousness (see report) - 5 10 Minutes for all other lands to 10 minutes. Required for all projects Required where area â&#x2030;Ľ 65 ha

Model

Integrated surface/pipe model preferred. Other reputable software XP-SWMM preferred should be added to acceptable model list (e.g. DHI Mike Urban, CHI PCSWMM)

Design Hyetograph (Synthetic Design Rainfall)

- 4 hour and 24 hour Chicago hyetographs, and 12-hour and 24-hout Huff Distribution (1st quartile) hyetographs

City of Edmonton December 2014 Design and Construction Standards Volume 3 Max 10.4 Minutes for catchments 40 ha and larger with imperviousness of 30%. Shorter inlet times for smaller areas and higher imperviousness Required where area > 65 ha

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Max 15 Minutes for residential areas, Shorter inlet times for commercial, industrial or high density residential areas required Required where area > 65 ha

Any as long as the engineer can demostrate that the model is appropriate and accurate as compared to commonly accepted models

DHI-Mike Urban (Mouse) and Mike 21 models are recommended

- 4 hour Chicago Hyetograph for mains, - 4 hour Chicago Hyetograph for conveyance, - 12 hour AES and 24 hour SCS for - 24 hour Huff hyetograph and historical storms detention ponds for stormwater management design

2.4 SITE DRAINAGE

Roof Drainage

- Residential, apartments, commercial and industrial buildings discharge to grassed or pervious areas. - Apartment buildings, commercial areas and industrial areas may discharge to the City's storm sewer system through an approved storm service connection

Weeping Tile connections

- Residential, apartments, commercial and industrial buildings shall discharge to grassed or pervious areas. - One and two family dwellings may discharge to the storm sewers system Foundation drain service connections are to be when a service connection has been provided to all new detached, semi- detached provided. and duplex residential units. - Apartment buildings, commercial and industrial areas may discharge to the storm sewers system through an approved service connection.

Where storm sewer service connections are not provided to each lot or downspouts are not to be connected to a storm service, provisions to carry and discharge roof drain flows away from the building foundation and to control erosion are required.

Table 3.1 - Page 3 of 16

- Roof leaders must discharge to a landscaped area wherever possible. - Commercial sites may be connected to a storm service if this is not practical.

-Roof leaders to discharge to surface ponding areas where possible. - Rooftop storage for commercial, industrial, and institutional buildings

- A sump pump discharge collection service must be provided to the property line of each single Where appropriate, discharge to an infiltration family lot or multi-family unit. system. - Roof leaders or any other stormwater source must not be connected to this system.

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

Service Connections

- Multi-family residential, commercial and industrial development - storm service stubs shall be provided to each lot. - One and two family lots - storm service stub shall be provided when the seasonally corrected ground water level is within 3.5m of the road centerline design grades

Service Connection Design Criteria

- Redevelopment Areas: Allowable Flow = Site Area/Upstream Catchment Area x Capacity of the System - New Development Areas: Allowable capacity will be determined using 1:5 year IDF curve and the appropriate runoff coefficient

Service Connection Installation

- Residential Lots: 150mm with a 150mm - 100mm reducer at the property/easement line. Shall have a plug in it and be insulated if less than 1.8 m cover. - Multi-Family Residential, Commercial and Industrial Lots: Services based on allowable capacity determined by downstream. Provide 1:100 year onsite detention with max allowable discharge of 5 l/s/ha. Minimum allowable orifice size is 50mm.

2.5 MINIMUM PIPE SLOPES / VELOCITIES Minimum Flow Velocity Max. flow velocity

- Required for commercial, institutional, industrial and multiple residential properties. -Foundation drain service connections to be provided. - Storm service connections to be provided when roof leaders discharge would drain from one lot to another or when dictated by geotechnical requirements.

Strathcona County December 2011 Design Standards Section 4.4

Straight | Curve 0.40%

250 mm dia

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Sump pump service discharge connections required

0.6 m/sec 0.6 m/sec 0.6 m/sec < 3 m/s - special provisions required to < 3 m/s - special provisions required to prevent prevent displacement by erosion or 3.0 m/sec displacement by erosion or shock impact

Minimum Slope 200 mm dia

City of Edmonton December 2014 Design and Construction Standards Volume 3

0.6 m/sec when flowing full < 3 m/s - special consideration shall be given to prevent scouring

Min Slopes increase 50% on all curves

Based on 0.60 m/s velocity for pipe flowing at least half full Consider increasing grade for curves

0.40 % (foundation drain sewer)

0.28 % (foundation drain sewer)

NA 0.194% 0.145% 0.114% 0.092%

300 mm dia 375 mm dia 450 mm dia 525 mm dia

0.22% 0.15% 0.12% 0.10%

| | | |

0.25% 0.18% 0.15% 0.13%

0.22% 0.15% 0.15% 0.15%

600 mm dia and larger

0.10%

0.10% | 0.10%

0.15%

Table 3.1 - Page 4 of 16

0.077% for 600 mm to 0.010% for 2820 mm

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

2.6 MANNING'S FORMULA''N'' value PVC pipe Smooth walled concrete pipe Corrugated steel pipe (unpaved) Corrugated steel pipe (invert paved) Corrugated Metal Pipe - All Paved Gravel lined channels Concrete or asphalt lined channels

City of Grand Prairie V2018 Design Manual Section 12 0.013 0.013

City of Edmonton December 2014 Design and Construction Standards Volume 3

Strathcona County December 2011 Design Standards Section 4.4

All smooth-wall pipe - 0.013 All smooth-wall pipe - 0.013 0.024 0.020 0.013

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

0.013 0.013

Natural streams and grassed channels Other Comments

Correct section title to Manning's Formula "N" Value

2.7 HYDRAULIC GRADELINE Match pipe obverts

Inlet sewer obvert shall not be lower than outlet Match pipe obverts sewer obvert.

Convey design flow when flowing full with HGL at the pipe crown. Crown elevations should match at manhole junctions.

Length to first catchbasin or catchbasin manhole

300 m - Paved lanes for grade > 1%, 200 m - Paved lanes for grades between 0.8% and 1%, 200 m - Local road with grade > 1%, 150 m - Local road with grades between 0.6% and 1%, 120 m - Collector/Arterial roadway, 120 m - PUL lot for grassed swale at grade ≥0.8% or <0.8% for older subdivisions due to adjacent development restrictions.

180 m - Lanes & Walkways, 150 m - Roadway gutters

150 m

300 m

After First Catch Basin

Not specified (assumed to be same as 180 m - Lanes & Walkways, for first catchbasin) 150 m - Roadway gutters

150 m

120 m

At Manholes 2.8 MAXIMUM SURFACE DRAINAGE

2.9 DRAINAGE INTERCEPTION Catch basin Capacities F33 F36 F38/F39 F51 K2

2.10 MINIMUM GUTTER GRADE

Continuous Slope | Sump Condition

Designer responsible for determination

0.6% Min. Road grade

Table 3.1 - Page 5 of 16

0.6% 0.7% - lanes 0.8% - curves with Radius ≤ 20 m

0.40% 0.60% - ≤ 20 m length, or short radius curve

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Edmonton December 2014 Design and Construction Standards Volume 3

City of Grand Prairie V2018 Design Manual Section 12

2.11 MAIN DETAIL AND LOCATION

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Minimum Size

300 mm in general, 200 mm - Residential lot service main with grade ≥ 0.4%

300 mm - Storm sewers 250 mm - Catchbasin leads 200 mm - Foundation drain sewer

Minimum Cover

1.8 m from finished surface grade to top of pipe

2.0 m for pipe < 610 mm, 1.5 m for pipe ≥ 610mm, 1.5 m to top of pipe when not achieved, provide adequate insulation

Minimum Horizontal Separation

From Water Mains 2.5 m centre/centre for pipes ≤ 300m 2.2 m from outside walls for pipes > 300mm

2.4 m centre/centre between parallel sewers, 250 mm between sewers in common trench

Minimum Vertical Separation

500 mm from water mains from outside walls 500 mm from sanitary sewers from outside walls

Pipe Class

Shall be determined to withstand subsequent superimposed loading

Standard Practice for Design and Installation available

Shall be based on loading conditions.

Pipe Bedding

Class B sand bedding - pipes having water tight joints Standard Practice for Design and Installation Class B crushed gravel bedding - CSP available pipes

Shall be based on loading conditions.

2.12 MANHOLE DETAIL AND LOCATION Safety platforms Bar ladder rungs

300 mm, 150 mm - Sump Pump collection system

2.5 m from water mains, 1.8 m from gas lines

> 5.0 m depth

Location

Upstream end of each line, changes in pipe size, grade, material and alignment; Not in driveways or on private property; Frames and covers are not to be located within a sidewalk.

At all changes in sewer size, grade or alignment and at all junctions; Within roadway ROW within the travel lanes or At all transitions in size, grade or direction, at cenre medians between the outside curb lines; junctions and the end of mains. No closer than 1.5 m from roadway curb face; Not within a sidewalk.

Minimum Invert drop

30 mm, 60 mm at change in direction, Consider minor losses - inlet pipe > 525 mm & bend > 45° or velocity > 1.5 m/s

For sewers ≤ 600 mm: 30 mm for deflections < 45°, 60 mm for deflections of 45° to 90°, Detailed analysis for large sewers, high velocities or complex/unusual junctions

12 mm, 50 mm at change in direction

120 m, 90m on curved sewer.

150 m - < 1200 mm, 500 m - 1200 mm to 1650 mm, 800 m - ≥ 1800 mm

150 m

Maximum spacing

Tee Riser

1.2 m to pipe crown

Normally water mains cross above sewers, 0.5 m from water main crown to sewer invert

> 6.5 m in depth Spaced at 400mm O.C.

120 m - ≤ 375 mm, 150 m - > 375 mm and ≤ 1200 mm 300m - > 1200 mm

300 mm

May be utilized on lines ≥900 mm, Must be bedded in concrete to the springline of the pipe

Table 3.1 - Page 6 of 16

Safety-drop type, spaced 300-400 mm

At the end of each line; At all changes in grade, size and alignment; At all intersections.

120 m - ≤ 375 mm, 150 m - 450 mm to 750 mm Greater spacing allowed fro > 750 mm

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

Weeping Tile connections

are to be extended 1.5 m past the last house service lead, with the exception of storm mains in cul-de-sacs where service leads may be connected directly to the end of the line manhole provided that the lead enters the manhole less than 0.60 m above the invert of the main.

Drops at manholes

≤ 1.0 m - ensure free outflow and low backwater conditions will exist in the downstream sewer, > 1.0 m - specifically designed drop manhole may be required

City of Edmonton December 2014 Design and Construction Standards Volume 3

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

< 600mm, 0.8 depth point of both sewers should be matched; ≥ 600mm, drop manhole should be used

2.13 CURVED SEWERS - Only to follow curved ROW; - Radius ≥ 90 m or manufacturer's minimum recommended radius, whichever is larger; - Manholes shall be located at the beginning and end of the curve; d) Manholes shall be located at intervals ≤90 m along the curve; - Parallel to property line; - Minimum grade 50% greater than the minimum grade required for straight runs.

Run parallel to curb or street centreline

2.14 CATCHBASIN LEAD DETAIL AND LOCATION Minimum size Minimum grade Maximum length Minimum cover Hydraulic gradient

300 mm 2.0% 30 m 1.20 m from the finished road surface to the top of pipe

250 mm, 300 mm for F51 CB 1.0% 30 m

250 mm 1.0% 30 m 2.0 m

1.5 m

Match the obvert of the senior pipe.

2.15 OUTFALL DETAIL AT CREEKS Obverts of outfall pipes

≥ 150 mm above the 1:5 year flood level in the receiving stream.

Inverts of outfall pipes

Above winter ice level or located to avoid damage from ice breakup

Drop structures and energy dissipaters

- Where necessary to prevent erosion - Hydraulic analysis required at all outfalls

Above 1:5 year flood level of receiving stream

Erosion control measures are to be provided at and downstream of the outfall to prevent Use where necessary to prevent erosion erosion in the downstream channel.

Table 3.1 - Page 7 of 16

Only allowed for pipes ≥ 1.0 m

250 mm

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

City of Edmonton December 2014 Design and Construction Standards Volume 3

Outfall exit velocity

≤ 1 m/s and may be further limited ≤ 1 m/s and may be further limited depending depending on site specific soil and flow on site specific soil and flow conditions conditions

Safety

Grate with vertical bars ≤150mm to prevent entry

- Lockable grate with vertical bars spaced ≤ 150 mm. - Guardrails or fences along headwalls and wingwalls.

Aesthetics

- Should be as safe and attractive as is reasonably possible. - Cosmetic treatment or concealment to be considered. - Concrete surface treatment recommended.

- Should be as safe and attractive as is reasonably possible. - Cosmetic treatment or concealment is to be considered. - Concrete surface treatment is recommended.

2.16 RURAL RUNOFF INLETS Access Gratings 3. MAJOR SYSTEM 3.1 COMPOSITION AND CONTROL

Require road right-of-way or public utility lot for access. Hydraulic capacity = 200% of design flow rate

Composition

- Street system - detention facilities - parkland and any other land required to convey 1:100 year runoff

Control

Detention facilities to control the peak run-off condition for events up to the 1:100 year return period.

3.2 RETURN PERIOD EVENT 3.3 ON-STREET STORAGE AND FLOW-ACROSS CONSIDERATIONS

1:100 year

Containment

- Within City property - No building inundated at ground line.

Overland Flow

- Maintain continuity of the overland flow routes between adjacent developments. - Show overland route and depth of ponding on lot grading plan.

Ponding Depth

< 350 mm - Local / Collector Roads < 150 mm - Arterial Roadways

Velocity / Flow Depth

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Grates shall be provided to restrict access

Require road right-of-way or public utility lot for access. Hydraulic capacity = 200% of design flow rate

100 years

Below lowest ground elevation at buildings on adjacent property.

Max depth of ponding is limited to 350 mm.

Velocity | Permissible Depth 0.5 m/s | 0.80 m 1.0 m/s | 0.32 m 2.0 m/s | 0.21 m 3.0 m/s | 0.09 m

< 0.30m @Local Roads < 0.50m @ low points Velocity - Permissible Depth 0.5 m/s - 0.80 m 1.0 m/s - 0.32 m 2.0 m/s - 0.21 m 3.0 m/s - 0.09 m

Table 3.1 - Page 8 of 16

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

3.4 INLET/OUTLET CONTROL DEVICES - Inlet control with different styles of catchbasin grates is recommended. - Should be designed with a minimum 100mm sump.

Inlet

Outlet

City of Edmonton December 2014 Design and Construction Standards Volume 3

- Release rates to be confirmed by - Include bypass for rapid detailed assessment of downstream drawdown and draining below system. NWL - Orifice plates or "hydrobrakes" to - Include slide gate or similar to control release rates. isolate control structure - Minimum orifice restriction: 50 mm. - 90% drawdown from full within - 100mm sump. 96 hours - Control structures must be accessible - Drawdown from full for 1 in 5by land when pond is at high water year runoff within 24 hours level.

- Discharge prescribed in Neighbourhood Design Report - Slide gate to stop discharge - Means to bypass control element for rapid discharge at maximum rate allowable by downstream system - Volume equivalent to 1 in 5 year storm runoff within 24 hours - Volume equivalent to 1 in 25 year storm event within 48 hours -90% of total storage volume above NWL within 96 hours.

4. STORMWATER MANAGEMENT FACILITY DESIGN 4.1 OVERVIEW Ownership Emergency Overflow 4.3 ENGINEERING DRAWING REQUIREMENTS

SWM Facility Drawing Requirements:

Area submerged by 1:100 year event and the freeboard shall be City property. Provide for storms > 1:100 year if possible

- Stage-Storage Volume and Stage-Area Curves and tables of values, - High Water Level (HWL) design event, - Elevations at Pond Bottom, NWL, 5 year, 25 - High Water Level (HWL) design year, 100 year & HWL, event, - Volume at NWL, 5 year, 25 year, 100 year, - Elevations of Normal Water Level HWL & freeboard level, (NWL), 1:5 year level & HWL, - Area at Bottom, NWL, 5 year, 25 year, 100 - Add freeboard storage volume - Volumes at NWL, 1:5 year level & year level, HWL & freeboard level, on the drawings. HWL - Freeboard elevation, - Add depth-storage curve and - Freeboard elevation, - Lowest allowable building opening for lots depth-area curve (and tables) - Pond Bottom elevation, abutting the pond, on SWMF drawing - Lowest allowable building opening for - Pond & forebay depth at NWL, 5 year, 25 submissions. lots abutting the pond, year, 100 year level & HWL level, - Contributing basin size in ha, - Length of shoreline at NWL, 5 year, 25 year, - Measurements to locate submerged 100 year & HWL, inlet(s), outlet(s) & sediment traps - Pond and forebay area in ha. at NWL, 5 Year, 25 Year, 100 Year Level and HWL, - Contributing basin size in ha, - Measurements to locate submerged inlet, outlets & sediment traps

Table 3.1 - Page 9 of 16

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

4.4 DESIGN DETAILS FOR WET PONDS

City of Edmonton December 2014 Design and Construction Standards Volume 3

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Land Dedication

- The area of land to freeboard will be designated as a “Public Utility Lot” (PUL), “Road Right-of-Way”, or as approved by Council. - This designation will also apply to all rights-of-way for access to and protection of inlets, outlets and flow control facilities, and maintenance access routes to the pond.

- Area at NWL to be designated PUL - Privately owned land flooded as per design at The land required shall be designated a PUL. HWL to carry easements

Open water counts toward Municipal Reserve

Minimum Size

2 ha at NWL

2 ha

Side Slopes

Depth from NWL to Bottom Fluctuation

Freeboard

Pond Bottom Material

2 ha at NWL

- Maximum 4:1 to 5:1 above active storage zone; - Maximum 5:1 to 7:1 interior in active storage zone; - Maximum 3:1 exterior.

7H:1V - HWL to 1.0 m below NWL, 3H:1V - 1.0 m below NWL to bottom

7H:1V - HWL to NWL, 5H:1V - NWL to 1.0 m below NWL 3H:1V - 1.0 m below NWL to bottom

2.0 m to 2.5 m ≤ 2.0 m in residential areas for 1:100 year storm

Min 2.5 m

Min 2.0 m, Max 3.0 m.

1.5 m (or otherwise approved by Alberta Env.)

Max active detention storage depth of 1.5 m

0.5 m

Minimum 1.0 m, Municipal Engineer may reduce if Pond Min 0.3 m surface >2 ha and Fluctuation <1.0 m during 1:100 year event. - Ground water table < NWL: Bottom and side slopes to be impervious material (permeability coeff ≈ 1x10-6 cm/s). - Ground water table ≥ NWL: Pond bottom may be pervious material as dictated by geotechnical considerations.

- Ground water table < NWL: Bottom and side slopes to be impervious material (permeability coeff ≈ 1x10-6 cm/s). Impervious material. - Ground water table ≥ NWL: Pond bottom may be pervious material as dictated by geotechnical considerations.

Table 3.1 - Page 10 of 16

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

City of Edmonton December 2014 Design and Construction Standards Volume 3

Strathcona County December 2011 Design Standards Section 4.4

Narrow/dead bay areas to be avoided. Locate inlets & outlets to maximize detention time and circulation

Stagnant/poorly circulated areas to be eliminated. Semi-annual turnover at average annual precipitation.

- Fully submerged, crown at least 1.0m below NWL - < 25 m of pipe flooded - Invert of inlet at first manhole upstream ≥ NWL - Obvert of inlet at first manhole upstream ≥ 1:5 year Elevation - Inlets & outlets separated to avoid short- circuiting

- Fully submerged, crown ≥ 1.0m below NWL - Pipe inverts ≥ 100 mm above lake bottom - Invert of inlet at first manhole ≥ NWL - Obvert of inlet at first manhole ≥ 1:5 year Elevation - Inlets & outlets separated to avoid shortcircuiting

- Submerged inlets preferred with minimum 1.0 m below NWL

Sediment Removal Provisions

- Requires sediment removal process during neighbourhood development - Sediment basins at all inlet locations

- Requires sediment removal process during neighbourhood development - Sediment basins at inlet locations

Wet Pond Edge Treatment

- Compatible with the adjacent land use Edge treatment required for an increase or - Required from 1.5 m below to 3.0 m decrease from NWL of 0.3 m horizontally above NWL

Landscaping Requirement

Include all proposed public lands comprising the pond and all easement areas on private property, including areas from the pond edge treatment to the limit of inundation when the pond is filled to the design high water level.

Best Management Practices

- Recommend length to width ratio of 3:1 to 5:1 - Provide a broad surface - Maximize the flow path between inlet and outlet - The ratio of flow path length to width from the inlet to the outlet should be at least 3:1 - If there are multiple inlets, the lengthto-width should be based on the average flow path length for all inlets

Circulation Requirements

Inlet and Outlet Requirements

- Add requirement for providing an emergency overflow system for ponds in new developments. - For pond design in existing and infill areas without an adequate overflow provision, a minimum freeboard of 0.3m above high water level is recommended.

Table 3.1 - Page 11 of 16

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

4.5 DESIGN DETAILS FOR CONSTRUCTED WETLAND

City of Edmonton December 2014 Design and Construction Standards Volume 3

- Add: Constructed wetlands should be designed around naturally low topography and features, and they should avoid disruption of natural wetland The area of land to freeboard will be habitats as much as possible. designated as a PUL, ROW or as The goal of constructed approved by Council wetlands is to add to and utilize the storage and water quality improvements provided by natural wetlands, without negatively impacting them.

The area of land to HWL will be designated as a PUL

Suspended Solids Removal

Minimum requirements for total suspended solids removal is 85% of particle size 75um or greater

Wetland Drainage Area

- Minimum drainage area of 5 ha, - Smallest practical drainage area - 20 ha, - Hydrological studies required, - City prefers fewer larger wetlands vs. series of small wetlands, - Sediment controls required during development in the drainage area

- Minimum drainage area - 5 ha, - Smallest practical drainage area - 20 ha, - Hydrological studies required, - City prefers fewer larger wetlands vs. series of small wetlands, - Sediment controls required during development in the drainage area

Wetland Soil Characteristics

- Deep water areas - low soil permeability 10-7 m/s recommended - Vegetative zones - can use recently displaced wetland soils, sterilized topsoil or peat from within drainage basin - 10 cm to 30 cm of soil in vegetative zone. - Planting be done over the 2 years following construction.

- Deep water areas - low soil permeability 10 -7 m/s recommended, - Vegetative zones - can use recently displaced wetland soils, sterilized topsoil or peat from within drainage basin - 10 cm to 30 cm of soil in vegetative zone. - Planting be done over the 2 years following construction.

Wetland Vegetation

Plant diverse species within one year after construction;

Upland Vegetation in the Extended Detention Storage Area around the Wetland

Minimum 2 m mow strip required from PUL boundary to NWL

Minimum 2 m mow strip required

Land Dedication

Table 3.1 - Page 12 of 16

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Considered for areas >5ha

transplant from local donor sites

Table 3.1 Comparison of Storm Drainage Standards Parameter

Wetland Water Depth

Wetland Surface Area

Wetland Volume

Length to Width Ratio

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12 - 0.1 m to 0.6 m, average 0.3 m - Deep water areas (> 2 m) < 25% of surface area, - Water fluctuations > 1 m above NWL should be infrequent

- Add: Wetlands should occupy as much land as necessary to - Minimum 1 ha at NWL, meet other criteria such as - typically 3% to 5% of drainage area water retention volumes, habitat, connectivity, etc. - 35% Impervious: 80 m3 dead storage/ha, - 85% Impervious: 140 m3 dead storage/ha Minimum of 3 for effective flow path at low flow

City of Edmonton December 2014 Design and Construction Standards Volume 3

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

0.1 m to 0.6 m, average 0.3 m Deep water areas (> 2 m) < 25% of surface area, Water fluctuations > 1 m should be infrequent

Average depth 0.3 m Approx. 10% of surface area 1.5 to 2.0 m deep sediment forebay Active storage 0.3 to 0.6 m

Minimum 1 ha, typically 3% to 5% of drainage area

Approx. 5% of watershed area

35% Impervious - 80 m3 dead storage/ha, 85% Impervious - 140 m3 dead storage/ha Minimum of 3 for effective flow path at low flow

Forebay

- Required at each major inlet (>10% total storm inflow) - 2.4 m to 3.0 m deep - Require maintenance access for sediment removal - 7H:1V Side slopes

Permanent Pool at the Outlet

- 2.4 m to 3.0 m depth, - 7H:1V max side slopes along accessible open and deep water

2.4 m to 3.0 m depth, 7H:1V max side slopes along accessible open and deep water

Inlet and Outlet

- Inlets are to discharge to a forebay, - Variable water level control required. Control structure capable of maintaining NWL ±0.5m, - Located to avoid short-circuiting, - Max depth 3.0 m, - Submerged, crown ≥1.0m below NWL, - Pipe inverts ≥100 mm above bottom, - Maintenance access to forebay & permanent pool, - Emergency overflow to overland route where possible

- Inlets are to discharge to a forebay, - Variable water level control required. Control structure capable of maintaining NWL ±0.5m, - Located to avoid short-circuiting, - Max depth 3.0 m, - Submerged, crown ≥1.0m below NWL, - Pipe inverts ≥100 mm above bottom, - Grassed maintenance access to forebay & permanent pool, min 4 m wide

Grading

- 5H:1V: or flatter side slopes, terraced slopes acceptable, - 2 m wide marsh bench with 10H:1V slope at NWL, - 7H:1V max side slopes along accessible deep areas, - 2 m wide mow strip, 7H:1V side slope at accessible deep water areas, 5H:1V in other areas

Table 3.1 - Page 13 of 16

As low as 1:1

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

City of Grand Prairie V2018 Design Manual Section 12

City of Edmonton December 2014 Design and Construction Standards Volume 3

Floatables, Oil and Grease

Inlets & outlets below NWL to trap floatable materials, oil and grease

Maintenance

Additional maintenance as identified in watershed study

- Developer required to provide operations and maintenance manual, - 2 Year maintenance & warranty period from Construction Completion Certificate (CCC), - Sediment removal from forebays required prior to Final Acceptance Certificate (FAC), - Sediment removal required when forebay & permanent pool volume reduced by 25%, - Inspection required twice/year during maintenance period. Inspection reports to be submitted when applying for FAC.

Additional monitoring as identified in watershed study

- Developer shall monitor stormwater quality, - Parameters: TSS, TP, NH3, BOD, faecal coliforms, - Developer shall monitor wetland & upland vegetation and take corrective action as required, - Vegetation survey to be submitted for FAC. 75% of grass cover and 30% of non grass emergent vegetation must be established

- Developer shall monitor stormwater quality, - Parameters: TSS, TP, NH3, BOD, faecal coliforms, - Developer shall monitor wetland & upland vegetation. Take corrective action as required, - Vegetation survey to be submitted for FAC. 75% of grass cover and 30% of non grass emergent vegetation must be established

Access

Required to all inlets & outlets

Fencing

- Developer to use natural solutions (grading, planting strategies) to provide safety features, - Developer to provide fence at PUL boundary with openings for maintenance and access to trails

Mosquito Control

Developer to include design features that minimize mosquitoes

Land Dedication for Dry Ponds

PUL, ROW or as approved by Council to freeboard

PUL to 5 year water level, PUL or private land covered by easement for 5 year to design HWL

Frequency of Operation

Dry ponds to be off-line, Dry ponds to be off-line, Require provisions to facilitate clean up Require provisions to facilitate clean up if if contain runoff for events < 1:2 year. contain runoff for events < 1:2 year.

Monitoring

4.6 DESIGN DETAILS FOR DRY PONDS

Table 3.1 - Page 14 of 16

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Table 3.1 Comparison of Storm Drainage Standards Parameter

Depth of Ponding

Recommended Changes (see report for details)

City of Edmonton December 2014 Design and Construction Standards Volume 3

City of Grand Prairie V2018 Design Manual Section 12

- Correct text to: “The maximum HWL live storage depth in a dry pond is 2.0 m measured from the invert elevation of the outlet pipe, or measured from the pond bottom elevation at the outlet pipe, whichever is smaller. Refer to Figure 12.3.” Max 1.5 m from invert of outlet pipe - The text and corresponding figure assume that the outlet pipe is at the same elevation as the pond bottom, but in some instances, the outlet pipe may be installed lower than the pond bottom.

Max 3.0 m from invert of outlet pipe

Dry Pond Bottom Grading and Drainage

Min 1%, greater where feasible, ≥ 2% for lateral slopes, French drains may be required

Min 0.7%, ≥ 1.0% where feasible, ≥ 1.0% for lateral slopes, French drains may be required Max 7H:1V within private property, Max 5H:1V within public property

Side Slopes

Max 5H:1V within public property

Landscaping

Landscaping plans to be submitted with Landscaping plans to be submitted with engineering drawings, engineering drawings, Min requirement - establish grass cover Min requirement - establish grass cover

Inlets and Outlets

- Require safety grate with Max clear spacing of 150 mm, - Grated outlet's hydraulic capacity ≥ 200% design flow, - Flow velocity ≤ 1.0 m/s, - Fencing/guardrails for headwalls & wingwalls, - Inlet & outlet to be separated, - Emergency overflow to overland route where possible

Best Management Practices for Dry Ponds

- Shape pond to minimize short circuiting, - Minimize turbulence in main treatment area, -Consider methods to reduce scour of pond bottom

- Require safety grate with Max clear spacing of 150 mm, - Grate outlet's hydraulic capacity ≥ 200% design flow, - Flow velocity ≤ 1.0 m/s, - Fencing/guardrails for headwalls & wingwalls, - Inlet & outlet to be separated

Table 3.1 - Page 15 of 16

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Typically 1.0 to 1.5m; 0.6m freeboard

1% minimum 4H:1V

Table 3.1 Comparison of Storm Drainage Standards Parameter

Recommended Changes (see report for details)

4.7 DESIGN DETAIL FOR DRAINAGE PARKWAYS Land Dedication for Drainage Parkways Depth of Ponding

Max 0.5m for events <1:25 year. Max 1.5m for events up to 1:100 year

City of Grand Prairie V2018 Design Manual Section 12 PUL, ROW or as approved by Council to freeboard Max 1.0 m measured from the NWL

Base Width and Slope

5.0 m Min base width, with low flow channel 0.5% Min longitudinal slope, 1.0% preferred

Side Slopes

Max 5H:1V

Access

Min 5 m setback on one side for walkways/access

Landscaping

Landscaping plans to be submitted with engineering drawings, Min requirement - establish grass cover

Inlets and Outlets

City of Edmonton December 2014 Design and Construction Standards Volume 3

- Require safety grate with Max clear spacing of 150 mm, - Inlets and Outlets should be - Grated outlet's hydraulic capacity submerged (under the NWL), â&#x2030;Ľ200% design flow, and include self-clearing grates - Flow velocity â&#x2030;¤1.0 m/s, to prevent blockages. - Fencing/guardrails for headwalls & - Maximum clear spacing for wingwalls, safety grate shall be reduced to - Inlet & outlet to be separated, 100mm. - Emergency overflow to overland route where possible

4.8 RECEIVING WATERS - Measures to prevent any increase of downstream erosion. - Construct appropriate measures downstream in case of erosion -Consider preservation of watercourse aesthetics and wildlife habitat 4.9 CULVERTS AND BRIDGES - Consider backwater effects over a range of flows - Design requires assessment for both nominal flow and the flow during 1:100 year event.

Table 3.1 - Page 16 of 16

Strathcona County December 2011 Design Standards Section 4.4

Alberta Evironment and Parks March 2013 and 1999 Standards and Guidelines

Storm Drainage Master Plan 2018 Final Report (Revision 1)

4.0

City of Grande Prairie

Existing Drainage System Overview

This section provides a summary of the current drainage infrastructure in the City of Grande Prairie, including an overview of the topography and drainage basins. Topography The overall topography and major drainage basins near the City of Grande Prairie is illustrated in Figure 4-4 (city area) and Figure 4-5 (around city). Elevations in the City range from about 625m Above Mean Sea Level (AMSL) at the southeast of the City (in Bear Creek) to 698m AMSL to the north and up to 713m AMSL to the west. About 95% of the developed areas of the City is situated within the 650m to 685m elevation range. The highest developed areas of the City are to the northeast (i.e. Albinati Industrial, Crystal Ridge, Northgate, Lakeland, Crystal Lake Estates, Mountview) with elevations typically ranging between 675m and 690m. The Central Business District is at an elevation of 655m to 665m. Major Drainage Basins and Drainage Features 4.3.1

Overview

Runoff from the City of Grande Prairie discharges to many receiving waterbodies and watercourses. The main City drainage basins – delineated based on topography alone, not based on the sewer system (although they are very similar) – are shown in Figure 4-4 and Figure 4-5. The major drainage basins are summarized as follows and explained in more details in the next sub-sections: • Most of the City drains directly into Bear Creek, especially the northwest part of the City and areas that are adjacent to the Creek. The Grande Prairie Reservoir is located at the heart of the City along Bear Creek. Bear Creek flows in a southeast direction and outlets into Wapiti River southeast of the City boundary. • To the northwest, a small part of the City (currently undeveloped) drains into Bear Lake. Bear Lake is at the upstream end of Bear Creek and collects drainage from a large area northwest of the City. • To the west, a small area (currently undeveloped) drains into Hughes Lake. Hughes Lake overflows to the east and into Bear Creek. • To the west and southwest, runoff from mostly undeveloped areas drains into Hermit Lake and Flyingshot Lake which eventually flows southeast and into Bear Creek at the south end of the City. • To the northeast, a small and mostly developed area drains into Crystal Lake. Crystal Lake does not have a natural outlet, but a sewer pipe conveys any excess water volume from Crystal Lake to a ditch northeast of the City along the south side of Sameng Inc.

4.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Secondary Highway 670. The overflow from the lake into that pipe happens at an elevation of 681.79m. Natural overflow of Crystal Lake to the northeast and through the residential area (127 Avenue) would happen at an elevation of about 682.17m. • At the northeast corner of the City, drainage from a mostly undeveloped area is southeast into a small unnamed well-defined watercourse that outlets into Bear Creek about 7km straight east of the City. • Also to the northeast of the City, a very small area drains north and into the Clairmont Lake watershed. Clairmont Lake’s outlet is west into Grande Prairie Creek. • To the southeast, drainage from developed and soon-to-be-developed lands is into the Woody Channel which outlets into Bear Creek about 500 metres southeast of the City limits. • To the east, a small mostly undeveloped part of the City drains into Wood Lake. Wood Lake overflows east and eventually into Bear Creek. 4.3.2

Bear Creek

Bear Creek (also named Bear River) is a south-flowing watercourse that bisects the City along its center. It is the primary receiving watercourse for the City of Grande Prairie, with all the City runoff eventually discharging to Bear Creek. Bear Creek starts nearly 50 km upstream (northwest) of Bear Lake. It enters the City to the northwest at an elevation of approximately 662m. It conveys drainage from a large drainage area northwest of the City (about 1,470 km2 at the City limits), including Bear Lake (Bear Lake Watershed) and Grande Prairie Creek (Grande Prairie Creek Watershed). The Creek crosses many major roads in the City including (from upstream to downstream): Township Road 722, 116 Street, Township Road 720 (132 Avenue), Highway 43 (108 Street/116 Avenue), 99/100 Avenue, a railroad track just south of 99 Avenue, 84 Avenue, 68 Avenue, and Resources Road (just outside City limits). Many pedestrian bridges also cross the Creek. Bear Creek exits the City limits to the south at an elevation of 624m and with a total drainage area of 1,635 km2. It discharges into the Wapiti River approximately 18km southeast of the City boundary. The Creek collects a total drainage basin of 1,910 km² at the confluence with Wapiti River. The Wapiti River flows in a northeast direction and flows into the Smoky River only 16km downstream (east) of the confluence with Bear Creek. Smoky River flows northeast into the Peace River at Peace River, AB. The Peace River flows northeast and discharges into Great Slave Lake, NWT. The Great Slave Lake empties through the northwest-flowing Mackenzie River and into the Arctic Ocean via the Mackenzie Delta near Inuvik, NWT. Bear Creek has been well studied in the past. A flood risk mapping study of the Creek within the old City limits was completed in 2007, and another study was completed in 2017 to

Sameng Inc.

4.2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

include recently annexed areas northwest of the City. A slope stability and erosion assessment were also completed in August 2011. See Section 2.3 for a summary of these studies. 4.3.3

Grande Prairie Reservoir

The Grande Prairie Reservoir, covering about 0.14 km2, is located along the Bear Creek south of 108 Avenue and east of 108 Street. It is controlled by the Bear River Control Structure, a dam built in 1948 and reconstructed in 1975-76. Releases from the reservoir are controlled by a spillway with 2 radial gates each 5 m wide. Water level in the reservoir varies from 650.40 m in the winter to 652.58 m in the summer. The top of the dam is estimated to be around 655 m. Bear Creek just downstream of the structure has an elevation of 644.73m, resulting in a drop of about 5.7m to 10.3m from the reservoir to Bear Creek, depending on the reservoir water level. A Reservoir Feasibility Study, which provides a comprehensive review of the reservoir and associated structures, was completed in 2012. See Section 2.3 for a summary of this study. 4.3.4

Bear Lake

Bear Lake, covering about 31 km2, is the largest lake in the Grande Prairie area. It is located just northwest of the City boundary. Bear Lake collects drainage from a mostly agricultural area northwest of the Lake, as well as runoff from the Saddle Hills area (forest). The Bear Lake Watershed area is estimated at 1,130 km2. With a normal water level of about 663m AMSL, Bear Lake discharges into Bear Creek via its only outlet at the east end of the lake. Because of its size, Bear Lake buffers flows from the upstream drainage areas into Bear Creek. 4.3.5

Hughes Lake and Downstream Conveyance

Hughes Lake is located entirely within City limits to the northwest. It has a surface area of 0.43km2 and a drainage basin area of about 3.8 km2. Its water surface elevation is about 666.2m AMSL. The lakeâ&#x20AC;&#x2122;s natural outlet is to the southeast at an elevation of 667.8m and into the adjacent wetland which has an elevation of 663m, but air photos suggest that this overflow does not happen often. The wetland empties to the east into Bear Creek via a narrow channel. 4.3.6

Hermit Lake, Flyingshot Lake and Downstream Conveyance

Hermit Lake, covering a surface area of about 2.1 km2, is a natural waterbody located just west of the City. The east part of the Lake is within City limits, and a small undeveloped part of the City drains directly into it. The total drainage basin area of Hermit Lake is 23 km2 and

Sameng Inc.

4.3

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

its normal water level is about 665m AMSL. Hermit Lake outlets to the southeast and into a wetland just northwest of Flyingshot Lake. Flyingshot Lake, covering a surface area of 1.3 km2, is a natural waterbody located immediately southwest of the City, west of 116 Street and in line with 68 Avenue. A large wetland, about the same size of the Lake, is located northwest of the Lake. The total drainage basin area of Flyingshot Lake is 63 kmÂ˛, and its normal water level is about 651m AMSL. Part of the City (mostly undeveloped) drains into Flyingshot Lake as well as into the upstream wetland and watercourse. The conveyance channel going from Flyingshot Lake to Bear Creek is a well-defined watercourse that conveys a total drainage area of 71 km2 into Bear Creek. In addition to conveying drainage from Flyingshot Lake, it also collects drainage from the southwest part of the City including parts of Pinnacle Ridge and Oâ&#x20AC;&#x2122;Brien Lake. 4.3.7

Crystal Lake and Downstream Conveyance

Crystal Lake, covering a surface area of 0.38 km2, is a natural waterbody located northeast in the City. A wetland is located just northwest of Crystal Lake and is connected to the Lake. The total drainage basin area of Crystal Lake is about 2.9 km2, and its high-water level is about 681.79m AMSL. Crystal Lake does not have a natural outlet. An overflow structure controls the maximum water level in the Lake to 681.79m; excess water is piped northeast and into a ditch northeast of the City along Secondary Highway 670. The neighbourhoods of Crystal Ridge, Crystal Lake Estates (north) and Lakeland drain directly into that Lake via the sewer system. Water quality into the Lake from these neighbourhood sewers is controlled by forebays and oil-grit separators. The Albinati Industrial and Northgate neighbourhoods also flow into this Lake via the wetland. 4.3.8

Unnamed Well-Defined Watercourse Northeast of City

The northeast corner of the City, which is mostly occupied by agricultural areas and wetlands, drains into two separate branches of a well-defined unnamed watercourse flowing in a southeast direction. This watercourse outlets into Bear Creek about 7km straight east of the City. 4.3.9

Clairmont Lake

Drainage from a small area at the very northeast of the City drains into the Clairmont Lake watershed and into Clairmont Lake. Clairmont Lake, covering a surface area of 5.8 km2, is a natural waterbody located about 3 km northeast of the City. The total drainage basin area of Clairmont Lake is about 55 km2, and its normal water level is about 675m AMSL.

Sameng Inc.

4.4

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Clairmont Lakeâ&#x20AC;&#x2122;s outlet is west via Ferguson Lake and into Grande Prairie Creek which eventually flows back into Bear Creek and through the City. 4.3.10 Woody Channel The Woody Channel was constructed southeast in the City to provide drainage for the eastern part of the City that does not drain naturally to Bear Creek. The total basin area of the Woody Channel is 15 km2 at 68 Avenue and 18 km2 at the confluence with Bear Creek. The Woody Channel received drainage from many outfalls and ditches. Part of the flows into the Woody Channel is controlled by stormwater management facilities, and in other areas (even recent developments), runoff enters the Woody Channel uncontrolled. The man-made portion of the Woody Channel, which was recently improved in 2008, starts at the southeast corner of the Resources Road and 88 Avenue intersection at an elevation of 650.5m. From there, it flows in a southeast direction at a slope of about 0.1% and crosses the railroad tracks, 92 Street, a sanitary trunk, the future 72 Avenue and finally reaches 68 Avenue (bottom elevation of Channel at 68 Avenue is estimated to be around 646.0m). All crossings consist of many large culverts (up to 1800mm diameter) installed in parallel. South of 68 Avenue, the channel returns to a more natural meandering shape and outlets into Bear Creek about 500m south of the City boundary. Just upstream of 68 Avenue, the channel was designed as a stormwater management facility (SWMF #30) for the Signature Falls, Countryside North and a portion of the Eagle Estates neighbourhoods. For a distance of 1,100 metres upstream of the 68 Avenue crossing, water is stored permanently into the Channel, with the normal water level controlled to about 648.0m by three culverts installed just north of the 68 Avenue crossing. As mentioned above, the Woody Channel was improved in 2008 to allow increased drainage and additional development around the Channel. A report was prepared in 2006 to develop improvement concepts and document the recommendations. See Section 2.5 for a summary of this study. The North East Drainage Basin Study was completed in 2011 to develop a servicing plan for some developments tributary to the Woody Channel. See Section 2.5 for a summary of this study. 4.3.11 Wood Lake and Downstream Conveyance Wood Lake, covering a surface area of about 0.33 km2 (surface area changes depending on the year/season) is a natural waterbody located immediately east of the City. The west part of the Lake is within City limits, and a small mostly undeveloped part of the City drains directly into it. The total drainage basin area of Wood Lake is 4.5 km2 and its normal water level is about 647.7m AMSL. According to LiDAR, the natural overflow of the Lake is at an elevation of about 648.1m at the northeast end of the Lake, although the downstream channel is not very well-defined. Sameng Inc.

4.5

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Existing Stormwater Conveyance System 4.4.1

General

The City’s storm drainage system, illustrated in Figure 4-6, consists of about 226 km of storm pipes, 18 km of catchbasin leads, 2940 manholes, 1940 catchbasin manholes, 2470 catchbasins, 97 storm outfalls, 43 stormwater management facilities, 18 orifices, 13 weirs, as well as an unknown number of private sewers. There are also areas of the city served by roadside and backlot swales and ditches, which includes about 530 individual culvert crossings. As shown in Figure 4-6, Most of the developed areas of the City, with a few exceptions, are serviced by a system of storm sewer pipes and stormwater management facilities. 4.4.2

Drainage Asset Management

4.4.2.1 Overview The City maintains a GIS electronic database (available at data.cityofgp.com) of various components of the City’s drainage system. The storm sewer system information (i.e. Storm CB, Storm Lines, Storm MH) was downloaded from the “Storm Sewer” database and used for purposes of completing an inventory of the storm drainage system as well as the construction of the computer model. The process of using this information for purposes of computer modeling was very challenging given the significant gaps in information as well as missing key information for each pipe, manhole and catchbasin. For modeling purposes, gaps and inconsistencies with the data were estimated or assumed based on the surrounding pipe network, record drawings, other existing computer models, or information provided by the City. The following summarized the drainage information that is available in these databases, as well as recommendations to the City’s drainage asset management. 4.4.2.2 Storm Sewer Pipes The “Storm Line” file is a database that includes 5656 storm lines, 91 storm line stubs, 2377 catchbasin leads and 531 pipes with no description (most are believed to be culverts). This database provides relevant information for each pipe including diameter, length, invert elevations and ground elevations, pipe material, slope, abandoned or not, private or not, amongst others. The shape file also has the alignment of the pipe. The following are some observations and comments: • The “Storm Lines” database is missing a few key pipe information such as the upstream and downstream manhole/catchbasin ID and coordinates. Without this information, it is impossible to know the location or direction of the pipe without a sewer layout map. Even with a map, it is not possible to know the direction of flow in these sewer pipes.

Sameng Inc.

4.6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

• The pipes do not appear to have a unique ID associated to them, although the database does include a field for UnitID. Many pipe segments do not have a UnitID (18% of them) or the UnitID is duplicated with others (2%). Furthermore, for the pipes that do have an ID, many do not appear to follow any sort of ID naming procedure. • Out of the 5648 storm lines and stubs that are not identified as abandoned, 12% (705) do not have a diameter, 14% (766) do not have a length, 13% (733) do not have pipe material and an astonishing 34% (1911) are missing either the upstream or downstream invert elevation. It should be noted that many of these pipes with missing information are located on the airport site. The missing information is even greater for the catchbasin leads, and no information is available for the culverts (other than their location on the shape files). Furthermore, through a review of the data and through modeling, the diameter or invert elevation of many pipes were found to be doubtful or wrong. Missing and incorrect information was corrected/assumed on a case-by-case basis. • Many pipes do not connect to a manhole/catchbasin/tee either at the upstream or downstream end. This is mostly an issue when modeling the sewer system as the computer model requires each pipe to have an upstream and downstream node. 4.4.2.3 Manholes and Catchbasin Manholes The “Storm MH” file is a database that includes 2980 manholes and 1940 catchbasin manholes, and the “Storm CB” file is a database that includes 2473 catchbasins. These databases provide limited information about the manholes and catchbasins, but they do include whether the manhole/catchbasin is abandoned or not, private or not, amongst other information. The shape file also has the location of the infrastructure, but it does not always match with the pipe location. The following are some observations and comments: • The “Storm MH” and the “Storm CB” database is missing a few key manhole/node information such as the X and Y coordinate, barrel diameter/size, invert elevation, rim/ground elevation and cover type. This information is important to be able to locate the manhole (without the need of a map) and its physical properties. • The manholes and catchbasins do not appear to have a unique ID associated to them, although the database does include a field for UnitID. Many pipe segments do not have a UnitID (6% of manholes/catchbasin-manholes and 15% of catchbasins) or the UnitID is duplicated with others (0.1% of all). • Many manholes identified as manhole in the “manhole_ty” field are actually identified as catchbasin manholes in the “unittype” field. Many manholes were also found to be catchbasin manhole through a review of site photos. • Many catchbasins and catchbasin manholes (as well as CB leads) are missing from the database and were found through a review of site photos.

Sameng Inc.

4.7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

4.4.2.4 Other Drainage Infrastructure • There are no database documenting important surface drainage features such as swales, ditches and conveyance channels. • There is no database documenting the location and sizing of stormwater management facilities and lakes (either above or below ground) on public or private properties. The City does have information and maps about stormwater management facilities on public spaces which was useful; but some of that information was found to be outdated, incorrect, missing or misplaced. • There is no database documenting the presence of orifices, weirs or oil/grit separator in the drainage system. Existing orifices, weirs and oil grit separators were found through a review of record drawings and were included in the computer model. 4.4.2.5 Drainage Asset Management Recommendations The following are some key asset management recommendations: • The City of Grande Prairie should develop a comprehensive asset management system involving several diverse sources of information such as GIS systems, record drawings, monitoring data, inspection results, fiscal information and operational performance. This asset management system would be continuously updated and include a comprehensive inventory of existing drainage asset, their condition, cost of replacement and prioritization, amongst others. • The City should complete a thorough inventory of its drainage infrastructure and include that information in databases. This includes, but is not limited to: sewer pipes, catchbasin leads, culverts, manholes, tees, pipe ends, catchbasins, catchbasin manholes, inlet and outlet structures, outfalls, stormwater management facilities, underground storage units, orifices, control structures, weirs, swales/ditches, service connections, etc. Although they do not belong to the City, some infrastructure on private properties should also be documented, especially storage facilities as they may have a significant impact on the performance of the City’s drainage system. • Every pipe, culverts, conveyance channels, manholes and other drainage infrastructure should have a unique ID for purposes of asset management and modeling. • Other manhole and pipe information that would be useful to include in the database is the year of installation (which was provided to us for the pipes through AutoCAD file); and most recent year of rehabilitation.

Sameng Inc.

4.8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

4.4.3

City of Grande Prairie

Piped Network

According to the above-mentioned databases, the City’s storm sewer network consists of about 226 km of storm pipes ranging in size from 100mm to 2300mm in diameter, and 18 km of catchbasin leads typically 300mm in diameter. Pipe size distribution is summarized in Figure 4-1 and illustrated in Figure 4-6. Majority (51%) of the pipes are 450mm in diameter or less. About 13% of the pipes are 1200mm in diameter or larger. The City’ storm sewer system also consists of an estimated 2940 manholes, 1940 catchbasin manholes and 2470 catchbasins. Furthermore, the sewer system also consists of an estimated 18 orifices and 13 weirs, mostly used to control the water level and flow rate out of stormwater management facilities.

>1200mm 45%

Pipe Diameter (mm)

901-1200mm 15%

601-900mm

PVC

54%

41%

CMP/CSP

43%

40%

451-600mm

Concrete Others/Unknown 29%

43%

301-450mm

19%

26%

42%

<=300mm

17%

28%

30%

44%

66%

28%

13%

22%

23%

10%

Unknown 0

10000

20000

30000

40000

50000

60000

70000

80000

Pipe Length (m) Note: Percentage along the right side is length of pipe in that category divided by total length of pipe (totals 100%)

Figure 4-1: Summary of Storm Pipes by Diameter and Material

Sameng Inc.

4.9

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

The length of pipe installed by decade is illustrated in the map of Figure 4-7 and the material of installed pipes is illustrated in the map of Figure 4-8. This information is summarized in Figure 4-2 below. AGE: About half of the City’s storm sewer system is less than 25 years old and about 12 % of the system is more than 50 years old, with some of the oldest pipes nearing 80 years. The average storm pipe age in the City is 28 years. As expected, the oldest pipes (> 50 years) are in the older parts of the City including the Central Business District, Avondale, VLA Montrose, Hillside, Swanavon, Highland Park and College Park. MATERIAL: Prior to 1970, almost all pipes were concrete. Between 1970 and 1990, there was a transition from concrete to corrugated steel pipe (CSP). After 1990, most pipes installed have been made from PVC, with concrete and steel pipes used where larger diameters were required. Today, about 43% of the pipes are made of PVC, 34% of concrete and 22% of CSP. As clearly shown in Figure 4-8, the older areas of the City are mostly serviced with concrete pipes and the newer neighbourhoods mostly have PVC pipes.

2%, Others/Unknown, 4,200

43%, PVC, 104,800

22%, CMP/CSP, 52,700

Concrete

CMP/CSP

Installation Year / Pipe Age

Unknown

1970-1979

68%

40%

45%

17%

11%

12%

2000-2009

88%

2010-2017

96%

10000

19%

29%

47% 50%

97%

1990-1999

CSP

1950-1959 96%

1980-1989

Others/Unknown

Concrete

1940-1949 100%

1960-1969

PVC

Unknown

34%, Concrete, 81,500

32%

20000

30000

40000

50000

60000

70000

80000

90000

100000

Pipe Length (m) Note: Percentage along the right side is length of pipe in that category divided by total length of pipe (totals 100%)

Figure 4-2: Summary of Storm Pipes by Installation Year and Material Sameng Inc.

4.10

Storm Drainage Master Plan 2018 Final Report (Revision 1)

4.4.4

City of Grande Prairie

Storm Outfalls

The City of Grande Prairie has an estimated 97 storm outfalls servicing various areas of the City: 64 into Bear Creek (or its tributaries), 2 in the Canfor Ditch, 16 in Woody Channel (or its tributaries), 6 in the Flyingshot Lake drainage system, 8 in Crystal Lake, and 1 in the unnamed channel system northeast of the City. All known outfalls in the City of Grande Prairie are illustrated in Figure 4-9 along with their tributary sewer pipes. A summary of these outfalls is provided in Table 4-1. It should be noted that pipes flowing into stormwater management facilities are not considered outfalls, neither are culverts along major drainage channels. Furthermore, decommissioned outfalls are not included in the table. The information provided in this table and on the figure comes from many sources of information and was not field-verified as part of this study. Outfalls along the Bear Creek Corridor have recently been assessed in great details as explained in Section 2.4, but there are no studies documenting the location and condition of the other storm outfalls. It is recommended that the City complete an outfall condition assessment study for all their outfalls. The “Stormwater Outfall Assessment along the Bear Creek within the City of Grande Prairie - Draft Report (Westhoff Engineering Resources, Inc., October 31, 2017)” provides a thorough review of existing outfalls in the Bear Creek. All the inspected outfalls were classified based on the level of damage (this is summarized in Table 4-1), and a priority ranking for rehabilitation was provided. 14 outfalls have been classified as having major damage, 13 outfalls were classified with moderate damage, 22 classified with minor damage, and 9 outfalls with no damage. For more information, the reader should review that report. The outfall numbering used in this report is consistent with the 2017 outfall assessment report; the outfall ID are different than the 2014 Drainage Master Plan. Outfall that have not been identified in any other reports were given a new ID. The City database did not have Outfall IDs. The following are outfall specific comments that should be reviewed/confirmed. • Outfall #4 and #68: These two outfalls appear to convey drainage from catchbasins at both ends of the Highway 43 Bridge crossing Bear Creek. These outfalls likely exist, although the 2017 study did not find/document these outfalls. • Outfall # 7: This outfall only services one or two catchbasins. If elevation permits, these catchbasins could be reconnected to the Outfall #8 system and Outfall #7 could be abandoned. • Outfall # 10: Its purpose should be determined; it is not in the City database. • Outfall # 11: Its purpose should be determined; it is not in the City database. • Outfall # 24: The existing gabion baskets downstream of this outfall was replaced by new gabion baskets in 2015/16. However, the 2017 outfall assessment report identified that there is major damage at this outfall, with scour and damage to the Sameng Inc.

4.11

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

gabion baskets and riprap. The design of the gabion basket erosion protection structure should be reviewed as to why it is failing so soon. • Outfall # 26: The location of this outfall, and layout of the pipes connecting to this outfall should be confirmed. There are discrepancies between the 2017 outfall report and the City’s sewer database. • Outfall # 27: This outfall only services a few catchbasins. If elevation permits, these catchbasins could be reconnected to the Outfall #28 system and Outfall #27 could be abandoned. • Outfall # 30: This outfall only services a few catchbasins. If elevation permits, these catchbasins could be reconnected to the Outfall #28 system and Outfall #30 could be abandoned. • Outfall # 34 and 35: These outfalls are in the same vicinity, but there does not seem to be a purpose to have two outfalls at this location. The tributary area of each outfall should be confirmed. • Outfall # 37: This existing outfall and erosion protection downstream of the outfall was recently replaced in 2015/16. However, the 2017 outfall assessment report identified that there is riprap along the discharge channel that has been partially washed out. The report considers the level of damage as moderate. • Outfall #45 and 48: These outfalls are in the same vicinity, but there does not seem to be a purpose to have two outfalls at this location. The tributary area of each outfall should be confirmed. • Outfall #55: Its purpose should be determined. • Outfall #57 and #70: There are two outfalls at the 84 Avenue bridge crossing according to the City database, although only one outfall was identified in the 2017 outfall inspection report. The City should review whether two outfalls exist. If only one outfall exists, then the sewer database should be corrected. • Outfall #58 is identified as an outfall in the 2017 outfall assessment report, but it is the inlet of a dry pond (Pond #21), not an outfall. Consequently, it is not considered an outfall in this Master Plan. • Outfall #63: Its purpose should be determined. It likely has a small drainage area. • Outfall #69 was not identified in the 2017 outfall assessment report. It appears to convey drainage from a private commercial site to the Creek via a swale. • Many outfalls have very small drainage areas, some with as little as two catchbasins. The possibility to reconnect these sewer systems to other outfalls should be investigated, especially if the outfall needs repair or replacement. Reducing the number of outfalls in the receiving watercourse reduces the negative environmental impact that these outfalls might cause, including sedimentation and erosion.

Sameng Inc.

4.12

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table 4-1: Summary of Storm Sewer Outfalls Discharges to

Pipe Size / Diameter (mm)

Existing Level of Damage (according to October 2017 Outfall Assessment report 1)

Bear Creek

1500

Major (has since been replaced)

Bear Creek

1800

Minor

Bear Creek

1600

No Damage

Bear Creek

300

Unknown - Outfall Missing

Bear Creek

800

Major

Bear Creek

300

Minor

Bear Creek

370

Minor

Bear Creek

600

Major

Bear Creek

600

Minor

10 *

Bear Creek

450

Moderate

11 *

Bear Creek

600

No Damage

Bear Creek

450

Minor

Bear Creek

1050

Moderate

Bear Creek

300

Major

Bear Creek

400

Minor

Bear Creek

200

Minor

Bear Creek

800

Moderate

Bear Creek

1200

Minor

19 *

Bear Creek

300

Major

20 *

Bear Creek

300

Moderate

Bear Creek

400

Minor

22 *

Bear Creek

250

No Damage

Bear Creek

900

Minor

Bear Creek

1500

Major

Bear Creek

800

Moderate

Bear Creek

400

Minor

Bear Creek

300

Minor

Bear Creek

600

Major

Bear Creek

300

Moderate

Bear Creek

250

Major

Bear Creek

400

Moderate

35 *

Bear Creek

600

No Damage

Bear Creek

1200

Moderate

Bear Creek

400

Major

40 *

Bear Creek

450

Moderate

Bear Creek

400

Major

Outfall ID

Sameng Inc.

4.13

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Discharges to

Pipe Size / Diameter (mm)

Existing Level of Damage (according to October 2017 Outfall Assessment report 1)

Bear Creek

600

Minor

Bear Creek

1830

Minor

Bear Creek

1200

Major

45 *

Bear Creek

700

Minor

Bear Creek

900

Moderate

Bear Creek

1200

Moderate

Bear Creek

375

Major

Bear Creek

300

Minor

Bear Creek

300

Major

Bear Creek

300

Major

Bear Creek

600

Minor

55 *

Bear Creek

350

Minor

Bear Creek

450

Moderate

Bear Creek

450

Minor

59 *

Bear Creek

600

Moderate

60 *

Bear Creek

300

No Damage

Bear Creek

600

Minor

Bear Creek

900

No Damage

63 *

Bear Creek

300

No Damage

Bear Creek

450

No Damage

Bear Creek

600

Minor

Bear Creek

900

No Damage

68 *

Bear Creek

300

Unknown - Outfall Not Inspected

Bear Creek

450

Unknown - Outfall Not Inspected

Bear Creek

450

Unknown - Outfall Not Inspected

Canfor Ditch

1050

Unknown - Outfall Not Inspected

Canfor Ditch

1800

Unknown - Outfall Not Inspected

100

Woody Channel

1200

Unknown - Outfall Not Inspected

101

Woody Channel

1500

Unknown - Outfall Not Inspected

102

Woody Channel

1200

Unknown - Outfall Not Inspected

103

Woody Channel

525

Unknown - Outfall Not Inspected

104

Woody Channel (tributary)

1200

Unknown - Outfall Not Inspected

105

Woody Channel

900

Unknown - Outfall Not Inspected

106

Woody Channel

600

Unknown - Outfall Not Inspected

107

Woody Channel

300

Unknown - Outfall Not Inspected

108

Woody Channel

600

Unknown - Outfall Not Inspected

109

Woody Channel (tributary)

900

Unknown - Outfall Not Inspected

Outfall ID

Sameng Inc.

4.14

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Discharges to

Pipe Size / Diameter (mm)

Existing Level of Damage (according to October 2017 Outfall Assessment report 1)

110

Woody Channel (tributary)

1200

Unknown - Outfall Not Inspected

111

Woody Channel (tributary)

1050

Unknown - Outfall Not Inspected

112

Woody Channel

1200

Unknown - Outfall Not Inspected

150

Woody Channel (tributary)

900

Unknown - Outfall Not Inspected

151

Woody Channel (tributary)

400

Unknown - Outfall Not Inspected

152

Woody Channel (tributary)

900

Unknown - Outfall Not Inspected

200

Channel Downstream of Flyingshot Lake (tributary)

750

Unknown - Outfall Not Inspected

201

Channel Downstream of Flyingshot Lake

900

Unknown - Outfall Not Inspected

202

Channel Downstream of Flyingshot Lake (tributary)

525

Unknown - Outfall Not Inspected

203

Channel Downstream of Flyingshot Lake (tributary)

600

Unknown - Outfall Not Inspected

300

Bear Creek (tributary)

750

Unknown - Outfall Not Inspected

301

Bear Creek (tributary)

500

Unknown - Outfall Not Inspected

302

Bear Creek (tributary)

Unknown

Unknown - Outfall Not Inspected

303

Flyingshot Lake (tributary)

750

Unknown - Outfall Not Inspected

304

Flyingshot Lake (tributary)

1200

Unknown - Outfall Not Inspected

400

Unnamed Channel northeast of City (tributary)

525

Unknown - Outfall Not Inspected

401

Crystal Lake (NW wetland)

600

Unknown - Outfall Not Inspected

402

Crystal Lake (NW wetland)

750

Unknown - Outfall Not Inspected

403

Crystal Lake

300

Unknown - Outfall Not Inspected

404

Crystal Lake

300

Unknown - Outfall Not Inspected

405

Crystal Lake

750

Unknown - Outfall Not Inspected

406

Crystal Lake

525

Unknown - Outfall Not Inspected

407

Crystal Lake

525

Unknown - Outfall Not Inspected

408

Crystal Lake

750

Unknown - Outfall Not Inspected

Outfall ID

Stormwater Outfall Assessment along the Bear Creek within the City of Grande Prairie - Draft Report (Westhoff Engineering Resources, Inc., October 31, 2017) 1

Outfalls with a * besides their ID number were not modeled, as their catchment area was too small or it does not seem to form part of the City sewer system.

Sameng Inc.

4.15

Storm Drainage Master Plan 2018 Final Report (Revision 1)

4.4.5

City of Grande Prairie

Ditch Network

Portions of the City drainage network is composed of ditches, many of which are located along roads. The areas served primarily by ditches and surface drainage are shown in Figure 4-6. They include most of the undeveloped rural areas as well as a few developed areas including: Brochu Industrial, Richmond Industrial (south of 84 Avenue), the northeast part of Northridge, the north part of Northgate, Albinati Industrial, Eagle Estates, the industrial area south of Smith, a large mostly undeveloped area along Resources Road and the adjacent railroad, the Canfor site, and a few arterial roads/highways. 4.4.6

Major Drainage Channels

In addition to Bear Creek and watercourses that service large drainage basins, there are a few other important drainage channels in the City. They are: • Woody Channel at the southeast of the City (see Section 4.3.10 for details). • A south-flowing channel west of 84 Street going from the wetland south of 116 Avenue, along the east of Trumpeter Village and Crystal Landing, through Meadowview and Swan City, then through Fieldbrook and Eagle Estates and into the Woody Channel just north of Signature Falls. This partly-natural and partly-manmade channel conveys drainage for a large developed and to-be-developed area east in the City in the Woody Channel. Along the way, this drainage channel crosses 100 Avenue (via SWMF #27 and Outfall #150), flows through SWMF #49 in Fieldbrook, and across three local roads in Eagle Estates. • The Canfor Ditch running through the Canfor site from west-to-east and discharging into Bear Creek via Outfall #37. This channel receives and conveys drainage from the Richmond Industrial Area, the Central West Business Park and the Vision West Business Park via Outfalls #71 and #72, as well as from the Canfor site itself. Four large culverts are located along the channel to allow vehicular crossing of the Channel within the Canfor site; they are (from upstream to downstream) 1600mm, 2500mm, 2500mm and 2300mm in diameter. • A ditch both upstream (west of 108 Street collecting drainage from Outfall #203 and discharging into O’Brien Lake) and downstream (crossing 112 Street, 60 Avenue and 59 Avenue) of O’Brien Lake conveys drainage through the Lake and into O’Brien Lake (SWMF #44) and then into the channel downstream of Flyingshot Lake. The following channels and ditches are not as vital to the City’s drainage system, but are worth mentioning: • Ditches on both the north and south side of the railroad in the Richmond Industrial Area convey major drainage overflow east towards 108 Street and into Bear Creek. The size and location of any culverts crossing 108 Street are unknown, but one is believed to exist on the north side of the railroad.

Sameng Inc.

4.16

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

• An east-flowing ditch north of Westgate and Gateway (east of 116 Street) conveys runoff from the large undeveloped area to the north into the Outfall #3 sewer system and Bear Creek. Some of that water is intercepted by SWMF #42 prior to discharging to the outfall. The ditch crosses 110 Street. It prevents drainage from flowing into the developed areas. This channel will likely be abandoned once the area develops. • A west-flowing channel along the south of 116 Avenue from 100 Street to Bear Creek conveys surface runoff and major drainage overflow from the area into Outfall #1 and into Bear Creek. The ditch crosses 116 Avenue (Highway 43) just west of 100 Street, and 102 Street. It then crosses 116 Avenue and 106 Street via a storm pipe. • Ditches on both sides of Highway 43 west of 116 Street convey drainage to the Outfall #37 and #3 sewer systems. These ditches cross 124 Street, 120 Street and are intercepted by the sewer system just west of 116 Street. • The are many important ditches along the north-south railroad track east of Bear Creek, especially south of 92 Avenue and east of the railroad through the industrial area and into the Woody Channel. 4.4.7

Catchbasins

There is an estimated 1940 catchbasin manholes and 2470 catchbasins currently installed throughout the City, not including catchbasins on private properties (e.g. commercial parking lot). The distribution of catchbasins in the City is illustrated in Figure 4-10. The newer neighbourhoods generally have more catchbasins than the older areas, and their distribution throughout the neighbourhood is more consistent, generally spaced less than 150 metres apart. One exception is the Central Business District which appears to have the highest concentration of catchbasins in the City. In many of the more mature neighbourhoods, runoff has to flow a long distance, more than 500 metres in some instances, and cross many roads prior to reaching a catchbasin. This layout and large distance between catchbasins would not be allowed under the current design standards. This includes neighbourhoods such as Mountview, Hillside, Smith, Highland Park, Patterson Place, amongst others. Preliminary analysis and computer modeling results suggest that street flooding is often a result of small pipes restricting the flows, not the lack of catchbasins. In other words, adding more catchbasins to an area that experiences flooding may not necessarily reduce flooding and flood risks.

Sameng Inc.

4.17

Storm Drainage Master Plan 2018 Final Report (Revision 1)

4.4.8

City of Grande Prairie

Stormwater Management Facilities (SWMFs)

4.4.8.1 Overview The City’s storm system currently includes 43 City-managed stormwater management facilities (SWMFs). Twenty-five (25) are wet ponds and wetlands, fifteen (15) are dry ponds, and three (3) are forebays. There is also an additional wet pond on private development. A summary of the City’s SWMFs is provided in Table 4-2 and in Figure 4-3. The locations of the facilities are illustrated in Figure 4-11. A detailed summary of each facility is included under Appendix C. The SWMF ID numbering used in this report is consistent with the City of Grande Prairie SWMF database, but not with the 2014 Drainage Master Plan. The following are general comments and observations about the SWMFs: • Nearly all the City’s SWMFs were constructed after 1993. • Most of the SWMFs constructed before 2000 were dry ponds, while those constructed after 2000 were typically wet ponds. • SWMF # 15 and #18 were not designed for stormwater retention purposes. • Many of the newly constructed ponds are not yet constructed to their ultimate size, but to an interim size.

Figure 4-3: SWMF in the City of Grande Prairie over the Years

Sameng Inc.

4.18

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table 4-2: Summary of Stormwater Management Facilities Pond ID

Name / Location

Ivy Lake

Crystal Lake Estates Woodgrove

Country Club West

Mountview

Four Winds

Scenic Ridge

Royal Oaks

Country Side South

Pinnacle Ridge

Crystal Village

Resources and 68th

Resources and 76th

Westgate East

Crystal Lake

Fire Hall

Crystal Ridge FF1

SWMF Type 1 Wet Pond (direct flow) Dry Pond (controlled surge pond)

Year of Catchment Construction Area 1980

130 ha

1993

52 ha

1995

33 ha

Late 1990's

65 ha

1997

30 ha

1997

14 ha

1999

65 ha

1996

93 ha

2004

64 ha

Between 1997 and 2005

14 ha

1999

13 ha

1999

13 ha

2008-2010

61 ha

2000 - 2004

20 ha

Unknown

N/A

Forebay (wet facility)

1978

12 ha

Crystal Ridge FF2

Forebay (wet facility)

1979

14 ha

Muskoseepi Park Fish Pond

Wet Pond (Recreational)

Unknown

N/A

Community Knowledge Campus

Dry Pond (controlled surge pond)

Late 1990's

60 ha

Crystal Lake Estates

2003

36 ha

South Bear Creek

1999

15 ha

Westpointe at 84th Avenue

2002 - 2005

79.97 ha

Westgate West

2010

120 ha

Northridge Residential

2006

55 ha

O'Brien Lake

2005

114 ha

Dry Pond (controlled surge pond) Dry Pond (surge pond) Dry Pond (direct flow) Dry Pond (controlled surge pond) Dry Pond (controlled surge pond) Wet Pond (direct flow) Wet Pond (direct flow) Dry Pond (controlled surge pond) Wetland (direct flow) Wet Pond (direct flow) Wet Pond (direct flow) Wetland / Lake (Natural) (direct flow) Wet Pond (used for diving/training purposes)

Wet Pond (direct flow) Dry Pond (controlled surge pond) Dry Pond (controlled surge pond) Dry Pond (controlled surge pond) Dry Pond (controlled surge pond) Wet Pond (Natural) (direct flow)

Sameng Inc.

4.19

Storm Drainage Master Plan 2018 Final Report (Revision 1)

Pond ID

Name / Location

Pinnacle West

Crystal Landing

Woody Channel

Signature Falls

City of Grande Prairie

SWMF Type 1 Wet Pond (direct flow) Wetland (direct flow) Wet Pond / Conveyance Channel (direct flow) Wet Pond (direct flow)

Year of Catchment Construction Area 2006

43 ha

2005

45 ha (direct)

2007

N/A

2006/2007

40 ha

Centre West #1

Dry Pond (controlled surge pond)

2008 & 2015

168 ha (design report) 105 ha (measured)

Albinati Forebay

Forebay (wet facility)

2003

5.0 ha

2016

14 ha

Wet Pond (direct flow) Wet Pond (direct flow) Dry Pond (controlled surge pond) Dry Pond (controlled surge pond) Wet Pond (direct flow)

2016

8 ha (direct)

2010 - 2013

30 ha

2016

50 ha

2012

75 ha

Wet Pond (direct flow)

2017

25 ha (Current)

2016

63 ha

2013

60 ha

2016

44 ha

2016

44 ha

2014

63 ha

Stone Ridge #2

Grande Banks

Vision West

Kensington

Royal Oaks North

Grande Prairie Regional Hospital

Trader Ridge

O'Brien Lake West #1

Arbour Hills I #1

Arbour Hills I #2

Arbour Hills II

Fieldbrook

Wet Pond (direct flow)

2013

7.2 ha + Creek from N

PR01

Trumpeter Village (private)

Wet Pond (direct flow)

Unknown

N/A

Wet Pond (direct flow) Wet Pond (direct flow) Wet Pond (direct flow) Wet Pond (direct flow) Wet Pond (direct flow)

1 A “Direct Flow” pond means that all sewer drainage flows from the upstream basin flow into the pond. A “surge” pond is a pond where low flows normally bypass the pond but will backflow into the pond during larger rainfall/flow events due to the presence of an orifice or other control structure (controlled surge pond) or simply due to a lack of capacity in the downstream system (surge pond).

Sameng Inc.

4.20

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

4.4.8.2 Pond Types Each pond was categorized into one of the following pond types depending on the system layout and their quality and quantity control capabilities. • Wet ponds and wetlands have their inlets, and consequently all upstream flows, directed into the pond for all storm events. Wet ponds offer both quality control and quantity control of stormwater. ▪ The Woody Channel pond (SWMF #30) is considered a wet pond, although it was constructed in-line with the Channel. It serves similar purposes as a wet pond. • Dry ponds were divided in three different categories: ▪ Surge ponds typically only fill with water when the surrounding sewer system is surcharged, typically for events larger than a 2-year return period. They offer very little water quality benefit and their peak flows into the downstream system is uncontrolled. ▪ Controlled surge ponds: Similar to surge ponds, controlled surge ponds only fill with water during the larger rainfall events. The difference is that controlled surge ponds have a control structure (e.g. orifice) in the downstream system that controls the peak outflows to the downstream system. Consequently, controlled surge ponds can often have some water flowing into the pond many times per year, depending on the downstream control. They offer very little water quality benefit during the frequent storm events, although they do provide quantity control. ▪ Flow-through dry ponds: Similar to wet ponds, flow-through dry ponds have drainage from their tributary catchments flow directly into the SWMF prior to flowing downstream, although the pond is normally dry when it is not raining. This pond will provide some quality benefits and normally controls peak flows into the downstream system. • There are three (3) forebays in the City: two are west of Crystal Lake, controlling water quality into the Lake from the residential area; and another north of Crystal Lake in the industrial area, serving a similar purpose. • 4.4.8.3 Natural Water Features • Some ponds were created from natural water features including: ▪ SWMF #11: This natural wetland located northeast of the 68 Avenue and Resources Road intersection was repurposed as a stormwater management facility. ▪ SWMF #14: Crystal Lake – Natural Lake – Water quality into this facility is controlled by many of oil-grit separators (at all outfalls north of the Lake) as well as two forebays to the west (SWMF #16 and #17). ▪ SWMF #25: O’Brien Lake – Natural Lake ▪ SWMF #27: The Crystal Landing wetland is a natural wetland that was repurposed as a SWMF. It discharges into another wetland to the south.

Sameng Inc.

4.21

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

▪ SWMF #30: Woody Channel – The downstream end of this channel was rerouted and enlarged and will offer some storage capacity. ▪ SWMF #41: The Royal Oaks North wet pond was constructed where a small waterbody once existed. 4.4.8.4 Control Structures • There are many types of control structures used throughout the City to control peak flows and water levels out of SWMFs. These are explained for each facility in Appendix C. • The normal water level (NWL) in wet ponds is often controlled by the elevation of the downstream outlet pipe, and in some cases by the elevation of the downstream orifice or weir. • Flow rates are often controlled by an orifice or vortex flow regulator (e.g. Hydrovex) installed in the downstream sewers. In some locations, the flow rate is controlled by the smaller size of the downstream sewers. • A few SWMFs have emergency overflow weir structures inside the storm sewer system, but most of them have overflows channels at a specific location along the perimeter of the pond.

Sameng Inc.

4.22

Storm Drainage Master Plan 2018 Final Report (Revision 1)

4.4.9

City of Grande Prairie

Quality Treatment Devices

In addition to the many stormwater management facilities (i.e. wet ponds) which provide water quality enhancements, there are 5 oil-grit separators and 3 forebays in the City. All (except one) are located upstream of Crystal Lake. The performance of these facilities to reduce sediment loads and improve water quality in the receiving watercourses/waterbodies is unknown. It is recommended that the City studies the effectiveness of these facilities in improving water quality.

OIL-GRIT SEPARATOR: -

Upstream of Outfall #405: Stormceptor STC-4000

Upstream of Outfall #406: Stormceptor STC-2000

Upstream of Outfall #407: Stormceptor STC-2000

Upstream of Outfall #408: Stormceptor STC-4000

Northeast Corner of 89th Avenue and 116th Street

FOREBAY: • Upstream of Outfall #403: See SWMF #17 in Section 4.4.8. • Upstream of Outfall #404: See SWMF #16 in Section 4.4.8. • Upstream of Crystal Lake NW Wetland; See SWMF #34 in Section 4.4.8.

Sameng Inc.

4.23

HIGHWAY 2

LEGEND CLAIRMONT LAKE

CITY BOUNDARY PROPERTY LINE

BEAR CREEK

BEAR LAKE

LAKE WATERCOURSE / WATERBODY BASIN BOUNDARY

BEAR LAKE WATERSHED

HIGHWAY 43X

TWP RD 722

HIGHWAY

HIGHWAY 43

CLAIRMONT LAKE WATERSHED LiDAR ELEVATION LEGEND HIGHWAY 43

710m

HERMIT LAKE WATERSHED

700m

148 AVENUE

690m

NORTHEAST UNNAMED CHANNEL WATERSHED #2

HUGHES LAKE WATERSHED

HERMIT LAKE

132 AVENUE

670m 660m 650m 640m 630m

SECONDARY HIGHWAY 670

TWP RD 720

680m

NORTHEAST UNNAMED CHANNEL WATERSHED #1

HIGHWAY 43X

100 STREET

E CR

HUGHES LAKE

BEAR CREEK WATERSHED (DOWNSTREAM OF BEAR LAKE TO CITY BOUNDARY)

CRYSTAL LAKE WATERSHED CRYSTAL LAKE

BE AR

116 AVENUE

E CR

108 STREET

HIGHWAY 40

116 STREET

124 STREET

84 AVENUE

RGE RD 54

WOOD LAKE

Prepared By:

CES

OUR

FLYINGSHOT LAKE WATERSHED

WOOD LAKE WATERSHED

RES

RGE RD 65

RGE RD 70

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

D ROA

Client:

68 AVENUE

FLYINGSHOT LAKE

AKE

BE AR

IEN L O'BR

CR EE

TWP RD 712

Project:

Storm Drainage Master Plan 2018

REEK

DOWNSTREAM OF FLYINGSHOT LAKE WATERSHED

TWP RD 710

HIGHWAY 40

RGE RD 71

WOODY CHANNEL WATERSHED

RGE RD 53

TWP RD 714

100 AVENUE 92 STREET

100 AVENUE

84 STREET

HIGHWAY 43

108 AVENUE RESERVOIR

BEAR C

Title: BEAR CREEK

Topography and Major Basins (City Area)

Scale:

Figure:

N.T.S.

4-4

S. HIGHWAY 731

LEGEND CITY BOUNDARY PROPERTY LINE

S. HIGHWAY 677

LAKE WATERCOURSE / WATERBODY

S. HIGHWAY 724

BASIN BOUNDARY HIGHWAY

AY 2 HIGHW

BE WEB

LiDAR ELEVATION LEGEND

EEK

R CR

1000m 950m 900m 850m 800m 750m 700m 650m 600m 550m 500m

BEAR LAKE WATERSHED BEA

MUL

LIGA

N CR

EEK

GRANDE PRAIRIE CREEK WATERSHED

HIGHWAY 59 S. HIGHWAY 721

BUFFALO LAKE LA GLACE LAKE HIGHWAY 59

S. HIGHWAY 674

P NDE

GRA EEK

K CREE

IE CR

RAIR

BEAR

HIGHWAY 672

COLQUH OUN CR

EEK

S. HIGHWAY 724

CLAIRMONT LAKE

BEAR LAKE

Prepared By: HIGHWAY 43

BE #1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

K EE CR

SASKATOON LAKE

CLAIRMONT LAKE WATERSHED

HIGHWAY 670 S. HIGHWAY 667

Client:

HIGHWAY 43

BEAR CREEK WATERSHED (DOWNSTREAM OF BEAR LAKE) Project:

Storm Drainage Master Plan 2018

BEAR CREE

Title: HIGHWAY 40

S. HIGHWAY 723

HIG

S. HIGHWAY 671

WAP

IVER

ITI R

Topography and Major Basins (Around City)

Scale:

Figure:

N.T.S.

4-5

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE PLANNED DEVELOPMENT AREA (TO BE SERVICED WITH SEWERS) STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE WATERCOURSE / WATERBODY AREAS DRAINED BY DITCH / SURFACE DRAINAGE

132 AVENUE

A BE

TWP RD 720

AREAS DRAINED BY DITCH / SURFACE DRAINAGE (RURAL)

EE CR

100 STREET

AREAS DRAINED BY PRIVATE STORM SEWER NETWORK

PIPE SIZE LEGEND

CRYSTAL LAKE

0mm - 300mm 375mm - 450mm

AR BE

525mm - 600mm

116 AVENUE

K EE

675mm - 900mm 1050mm - 1200mm 1350mm - 1650mm > 1800mm

108 AVENUE RESERVOIR

100 AVENUE

108 STREET

116 STREET

124 STREET

84 AVENUE

RGE RD 54

84 STREET

WOOD LAKE

Prepared By:

AD S RO

E URC

O RES #1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN L

AKE

Project:

Storm Drainage Master Plan 2018

O'BR

CR E

FLYINGSHOT LAKE

RGE RD 65

92 STREET

100 AVENUE

Title:

Existing Drainage Network / Pipe Size Scale:

Figure:

1:40,000

4-6

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE WATERCOURSE / WATERBODY 600 CSP 2015

STORM PIPE BY YEAR CONSTRUCTED 1940 - 1949

132 AVENUE

A BE

TWP RD 720

600 CSP 2016 12.00

BRK

1950 - 1959

EE CR

1960 - 1969 INT

INT

100 STREET

1970 - 1979 900

CSP

2000

50.00

1980 - 1989 1990 - 1999

INT

CRYSTAL LAKE

2000 - 2009

IN/OUTLET

2010 - 2018

IN/OUTLET

600 CSP 2001 800 CSP XXXX 38.00 800 CSP XXXX 38.00 600 CSP 2007 19.00 0.50

(ABDN)

UNKNOWN

116 AVENUE BRK

(ABDN)

AR BE

(ABDN)

INT

300 CSP XXXX

(ABDN)

2014

(ABDN)

K EE

200 PDP

INT

300 CSP

INT

300 CSP

(ABDN)

200 PDP

300 PVC

(ABDN)

600 CSP 2007 19.00

0.50

(ABDN)

600 CMP

450 CONC

450 CMP

600 CSP 2007 28.00

(ABDN)

450 CMP

450 CONC

(ABDN)

750 CONC

450 CMP 500

450 CMP

CSP

500 CSP

108 AVENUE

450 CMP

400

500 CSP

BRK

PVC 300

(ABDN)

300

450 PVC

PVC

450 PVC

RESERVOIR

(ABDN)

300

CONC

450

(ABDN)

PVC

200

PDP

900

PVC

(ABDN)

BRK

300 PVC 2006 300 PVC 2006 5.00

IN/OUTLET

(ABDN)

200

IN/OUTLET

BRK

300 PVC 2006 6.00

BRK

INT

100 AVENUE

23.99 AUGERED SECTION 22.98 AUGERED SECTION

BRK

1.75 4.00 1996 0.00 PVC 0.00 300 1996 PVC

WOOD LAKE

300 CSP 2009 18.30 7.40

116 STREET

84 AVENUE

Prepared By:

INT

600 CSP

124 STREET

300 PVC 2014 3.64 2.00

2015

O RES

BRK

400 CSP 2012

400 CSP

E URC

250 CSP 2012 6.00 0.83

INT

AD S RO

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

INT

Client:

1.00

PVC

300

300 300 PVC 1.00

300 PVC 1.00

68 AVENUE

FLYINGSHOT LAKE

600 CSP XXXX 47.37 0.50

AKE

Project:

CR E

IEN L

Storm Drainage Master Plan 2018

O'BR

RGE RD 65

200

INT

108 STREET

INT

RGE RD 54

39.98 AUGERED SECTION

84 STREET

INT

750 CONC 750 CONC

92 STREET

100 AVENUE 750 CONC

INT

Title: IN/OUTLET

Pipe Age Scale:

Figure:

1:40,000

4-7

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE WATERCOURSE / WATERBODY

STORM PIPE MATERIAL CONCRETE

132 AVENUE BRK

A BE

TWP RD 720

200 PVC 1996 20.70 0.00

CSP OR CMP INT

EE CR

0.43

71.56

PVC OR HDPE

600 CONC 2014 18.00

INT

UNKNOWN

INT

100 STREET

INT

500 CONC 2008 20.00 1.50

500 CSP 2008 20.00

INT

INT INT

INT

INT INT

INT

CRYSTAL LAKE

INT

INT INT

750 NPP

INT

IN/OUTLET

450 1974 0.00 450 1974

INT

0.00 450 1974 0.00

IN/OUTLET

750 NPP

INT INT

200

600 CSP 2001

150 INT

150

525 1974 0.00

INT

200

750 NPP 200 300 WBD VT

750 NPP

500

CONC

250

200 PDP

250 PDP

250 WBD

200 PDP

300 WBD 250 PDP

200 PDP

(ABDN)

200 WBD

250 WBD 250 PDP

200 PDP

250 PDP 300 WSP

(ABDN)

200 PDP 300 WSP (ABDN)

200 PDP 250 WSP (ABDN)

(ABDN)

200 PDP 200 WSP

(ABDN)

200 WSP

(ABDN)

200 PDP

375 NPP

200 WSP

(ABDN)

200 PDP

250 WSP

450

375

(ABDN)

NPP

NPP (ABDN)

150

WSP

200

WBD 300 NPP

(ABDN)

150 VT (ABDN)

200 PDP

250 300 CONC

WSP 375 WSP

200 PDP

300

NPP

375 WSP

200 PDP

375 1987 0.00

K EE

200 PDP

150

375 375 0.00

300 NPP 250

200 PDP

375 1987 0.00

300 1987 0.00

200 PDP

BRK

250 PDP

116 AVENUE

200 PDP

300 WSP

1200 VCT 1973 30.50 0.28

200 WBD

375 WBD 200 PDP

200 PDP

250 PDP

(ABDN)

300 WBD

200 PDP

0.00

WBD 450 NPP

1974

200

200 PDP

300

VT VT

150

200 PDP 200 WBD

675 10.67 0.00

1200 VCT 1973 53.00 0.25

150 150

200 WBD 200 PDP

675 0.00

INT

BRK

675 1974 0.00

AR BE

WBD VT 200 150

150

200 PDP

INT

375 1968 0.50

INT

750 CSP 1969 12.20 0.64

BRK

WSP

300

(ABDN)

WSP

450

BRK

150

300 1996 28.50 8.50

PDP

2014

300

NPP

200

INT

2014 2014

300 1996 13.50 2.00

300 1996 30.00 9.80

WSP (ABDN)

450 300 1996 13.50 2.00

300

150

NPP

WSP VT

150

(ABDN)

450

WSP

WSP 300 PVC

PDP 200

1981

300 PVC 2011 12.20 4.50 300 1961

150

300

NPP

300 1961

INT

300

(ABDN)

150 VT

NPP

WSP

450 WSP

375

375 150 (ABDN)

150 375 VT WSP

150

300 ST 1981 50.70 0.50

300 ST 1981 57.00 0.50

300 ST 1981 45.60 0.98

200 PDP

CONC 600

100 PVC 1981 47.30 0.00

450 1981 53.61 0.86

WSP 525 VT 150

200 WBD VT

150

108 AVENUE

450 1981 73.40 0.78

BRK

200 PDP

150 200 VT WBD

300 1981

23.90 0.80

(ABDN)

1981

PVC

450

200 18.59

450

44.81

0.71

100 20.39

PVC 300

300 PVC 1996 6.40 0.00

600 PVC

300

150 VT

450 PVC

600

PVC

300

750

450

PVC

CONC

PVC 600

NPP

(ABDN)

RESERVOIR

PVC

150 VT

600

250 150 WSP VT

300

CONC

PDP

600 PVC

200

PDP

VT 150 WBD 200

PVC

250

200

PDP

200

PVC

600

CONC

NPP

200

(ABDN)

750

WBD

BRK

450 STL 40.10 0.00

450 STL 0.00

300 78.10 0.00

300 STL

27.50

PDP

450 STL 74.00 0.00 300 STL 32.40 0.00

NPP

19.00

525 1982

35.36

3.47

0.00

0.00 300 22.00

450 25.00 0.40 0.00

35.97 3.41

600 32.00

0.00

PDP

BRK

16.90

525 1983

INT

525 1983

BRK

450 1983

525

0.00

525 1983 0.00

200

300

24.00

82.30 0.00

VT WBD

150

200

375

0.00

22.50

525 1983 0.00 525 1983

INT

300

(ABDN)

525 1983 0.00

IN/OUTLET

29.70

525

WBD

IN/OUTLET

VT 150

0.00

200 VT

300

450 1984 53.50 1.30

450 1982 62.48 0.00

0.00

300 14.00 0.00 300 21.00 0.00

450 9.50 0.00

30.60

68.58 0.00

525 26.00

300 1982 25.30 0.00

300

0.00

39.10

0.00

1983 525

0.00 1983 525

0.00

525 1983 0.00 525 1983 0.00

150

300 55.00 0.00

40.70

0.00

27.43

300 34.80 0.00

525 CONC

19.81

1982

0.00

1982

300

0.00

375 1986 30.00 0.00

44.20

525 1983 0.00

0.00

300 25.00

525 1982

WBD 0.00

23.00

31.90 0.63

200

1983

300

525 CONC

VT 525

300 21.60

450 41.80 0.00

300

IN/OUTLET

300 21.50 0.00

0.00

(ABDN)

150

VT 150 WSP 250

300

525 1983 0.00

150

300

450 CONC 45.20 0.85

BRK

CONC

300 29.00

(ABDN)

200

300 STL

250 150 WSP VT

CONC

750

300

675

CONC

WBD

450 CONC 36.40 0.00

250

200

900

1200 CONC

0.00

600 CONC 1984 6.00 0.30 600 CONC 1984 16.50 0.22

600 CONC 53.00 0.31 525 1983 10.97 3.50

15.00 AUGERED

375 STL 70.30 (ABDN)

300 1984 50.50

150

WBD 200

INT

250 37.80 0.30

250 51.51 0.30

BRK

450 1983 0.00

INT

WBD

450 1983 74.68 0.00

200

0.44

450 1983 22.86 0.00

150

250 60.96 57.91 100

1984

300 CSP 1984

INT

74.90 0.79

INT

0.00 1983 375

INT

375 1971 42.98 0.25

0.24

375 1971 49.99 0.25

375 1971 42.06

375 1983 74.68 0.00

375 1971 12.80 0.50

0.00

BRK

1200 CSP 2000 94.03 0.12

375 1971 14.02 0.18

375

1983

375 1971 49.16 0.25

42.67

375 1971 17.07 0.25

BRK

200

31.09 VALVE 1984 PVC DRAINAGE POND

375 1971 38.86 0.25

BRK

100 AVENUE

INT

BRK

300 PVC 1996 17.00 0.00

INT

CMP 300

200

300 1986 20.20 3.10

300 1986 47.90 2.90

BRK

0 0.00

1969

0.97

300

22.90 0.00

22.50

1982 300

200

450 1980 0.00

200 1973

250 1973

450 1980 0.00

104.20

2.34

375

300 1973

21.00

11.18

5.07 200

1973

23.16

BRK

375 1980 0.00

300 1980 0.00

BRK

450 1986 92.70 0.34

100 1980

300 1980 0.00

450 1972 47.20 0.20

100 1980

300

1972

300 1980 0.00

300 PVC 2016 10.11

BRK

500 CMP 1980 16.50 0.00 BRK

BRK

INT

RGE RD 54

300 PVC 2016 7.01

300 1980 0.00

84 STREET

300 CSP 1996 6.2 0.00

1986

200

375 1980 0.00

375 1980 0.00 1980

300 2005

74.30

BRK

200 1973

100

1986

2.50

200 1973

92 STREET

INT

150 PVC 1996

450 1980 0.00

375 1981

100 AVENUE

INT

XXXX

BRK

108 STREET

116 STREET

INT

WOOD LAKE

BRK

250 300

300

375

200 PVC 2007 375

300

Prepared By:

INT

124 STREET

BRK BRK

84 AVENUE

INT

O RES

BRK

INT

INT INT

INT

300 1981

INT

E URC

INT INT INT

INT

750 PVC 2006 88.25 0.37 INT

AD S RO

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

INT

INT INT

Client:

INT BRK INT

INT

INT INT

BRK

INT

FLYINGSHOT LAKE

BRK

INT

BRK

68 AVENUE

INT

500 CSP 2005 16.00 INT INT

INT

Project:

CR E

AKE

IEN L

Storm Drainage Master Plan 2018

INT

O'BR

RGE RD 65

BRK

INT INT

Title: IN/OUTLET

Pipe Material Scale:

Figure:

1:40,000

4-8

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) WATERCOURSE / WATERBODY STORM PIPE (COLOURED BY TRIBUTARY OUTFALL)

OUTFALL LOCATION AND OUTFALL ID

401 400

402

132 AVENUE

A BE

TWP RD 720

408

INT

EE CR

405

406

INT

407

INT

100 STREET

INT

INT INT

INT

300

INT

INT INT

INT

302

403 INT

INT

404

INT

CRYSTAL LAKE

INT

INT INT

IN/OUTLET

INT

IN/OUTLET

IN/OUTLET INT INT

INT

AR BE

INT

151

63 7 8

INT

12 13 14

303

INT

INT INT

9 10 62

100 AVENUE

61 11

22 23 24

INT

17 19

500 CMP 1980 16.50 0.00

INT

30 33 34 & 35 64 39 70 56 40 69

71 & 72 84 AVENUE

37 57

43 INT

100 & 101

INT INT

INT

102 & 112

Prepared By:

INT

INT INT INT

INT

x2 x2

105

AD S RO

INT

103

E URC

WOOD LAKE

104

111

O RES

INT

116 STREET

108 STREET

SEE DETAIL

INT

124 STREET

INT

150

26 27

RGE RD 65

100 AVENUE

INT

RGE RD 54

INT

84 STREET

IN/OUTLET

108 AVENUE

92 STREET

IN/OUTLET

10.97

IN/OUTLET

RESERVOIR 12.19

304

152

116 AVENUE

6 & 60

K EE

4 3

5 59

INT

2 68

INT

301

Client:

INT

45 & 48

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

106 107

INT

INT INT

68 AVENUE

INT

INT INT

202

51 50

INT

203 INT

18 AKE

IEN L

Project:

INT INT

200

Storm Drainage Master Plan 2018

INT

O'BR

INT

CR E

INT

FLYINGSHOT LAKE

108

109 Title:

IN/OUTLET

201

Existing Outfalls and Tributary Sewer Pipes

110

24 Scale:

Figure:

1:40,000

4-9

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE WATER COURSE / WATERBODY STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE STORM PIPE CATCHBASIN / CATCHBASIN MANHOLE LOCATION

132 AVENUE

A BE

TWP RD 720 x2

100 STREET

EE CR

CRYSTAL LAKE

AR BE

116 AVENUE

K EE

108 AVENUE RESERVOIR

100 AVENUE

108 STREET

116 STREET

124 STREET

84 AVENUE

WOOD LAKE

Prepared By: O RES

x2 x2

AD S RO

E URC

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN L

AKE

Project:

Storm Drainage Master Plan 2018

O'BR

CR E

FLYINGSHOT LAKE

RGE RD 65

RGE RD 54

84 STREET

92 STREET

Title:

Catchbasin Distribution Scale:

Figure:

1:40,000

4-10

LEGEND

148 AVENUE

CITY BOUNDARY STORMWATER MANAGEMENT FACILITY (WET POND) STORMWATER MANAGEMENT FACILITY (DRY POND) LAKE WATERCOURSE / WATERBODY AREA DRAINS TO WET POND (DIRECT FLOW)

43 46

AREA DRAINS TO DRY POND (DIRECT FLOW)

132 AVENUE

AR BE

TWP RD 720

AREA DRAINS TO WET POND (CONTROLLED SURGE)

47 48

AREA DRAINS TO DRY POND (CONTROLLED SURGE) AREA DRAINS TO DRY POND (SURGE)

INT

AREA DRAINS THROUGH FOREBAY

INT

K EE CR

INT

100 STREET

INT

INT INT

INT

INT INT INT INT

INT

INT INT

INT

INT INT

IN/OUTLET

INT

IN/OUTLET

IN/OUTLET INT INT

POND ID NUMBER

14 L CRYSTA LAKE

INT

AREA DRAINS THROUGH OIL-GRIT SEPARATOR

INT INT

INT

C AR BE

116 AVENUE

INT

EK RE

02 INT

INT

108 AVENUE RESERVOIR

10.97

12.19

PR01

IN/OUTLET

INT

500 CMP 1980 16.50

0.00

INT

100 AVENUE

RGE RD 54

100 AVENUE

INT

84 STREET

INT

92 STREET

INT

108 STREET

116 STREET

WOOD LAKE

INT

124 STREET

INT

49 84 AVENUE

Prepared By: INT

RES

INT

INT INT

OUR

INT INT

INT INT INT

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

OAD

INT

Client:

INT

x2 x2

R CES

INT

INT INT

INT

INT INT

68 AVENUE

INT

FLYINGSHOT LAKE

INT

AKE

CR E

INT

Project:

03 INT

IEN L

O'BR

INT

36 25

Storm Drainage Master Plan 2018

RGE RD 65

NOTE: A "DIRECT FLOW" POND MEANS THAT ALL SEWER DRAINAGE FLOWS FROM THE UPSTREAM BASIN FLOW INTO THE POND. A "SURGE" POND IS A POND WHERE LOW FLOWS NORMALLY BYPASS THE POND BUT WILL BACKFLOW INTO THE POND DURING LARGER RAINFALL EVENTS DUE TO THE PRESENCE OF AN ORIFICE OR OTHER CONTROL STRUCTURE (CONTROLLED SURGE POND) OR SIMPLY DUE TO A LACK OF CAPACITY IN THE DOWNSTREAM SYSTEM (SURGE POND).

INT INT

44 IN/OUTLET

Title:

Existing Stormwater Management Facilities Scale:

Figure:

1:40,000

4-11

Storm Drainage Master Plan 2018 Final Report (Revision 1)

5.0

City of Grande Prairie

Rainfall and Flow Monitoring Data Analysis and Recommended Monitoring Program Overview

Rainfall and flow monitoring data within the City limits were collected and analyzed. The following is a summary of the main findings. Precipitation Normal As illustrated in Figure 5-1, The City of Grande Prairie sees most of its precipitation in the summer months, more precisely in June and July with an average of 76mm of precipitation each. The total average yearly precipitation is 445mm, with an average of 318mm falling between the months of May to October.

Figure 5-1: Temperature and Precipitation Graph for 1981 to 2010 Canadian Climate Normals for the Grande Prairie Airport (from climate.weather.gc.ca)

Sameng Inc.

5.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Rainfall 5.3.1

Rainfall Gauge Location and Data Availability

CITY OF GRANDE PRAIRIE RAINFALL GAUGES The City of Grande Prairie owns and operates three (3) rainfall gauges throughout the City as shown in Figure 5-26 and summarized in Table 5-1. The rain gauge catchment divide shown on Figure 5-26 indicate the portion of the City that each rain gauge would be attributed to if all locations are operating. Two of the City gauges (RG1 and RG2) have been collecting rainfall data since 2012, and another (RG3) since 2016. These gauges typically operate from May to September and are removed for the winter. The City uses electronic ‘tipping bucket’ style rain gauges that measure rainfall continuously. Table 5-1: Summary of City of Grande Prairie Rainfall Gauges Rain Gauge ID RG1

RG2

RG3

Location

Years of Record

West part of City 9505 112 Street Richmond Industrial Park Installed on roof of City building Southeast part of City 8111 Resources Road East of Patterson Place Installed on roof of Fire Hall North part of City 11906 102 Street Northridge Installed on roof of Fire Hall

2012 - 2017

2016 - 2017

AQUATERA RAINFALL GAUGES According to the 2012 Storm Drainage Master Plan (Section 2.4), Aquatera operates four (4) rainfall gauges throughout the City, typically operating between the months of May and October. They are said to be located at: • Country Club Estates Lift Station (west of Resources Road and south of 61 Avenue); • Service Centre (9505 112 Street) – same location as City’s RG1 (the City indicated that Aquatera does not have a rainfall gauge on the City’s Service Centre building); • Pump House #2 (northeast of 94 Street and 113 Avenue bend); • Pump House #3 (east of 97 Street and north of 133 Avenue). Aquatera was not contacted as part of this 2018 Master Plan Update. The accuracy of this information was not confirmed. Their rainfall data was not collected or reviewed. Sameng Inc.

5.2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

GOVERNMENT GAUGES The Government of Canada (Environment Canada) and Alberta Agriculture and Forestry have been collecting rainfall data near the City for many years. Environment Canada has been collecting and post-processing rainfall data in the area from the 1960s until 1993-94. Their closest gauges to the City are at the Grande Prairie Airport and in Beaverlodge (38 km west of City). Rainfall data at the airport is still being collected by NAV Canada but is only tabulated every six hours. Rainfall data for many other stations near Grande Prairie has been collected by Alberta Agriculture and Forestry (AAF) since the 2000s; they are all still operational. Data for these stations was tabulated every 15 minutes by AAF, but it is not quality controlled. Their closest gauges to the City are at Teepee Creek (32km northeast), Beaverlodge (38km west) and La Glace (40km northwest). For purposes of this study, we collected some of the government gauge’s rainfall data to update the City’s IDF curves and design rainfall events, as explained in further details in Section 3.2.3 of this report. However, since the only rainfall data in the City (i.e. Grande Prairie Airport) is only recorded every six hours, and therefore unsuitable for modeling and calibration purposes, it was not collected. 5.3.2

Data Quality Assurance

For quality assurance purposes, the rainfall data from the three City rainfall gauges were compared to one another and with the Spirit River Weather Radar, which is owned and operated by the Government of Canada (http://climate.weather.gc.ca/radar/index_e.html). The following was found: • The larger rainfall events were usually also observed by the Weather Radar and were recorded at more than one City rainfall gauges, providing confidence in the rainfall data. • For any given year, all gauges typically record similar amounts of rainfall, suggesting that the rainfall distribution is quite uniform throughout the City, and that the collected data is truthful. • For the Year 2012, the data from the rainfall gauges at RG1 and RG2 did not always correlate with the Weather Radar, and the measured rainfall at the two gauges did not correlate with one another. The 2012 data was considered erroneous for purposes of this study and was not evaluated furthermore. • Some of the high intensities recorded by the gauges appear to have been recorded during the installation and removal of the gauges and are not actual rainfall events. These records were discarded.

Sameng Inc.

5.3

Storm Drainage Master Plan 2018 Final Report (Revision 1)

5.3.3

City of Grande Prairie

Summary of Rainfall Data from 2013 to 2017

Figure 5-2 to Figure 5-6 illustrate the recorded rainfall from Year 2013 to 2017 (May to October) at the three City gauges (after the data considered erroneous was deleted). The figures show the rainfall intensity (averaged over 1-hour) and the cumulative rainfall depth over the year. Also shown on these figures is the rainfall intensity for the 90% POE (probability of exceedance in any given year); generally, this event is exceeded once or more per year. It should be noted that the total rainfall volume only considers the available data. For many years and many rain gauges, there are data gaps, especially at the beginning and end of the recorded data.

Sameng Inc.

5.4

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-2: Rainfall Data for the Year 2013 at RG1 and RG2 of the City of Grande Prairie

Sameng Inc.

5.5

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-3: Rainfall Data for the Year 2014 at RG1 and RG2 of the City of Grande Prairie

Sameng Inc.

5.6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-4: Rainfall Data for the Year 2015 at RG1 and RG2 of the City of Grande Prairie

Sameng Inc.

5.7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-5: Rainfall Data for the Year 2016 at RG1, RG2 and RG3 of the City of Grande Prairie

Sameng Inc.

5.8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-6: Rainfall Data for the Year 2017 at RG1, RG2 and RG3 of the City of Grande Prairie

Sameng Inc.

5.9

Storm Drainage Master Plan 2018 Final Report (Revision 1)

5.3.4

City of Grande Prairie

Recent Significant Rainfall Events

From 2013 to 2017, there were seven rainfall events that exceeded a 2-year return period according to the City rain gauges: two in 2015, three in 2016 and two in 2017. The following describes these significant rainfall events; a summary is provided in Table 5-2. Figures of the rainfall distribution for each of those events are presented in Figure 5-7 to Figure 5-13. The assigned return periods are based on the new IDF curves recommended in this Master Plan. • The June 19 to 20, 2015 rainfall moved in a northwestern direction and covered a very large area, much beyond the City limits. In Grande Prairie, the rainfall lasted 15 hours and was recorded as a 2-year 1-hour event, a 5-year 4-hour event and a 20-year 12hour event. Photos and videos found on the web shows that some roads flooded at depths of more than 30cm, including 109 Street at 89 Avenue. • The June 22, 2015 was a very intense but short duration rainfall that hit part of the City. According to radar images, the storm cell that hit the City was quite localized and not much wider than the City itself. The storm was going in a southeast direction. It was recorded as a 4-year 30-minute event at the rainfall gauge to the southeast of the City (RG2). This rainfall is said to have been accompanied with lots of lightning and a funnel cloud was spotted to the west of the City, according to online news reports. Reports of flooding in the City could not be found on the web. • The June 14 to 17, 2016 rainfall event, which unleashed a very large amount of rain over the City (60 to 80mm) and the surrounding areas over a three-day period, prompted some high stream flow advisories for parts of northwest Alberta, including the Grande Prairie area. The rainfall was never intense but was quite sustained; it was recorded as a 4 to 7-year 24-hour rainfall event at all three City gauges. Reports of flooding in the City could not be found. • The August 2, 2016 rainfall event was one for the record books. This slow northmoving band of storm cells hit the City of Grande Prairie around 6PM and unleashed an incredible amount of water over a short period. The rainfall was recorded as a 325year 1-hour event at RG3 (north) and a 75-year 1-hour event at RG2 (southeast), while RG1 (west) recorded a more modest 4-year 1-hour event which is still quite significant. This event caused substantial flooding throughout the City and many roads were flooded at large depths for hours, prompting road closures and emergency services to respond. This flood event was covered by many major newscasts and there are many videos uploaded on YouTube showing the extent of the flooding at many locations. This rainfall prompted the Government of Alberta to provide disaster relief funding to the affected residents. • The August 21 to 22, 2016 rainfall event covered a very large area and was moving in a north-eastern direction. During the peak of the event, this rainfall was recorded as an intense 2 to 5-year 1-hour event at all three gauges of the City, although it rained for a total of 26 hours. Although not as significant as the August 2nd event from 3 weeks

Sameng Inc.

5.10

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

prior, this event was still very intense and caused flooding in a few locations according to news coverage of the event and YouTube videos. â&#x20AC;˘ The May 23 to 24, 2017 rainfall covered a very large area and was moving in a northeast direction, with rainfall lasting for up to 12 hours in the City. Although not very intense, the rainfall was recorded as a 3 to 5-year 12-hour duration event. Reports of flooding in the City could not be found, but some flooding in adjacent Counties was reported in the news. â&#x20AC;˘ The September 18 to 21, 2017 rainfall resulted in more than 60 mm of water falling over the City over the course of nearly three days. Although not very intense, the rainfall was recorded as a 3 to 4-year 24-hour duration event. Reports of flooding in the City could not be found. Table 5-2: Summary of Rainfall Events Exceeding a 1:2-Year Return Period in the City of Grande Prairie from 2013 to 2017 Date June 19-20, 2015 June 22, 2015 June 14-17, 2016

August 2, 2016

August 21-22, 2016

May 23-24, 2017

September 18-21, 2017

Peak Return Period RG1: 20-yr (12-hr) RG2: 14-yr (12-hr) RG1: < 2-yr RG2: 4-yr (30-min) RG1: 5-yr (24-hr) RG2: 7-yr (24-hr) RG3: 4-yr (24-hr) RG1: 4-yr (1-hr) RG2: 75-yr (1-hr) RG3: 325-yr (1-hr) RG1: 5-yr (1-hr) RG2: 3-yr (1-hr) RG3: < 2-yr RG1: 5-yr (12-hr) RG2: 3-yr (12-hr) RG3: 4-yr (12-hr) RG1: 4-yr (24-hr) RG2: 4-yr (24-hr) RG3: 3-yr (24-hr)

Sameng Inc.

5.11

Total Rainfall Depth RG1: 65 mm RG2: 62 mm RG1: 14 mm RG2: 20 mm RG1: 66 mm RG2: 80 mm RG3: 61 mm RG1: 24 mm RG2: 51 mm RG3: 48 mm RG1: 40 mm RG2: 35 mm RG3: 37 mm RG1: 42 mm RG2: 35 mm RG3: 37 mm RG1: 61 mm RG2: 67 mm RG3: 62 mm

Total Duration 15 hours 2.5 hours 50 to 60 hours

3 to 5 hours

26 hours

11 to 12 hours

60 hours

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-7: Rainfall Data for the June 19 to 20, 2015 Rainfall Event (peak: 20-yr 12-hr event)

Figure 5-8: Rainfall Data for the June 22, 2015 Rainfall Event (peak: 4-yr 30-min event)

Sameng Inc.

5.12

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-9: Rainfall Data for the June 14 to 17, 2016 Rainfall Event (peak: 7-yr 24-hr event)

Figure 5-10: Rainfall Data for the August 2, 2016 Rainfall Event (peak: 325-yr 1-hr event)

Sameng Inc.

5.13

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-11: Rainfall Data for the August 21 to 22, 2016 Rainfall Event (peak: 5-yr 1-hr event)

Figure 5-12: Rainfall Data for the May 23 to 24, 2017 Rainfall Event (peak: 5-yr 12-hr event)

Sameng Inc.

5.14

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-13: Rainfall Data for the September 18 to 20, 2017 Rainfall Event (peak: 4-yr 24-hr event)

Sameng Inc.

5.15

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Flow Monitoring 5.4.1

Flow Monitoring Gauge Location and Data Availability

The City of Grande Prairie owns and operates four (4) flow monitoring gauges installed in storm sewers throughout the City. Table 5-3 provides a summary of the monitored locations; these locations are shown on the map of Figure 5-26. These stations operate from about May to September and are removed for the winter. The City uses Depth-Velocity sensors to measure water depths (with submerged pressure transducer) and velocities (with ultra-sonic doppler), to calculate flow rates in sewer pipes. The City operated three flow monitors from 2009 to 2012, purchased a fourth gauge in 2013, and plans to purchase another two gauges for the 2018 season. Prior to and including 2016, the gauges were installed at the same four location each year. In 2017, the location of three of the four gauges was changed. Table 5-3: Summary of City of Grande Prairie Flow Monitoring Gauges Flow Monitoring Gauge MH ID (sorted by outfall system)

MH 75001 (Outfall #1 system)

MH 54017 (Outfall #3 system)

MH 63507 (Outfall #28 system) MH 57299

Location and Description In 1500mm dia. pipe upstream (east) of MH 75001 West of 108 Street and 116 Avenue intersection in green space. Monitors flows at downstream end of the Outfall #1 basin north of the City. It is located downstream of four stormwater management facilities (#6, #7, #10, #24), but lots of the flow going through this pipe is uncontrolled. In 1400mm dia. pipe upstream (south) of MH 54017 West side of 108 Street, north of 109 Avenue in grassed area. Monitors flows at downstream end of the Outfall #3 basin servicing the area north of 100 Avenue, west of Bear Creek. It is located downstream of three of stormwater management facilities (#13, #23 and #42), but lots of flow going through this pipe is uncontrolled. In 525mm dia. pipe upstream (east) of MH 63507 92 Avenue east of 98A Street. Monitors flows at the upstream end of the Outfall #28 system in Highland Park, servicing a small residential area. Flows through this gauge are uncontrolled. In 1050mm dia. pipe upstream (north) of MH 57299 Sameng Inc.

5.16

Years of Record

2009-2016

2017

2009 2013-2016

2009

Storm Drainage Master Plan 2018 Final Report (Revision 1)

Flow Monitoring Gauge MH ID (sorted by outfall system) (Outfall #37 system)

MH 57100 (Outfall #37 system)

MH 96006 (Outfall #102 system)

MH 97003 (Outfall #151 system)

5.4.2

City of Grande Prairie

Location and Description 111 Street between 96 and 97 Avenue. Monitors flows in the northwest part of the Richmond Industrial Park area. Flows through this gauge are uncontrolled and come from the industrial development and part of 100 Avenue. In 1650mm dia. pipe upstream (west) of MH 57100 89 Avenue west of 109 Street. Monitors uncontrolled flows that comes from the western part of the Richmond Industrial area, as well as the controlled flows from the Centre West Industrial Park. In 1200mm dia. pipe upstream (north) of MH 96006 92 Street south of 92 Avenue. Monitors flows at the downstream end of the Outfall #102 system, servicing many residential neighbourhoods including Morgan Meadows, Cobblestone and Hillside. Flows through this gauge are uncontrolled. In 1000mm dia. pipe upstream (north) of MH 97003 88 Street south of 116 Avenue. Monitors flows at downstream end of southeast Crystal Lake Estates neighbourhood just before the dry pond #02 and Outfall #151. Flows through this gauge are uncontrolled, but smaller pipes downstream force the water to surge into the dry pond.

Years of Record 2011-2016

2017

2010-2017

2017

Summary of Flow Monitoring Data from 2013 to 2017

Figure 5-14 to Figure 5-18 illustrate the recorded flow monitoring data from Year 2013 to 2017 (May to October) at the City gauges. The figures show the rainfall intensity along the top, and the measured flow rate and flow depth at each gauge.

Sameng Inc.

5.17

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-14: Measured Flow Monitoring Data for the Year 2013

Sameng Inc.

5.18

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-15: Measured Flow Monitoring Data for the Year 2014

Sameng Inc.

5.19

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-16: Measured Flow Monitoring Data for the Year 2015

Sameng Inc.

5.20

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-17: Measured Flow Monitoring Data for the Year 2016

Sameng Inc.

5.21

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-18: Measured Flow Monitoring Data for the Year 2017

Sameng Inc.

5.22

Storm Drainage Master Plan 2018 Final Report (Revision 1)

5.4.3

City of Grande Prairie

Recent Significant Rainfall Runoff Events

Figure 5-19 to Figure 5-25 illustrate the recorded flow monitoring data for the seven rainfall events that exceeded a 1-in-2-year return period between 2013 and 2017, as explained in Section 5.3.4 above. Also shown on these figures is the modeled flow rate and flow depth according to the computer model; see Section 6.0 for more details on model calibration. Flow monitoring data observations are provided in Table 5-4 below. Out of these seven rainfall events, all measured pipes were surcharged during the August 2, 2016 event (325-year 1-hour event) as well as during the August 21 to 22, 2016 rainfall event (5-year 1-hour event). The sewers in the Richmond Industrial Park area exceeded their capacity and/or were surcharged both on June 22, 2015 and May 23-24, 2017, but all other monitored pipes were generally less than half full during those two events.

Sameng Inc.

5.23

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table 5-4: Summary of Flow Monitoring Data for Rainfall Event Exceeding a 1:2-Year Return Period in the City of Grande Prairie from 2013 to 2017 Date & Return Period

Observations

June 19-20, 2015 20-year 12-hour

MH 75001: Peak flow is about half of pipe capacity. Good correlation with rainfall data. MH 63507: Peak flow is about half of pipe capacity. Good correlation with rainfall data. MH 57299: Peak flow is about two-thirds of pipe capacity. Good correlation with rainfall data, although the gauge indicates sustained flows for many hours after the end of the rainfall. MH 96006: Peak flow is about two-thirds of pipe capacity. Good correlation with rainfall data.

June 22, 2015 4-year 30-minute

MH 75001: Peak flow is about one-quarter of pipe capacity. Good correlation with rainfall data. MH 63507: Peak flow is about half of pipe capacity. Good correlation with rainfall data. MH 57299: Peak flow exceeds pipe capacity. Good correlation with rainfall data, although the gauge indicates sustained flows for many hours after the end of the rainfall. MH 96006: Peak flow is about half of pipe capacity. Good correlation with rainfall data.

June 14-17, 2016 7-year 24-hour

MH 75001: Peak flow is about one-third of pipe capacity. Good correlation with rainfall data. MH 63507: Peak flow is about one-third of pipe capacity. Peak water depth is about half of pipe diameter. Good correlation with rainfall data. MH 57299: No data during peak of rainfall. MH 96006: Peak flow is about half of pipe capacity. Peak water depth is about half of pipe diameter. Good correlation with rainfall data.

August 2, 2016 325-year 1-hour

MH 75001: Peak flow is about two-thirds of pipe capacity, although the peak water depth exceeds the pipe diameter (surcharged pipe). Good correlation with rainfall data. Flow is sustained in the pipe for many hours after the rainfall, likely due to large amount of street ponding and water draining out of ponds. MH 63507: There was a gauge failure at the peak of the event. The gauge had recorded water depths in the order of 3.0m before failing; the pipe diameter is 0.525m. This large depth suggests that the downstream sewer system was extremely surcharged (to ground). MH 57299: Peak flow is about three quarters of pipe capacity, and the peak water depth was about 1.0m, such that the pipe was flowing full. Good correlation with rainfall data. Flow is sustained in the pipe for many hours after the rainfall. MH 96006: Peak flow rate seems incorrect (small) and does not match the flow depth. The water depth reached 2.2 metres, which is almost double the pipe diameter. This pipe was surcharged for about an hour. Good correlation with rainfall data.

Sameng Inc.

5.24

Storm Drainage Master Plan 2018 Final Report (Revision 1)

Date & Return Period

City of Grande Prairie

Observations

August 21-22, 2016 5-year 1-hour

MH 75001: Peak flow is about half of pipe capacity. Peak water depth exceeded the pipe diameter for nearly 2 hours (surcharged). Good correlation with rainfall data. MH 57299: Peak flow is about two-thirds of pipe capacity. Peak water depth exceeded the pipe diameter for nearly 2 hours (surcharged). Good correlation with rainfall data.

May 23-24, 2017 5-year 12-hour

MH 54017: Peak flow is about one-quarter of pipe capacity. Peak water depth is about half of pipe diameter. Good correlation with rainfall data. Flow is sustained for many hours after end of rainfall, likely due to ponds emptying. MH 57100: Peak flow is about half of pipe capacity. Peak water depth slightly exceeds pipe diameter for about an hour. Good correlation with rainfall data. Flow is sustained for many hours after end of rainfall, likely due to ponds emptying. MH 96006: Peak flow is about half of pipe capacity. Peak water depth is about one-third of pipe diameter. Good correlation with rainfall data, with the exception that the water depth (but not flow rate) increases slowly many hours after the rainfall has stopped. This may be due to backwater from the downstream Woody Channel, but it was not confirmed. MH 97003: Peak flow is about 15% of pipe capacity. Peak water depth is about one-third of pipe diameter. Good correlation with rainfall data.

September 1821, 2017 4-year 24-hour

MH 54017: Peak flow is about 20% of pipe capacity. Peak water depth is about half of pipe diameter. Good correlation with rainfall data. MH 57100: Peak flow is about one-third of pipe capacity. Peak water depth is about two-thirds of pipe diameter. Good correlation with rainfall data. MH 96006: Peak flow is about half of pipe capacity. Peak water depth is about half of pipe diameter. Good correlation with rainfall data. MH 97003: Peak flow is about 20% of pipe capacity. Peak water depth is about one-third of pipe diameter. Good correlation with rainfall data.

Sameng Inc.

5.25

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-19: Flow Monitoring Data (Measured Flow and Modeled Flow and Depth) for the June 19 to 21, 2015 Rainfall Event (peak: 20-yr 12-hr event)

Sameng Inc.

5.26

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-20: Flow Monitoring Data (Measured Flow Only â&#x20AC;&#x201C; Not Modeled) for the June 22, 2015 Rainfall Event (peak: 4-yr 30-min event)

Sameng Inc.

5.27

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-21: Flow Monitoring Data (Measured Flow and Depth Only â&#x20AC;&#x201C; Not Modeled) for the June 14 to 17, 2016 Rainfall Event (peak: 7-yr 24-hr event)

Sameng Inc.

5.28

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-22: Flow Monitoring Data (Measured Flow and Depth and Modeled Flow and Depth) for the August 2, 2016 Rainfall Event (peak: 325-yr 1-hr event)

Sameng Inc.

5.29

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-23: Flow Monitoring Data (Measured Flow and Depth Only â&#x20AC;&#x201C; Not Modeled) for the August 21 to 22, 2016 Rainfall Event (peak: 5-yr 1-hr event)

Sameng Inc.

5.30

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-24: Flow Monitoring Data (Measured Flow and Depth and Modeled Flow and Depth) for the May 23 to 24, 2017 Rainfall Event (peak: 5-yr 12-hr event)

Sameng Inc.

5.31

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Figure 5-25: Flow Monitoring Data (Measured Flow and Depth and Modeled Flow and Depth) for the September 18 to 20, 2017 Rainfall Event (peak: 4-yr 24-hr event)

Sameng Inc.

5.32

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Recommended Rainfall and Flow Monitoring Program A memo describing the recommended rainfall and flow monitoring program for the City of Grande Prairie was issued on March 26, 2018. The memo is attached as Appendix B of this report. Figure 5-27 illustrates the proposed rainfall and flow monitoring gauge locations. The key purposes of monitoring rainfall and storm runoff flows are to provide a better understanding of the relationship between rainfall and runoff. This would then extend to provide information for calibrating the computer simulation models used to evaluate and design storm infrastructure in the City. Several factors influence how runoff are derived from rainfall events. Having measured data to calibrate the computer models provides for improved confidence on system assessment results. The recommended monitoring program is summarized as follows: • Maintain the three current rain gauge locations (RG1, RG2 and RG3) and add two additional rain gauges at the following locations: (1) The Ivy Lake maintenance building to the northeast of the City; (2) the Eastlink Centre Knowledge Campus southwest of the City. These locations have been selected to maintain even spacing between gauges, and where City facilities exist. • Six (6) storm sewer flow monitoring locations were identified. These locations were selected based on the expected usefulness of the data in calibrating the model, as well as to characterize the storm runoff characteristics of different land use types. • Two (2) locations for water quality measurements were identified. They coincide with the flow monitoring locations. The first location is upstream of the Canfor Ditch in Richmond Industrial Park on 89 Avenue, west of 109 Street; the second is downstream of the highway commercial area at 116 Avenue, west of 102 Street. Additional Recommendations Additional rainfall and flow monitoring data recommendations are: • Quality Assurance and Data Verification: Validate rainfall and flow monitoring data on an ongoing basis to ensure that the collected data is precise and accurate. For example, data from the rainfall gauges can be manually verified with a graduated cylinder gauge. Furthermore, erroneous data, such as during the gauge installation and removal, should be deleted. • Flow Monitoring Gauge Calibration: The storm sewer flow monitoring gauges should be calibrated and regularly verified during periods of low flow (small rainfall). Their installation should also be checked regularly to ensure they remain clean and in place, especially following intense rainfalls. A staff gauge can be used to verify the high-water mark recorded by the gauge. • Weather Radar Station: The City may consider future rainfall monitoring to include weather radar installations. This technology has improved in its operational simplicity and is becoming more economical, such that some municipalities (i.e. Edmonton) have

Sameng Inc.

5.33

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

started operating their own stations for local observations with greater refinement. Weather radars can also be used for weather forecasting and emergency preparedness situations.

Sameng Inc.

5.34

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE STORM PIPE (BASIN BY COLOUR) WATERCOURSE / WATERBODIES STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE

132 AVENUE

AR BE

TWP RD 720

RAIN GAUGE AND FLOW MONITOR LEGEND

INT

K EE

RAIN GAUGE

INT

100 STREET

INT

INT INT

INT

INT INT

INT

INT INT

MH 75001 2009-2016

RG3

FLOW MONITOR

CRYSTAL LAKE

INT

IN/OUTLET

RAIN GAUGE CATCHMENT DIVIDE

INT

MH 97003 2017

INT IN/OUTLET

IN/OUTLET

INT INT

INT

C AR BE

116 AVENUE

INT

EK RE

INT

MH 54017 2017

INT

108 AVENUE RESERVOIR 10.97

12.19

IN/OUTLET

INT

MH 63507 2009, 2013-2016 500 CMP 1980 16.50 0.00

MH 96006 2010-2017

INT

MH 57100 2017

RGE RD 54

INT

RG1

84 STREET

100 AVENUE

INT

92 STREET

100 AVENUE

INT

108 STREET

116 STREET

WOOD LAKE

Prepared By:

INT

124 STREET

84 AVENUE

RG2

INT

OUR RES

INT

INT INT

INT

INT INT

x2 x2

R CES

INT

INT INT INT

INT

OAD

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

INT

Client:

INT INT

INT

INT INT

INT

INT INT

68 AVENUE

INT

INT INT

FLYINGSHOT LAKE

INT

CR E

Project:

AKE

Storm Drainage Master Plan 2018

INT

IEN L O'BR

RGE RD 65

INT

MH 57299 2009, 2011-2016

INT INT

Title: IN/OUTLET

Historical and Existing Rainfall and Flow Monitoring Gauge Locations

Scale:

Figure:

1:40,000

5-26

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE STORM PIPE (BASIN BY COLOUR) WATERCOURSE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE

132 AVENUE

A BE

TWP RD 720

INT

EE CR

RAIN GAUGE AND FLOW MONITOR LEGEND INT

INT

RAIN GAUGE

INT

100 STREET

INT

INT INT

INT

INT INT

INT

RG3

FLOW MONITOR INT

INT

IN/OUTLET

RAIN GAUGE CATCHMENT DIVIDE

CRYSTAL LAKE

INT

IN/OUTLET

MH 80004

IN/OUTLET INT INT

INT

AR BE

116 AVENUE

INT

K EE

CR INT

INT

108 AVENUE RESERVOIR

RG5 10.97

12.19

IN/OUTLET

INT

INT INT

INT

100 AVENUE

500 CMP 1980 16.50 0.00

MH 63198 INT

RGE RD 54

INT

RG1

84 STREET

INT

92 STREET

100 AVENUE

INT

MH 57100 108 STREET

116 STREET

WOOD LAKE

RG2

Prepared By:

INT

124 STREET

INT

84 AVENUE

INT

O RES

INT

INT INT

INT

MH 56136 INT

x2 x2

E URC

INT INT INT

INT

AD S RO

INT

RG 4

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

MH 52003 INT

Client:

INT INT

INT

INT INT

68 AVENUE

INT

INT INT

INT

FLYINGSHOT LAKE

INT

Project:

CR E

AKE

IEN L

Storm Drainage Master Plan 2018

INT

O'BR

RGE RD 65

MH 57204

INT INT

Title: IN/OUTLET

Proposed Rainfall and Flow Monitoring Gauge Locations for 2018 Monitoring Season

Scale:

Figure:

1:40,000

5-27

Storm Drainage Master Plan 2018 Final Report (Revision 1)

6.0

City of Grande Prairie

Computer Hydraulic Model Development Previous Computer Modeling Efforts

The Cityâ&#x20AC;&#x2122;s storm drainage computer model consists of 25 individual XPSWMM models. Each model represents the sewer system for a different part of the City. Some models cover many neighbourhoods, others small areas. These models only include storm sewer pipes; they do not include the major drainage system. As a result, these models cannot properly assess the performance of the existing drainage system under intense rainfall events. The models also do not allow for any flow transfer from one basin to the other, either through the piped system, or via the ground surface. Lastly, these models are independent; if there needs to be a change in parameter that affects every model, all 25 models will have to be updated accordingly. This can be very time-consuming and is prone to inducing manual errors. Computer Modeling Overview For this storm drainage master plan update, the entire Cityâ&#x20AC;&#x2122;s drainage infrastructure was combined into a single Mike Urban hydraulic model (provided to City â&#x20AC;&#x201C; see Appendix G). It includes storm pipes, manholes, outfalls, ditches, drainage channels, stormwater management facilities, orifices, weirs, and more. The computer model also includes a major drainage system component, including roads and other major drainage paths. Furthermore, the model was constructed such that the interactions between the minor system and the major system were fully-integrated. For example, the rainfall runoff on the ground surface must enter the sewer system at the catchbasin locations. Furthermore, if the pipe is surcharged and has no more capacity, the runoff will not be allowed in the sewer system and will consequently pool on the ground surface and/or overflow to the next sag location, as it would naturally. The resulting computer model provides a good representation of the existing major and minor drainage system interactions, and the modeling results provide a good understanding of the surface flows, surface ponding locations and depths, as well as drainage system constraints. We trust that the model provides accurate and realistic hydraulic results for this planning level of study. For future design phases, this model could be updated to include more details. This comprehensive dual-drainage hydraulic model was used to evaluate the performance of the existing drainage system under many rainfall events. The results are presented in Section 7.0. It was also used to develop improvement recommendations to the existing drainage system, explained in Section 8.0. The following summarizes how the various component of the model were constructed.

Sameng Inc.

6.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Selection of Computer Model Software A variety of computer modeling software are marketed as being able to complete dualdrainage and/or 2D modeling of stormwater systems. The following summarizes some wellknown software. • XPSWMM by Innovyze is a fully dynamic hydraulic and hydrologic modelling software that combines 1D calculations for upstream to downstream flow with 2D overland flow calculations. Its use over the last 25 years, as well as its UK Environment Agency benchmark testing and U.S. FEMA approval, has made it one of the most stable and well-used simulation software programs in the world. XPSWMM is currently the preferred modeling software by the City of Grande Prairie. (http://www.innovyze.com/products/xpswmm/) • PCSWMM by CHI is an advanced modeling software for stormwater, wastewater, watershed and water distribution systems. Their software is marketed as being able to help improve new water supply, drainage and green infrastructure design, floodplain delineation, sewer overflow mitigation, water quality and integrated catchment analysis, 1D-2D modeling and more. (https://www.pcswmm.com/) • MIKE URBAN by DHI is an urban water modelling software that covers all water networks in the city, including water distribution systems, storm water drainage systems, and sewer collection in separate and combined systems. This software is marketed as being the model of choice when important parameters for model selection are stability, workflow, openness, flexibility, GIS integration and physical soundness. All collection system (CS) modules are based on DHI’s MOUSE, MIKE 1D or SWMM engines with unrivalled numerical stability and efficiency. Mike Urban is the model of choice by the City of Edmonton. (https://www.mikepoweredbydhi.com/products/mikeurban) • SWMHYMO by J.F. Sabourin and Associates Inc. is a complex hydrologic model used for the simulation and management of stormwater runoff in either small or large rural and urban area. Using easily acquired watershed or sewershed information, SWMHYMO processes rainfall records to simulate the transformation of rainfall into surface runoff. Computed hydrographs can be routed through pipes, channels or stormwater control ponds and reservoirs. In urban area, the effective capture rates of catch basins and the effects of storage in street low points can also be simulated. (www.jfsa.com/hydrologic-modelling-swmhymo.php) For this project, it was decided to use DHI’s Mike Urban (Release 2017 SP1). The main reasons for using Mike Urban are that Sameng is very experienced with its interface, capabilities and limitations, it is known to be very stable (instability is often an issue with dual-drainage system), and we know that it can produce accurate results. Although another software may have generated similar results, the risks of potentially constructing a dualdrainage model that was unstable and produced erroneous results was not justified. The Mike Urban database can be exported to SWMM format and vice versa.

Sameng Inc.

6.2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

The use of Mike Urban for this project proved successful. The model is stable, the modeling results are similar to measured flows and depths (see Section 6.7 for model calibration) and it produces ponding results that are similar to those observed throughout the City during intense rainfall events. Although Mike Urban was used for this project, developers should not be mandated to use Mike Urban to model their drainage systems. Nevertheless, their model must be stable and produce truthful results. Network Model 6.4.1

Minor Drainage System

The sewer/piped system was constructed by importing all elements from the City’s geodatabase, and then completing the network by adding missing pipes and manholes, missing/incorrect information (e.g. diameter, invert, length, etc.), and by inferring how data gaps would be filled (e.g. record drawings, previous models, discussions with City, assumed/estimated, etc.). The network model does not include abandoned or removed sewer elements, and it does not include individual catchbasins and catchbasin leads (these were omitted to keep the model simple, although they could be added in a future revision or for detailed design projects). Some pipes/manholes on private properties were included if the information was available. Most of the key culverts are included in the model, but majority of the local property access culverts were purposely excluded. The size of most of these culverts had to be assumed or estimated, as the City’s geodatabase does not include culvert information. Information for major culverts along important major drainage channels (e.g. Woody Channel and Canfor Ditch) were inserted according to as-builts, design drawings or supplemental information provided by the City. Inlet and outlet head losses were assumed/identified for each culvert. Head loss parameters were added to each manholes, tees, inlets, outlets, outfalls and pipes. Head losses at manholes are very important and must not be ignored, especially when evaluating the drainage system under surcharged conditions. Head losses can exceed more than 0.5 m at some manholes, which is significant. For pipes, the Manning’s friction parameter was attributed based the pipe material. For PVC and concrete pipes, a Manning’s ‘n’ of 0.013 was utilized. For CSP pipes, an ‘n’ of 0.024 was used. Major drainage channels and important ditches were included in the model, such as the Woody Channel and the Canfor Ditch amongst many others. Cross sections and elevation for these channels were based on LiDAR information, and/or on record drawings. Manning’s ‘n’ for these channels was often assumed as 0.03. The resulting minor drainage network, including stormwater management facilities, is illustrated in Figure 6-1.

Sameng Inc.

6.3

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

6.4.2 Major Drainage System A major drainage ‘surface’ layer was constructed to provide a 1-D representation of the overland drainage system. This includes roadways, ditches, swales, and overflow locations. The alleys were not included in the major drainage model unless they formed an important part of the major drainage system; alleys could be added in a future model revision to future refine the modeling results, and to identify flood risks in alleys. The LiDAR elevation data was used to assign elevations to the major drainage system. The major drainage system was constructed to include nearly all the City roads, with nodes spaced about 40 metres apart, to provide a sufficiently detailed topography to the major drainage network. Where necessary, additional nodes were inserted at high and low points along a road, especially in areas prone to flooding. In some areas, runoff conveyance is done via roadside ditches. Generally, the roadside ditches were included as part of the road cross-section. The geometry of the roads was assigned as open channels with cross-sections representing typical City road cross-sections. All local residential roads were assigned the same crosssection, for simplicity. Additional flow paths were traced into the model along some of the walkways, green spaces, and alleys to complete the overland network. These were generally done manually and on a case by case basis to ensure that flood risks due to surface ponding were well identified. Typical cross-sections were attributed to each of them. For some private developments, such as large commercial sites, a major drainage network was included in the model to estimate the potential flood risks on the site. However, in most instances, flood risks on large private developments were not modeled, since we did not have the sewer system information for these sites, and also because the City is mostly concerned about flood risks caused by drainage issues on public properties and roadways. The resulting major drainage network is illustrated in Figure 6-2. 6.4.3

Major – Minor System Integration

The major drainage system nodes were connected to the storm sewer system’s manholes (or catchbasin manholes) where catchbasins are physically connected/located using ‘orifice’ elements that approximate flows between the surface and the receiving manhole. The orifices were sized as to not significantly overestimate or underestimate actual catchbasin capacities, while keeping the model simple. This means that the capacity of the modeled catchbasins may be different than what actually exists. At this planning level, this methodology was deemed sufficient to identify major drainage issues. It should be noted that the catchbasin capacity was generally not the limiting factor for runoff conveyance; the pipes were.

Sameng Inc.

6.4

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

6.4.4 Stormwater Management Facilities and Control Structures All known stormwater management facilities and their control structure (i.e. orifice and/or weir) were included in the model. The ponds were generally modeled as open channels with cross-sections that approximate the depth-storage characteristics of the ponds they represent. These stage-storage curves were developed based on LiDAR elevation contours and from as-built information where available. These curves are presented in Appendix C. The storm sewer system is connected to stormwater management facilities through their inlet and outlet pipes. Major drainage connections to the ponds, including pond overflows and major drainage inflows, were also modeled. For wet ponds, a normal water level was included as a boundary condition, such that each simulation starts with the normal ‘dead’ storage of the ponds already filled. The depth and dead storage of wet ponds was often assumed, but this had no impact on the hydraulic results. Many of the ponds in the model were constructed using a combination of channels constructed in a “star” shape. The sole purpose of that layout was for the creation of the 2dimensional ponding maps. The performance of the ponds is not affected by this layout. Control structures, including orifices and weirs, were added to the model through a review of record drawings. The City does not currently have a database of this type of infrastructure. The model does not include storage facilities on private developments (e.g. below-ground storage). This is because the City does not have a database of these private storage facilities and we are therefore unaware of their existence. This may result in areas improperly identified to be at flood risk. For the next model revision, the City should identify such areas where private site storage exists, and these storage devices should be added to the model. 6.4.5

Outfalls in Receiving Waterbodies/watercourses

Some of the receiving waterbodies and watercourses, such as Bear Creek, the Woody Channel south of 68 Avenue and Flyingshot Lake were not included in this model, and outfalls to these bodies were modeled as ‘free outfalls’. This means that flood potential from these waterbodies/watercourses, including backwater effects, were not accounted for in the model. We do not believe that this model simplification has any significant impact on the simulation results.

Sameng Inc.

6.5

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Runoff Model Storm catchments were created for the entire City. With the assistance of a GIS software and LiDAR elevation map, drainage basins were delineated and connected to their tributary surface node. This model includes a total of about 9,040 catchment areas throughout the City, with a median size of 0.23 ha. The flow length and slope of each catchment area was calculated from the LiDAR data. Each catchment area was then assigned an imperviousness value using an overlay of existing land-use maps, based on imperviousness values identified in Table 12.3 of the City of Grande Prairie design manual. For instance, 10% for parks, 50% for single-family residential, 70% for industrial and 90% for commercial. For catchment areas covering multiple land-use zones, the percent imperviousness is based on the proportional area in each zone. In large undeveloped areas, the imperviousness was manually modified (reduced) as to not overestimate the runoff potential for the site. Imperviousness values used in various part of the City is illustrated in Figure 6-3. The individual catchment areas are connected to their tributary surface node, and not directly into the sewer system. As such, the runoff from these catchments must first flow onto the surface before entering the storm sewer system via the ‘orifices’ that represent catchbasins. This provides a more realistic approach to modeling. To calculate the runoff generation, the Kinematic Wave method was used with typical Horton Infiltration parameters. These parameters are summarized in Table 6-1 below. Table 6-1: Kinematic Wave Parameters (Horton Parameters) for Storm Catchments Impervious Component

Pervious Component

Flat

Medium

Wetting

0.050 mm

Storage

0.625 mm

2.5 mm

Initial Losses

Horton’s Infiltration Capacity Maximum

75.6 mm/hr

Minimum

7.56 mm/hr

Horton’s Exponent Wet Condition

5.4 /hr

Dry Condition

0.036 /hr

Manning’s Number Manning’s Number

Sameng Inc.

(n = 0.017)

(n = 0.03)

6.6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

The following Table 6-2 demonstrates the approximate runoff coefficient of storm catchments of various imperviousness and for various rainfall events. As shown in the table, the runoff coefficient of areas with low imperviousness (e.g. 10%) varies significantly depending on the rainfall event. For high intensity rainfalls, most of the rainfall is converted to runoff as the pervious soil cannot absorb all the water. For areas with already large imperviousness values (e.g. 90%), the runoff coefficient does not vary greatly. It should be noted that these are average runoff coefficient during the entire duration of the rainfall event. For the very large rainfall intensity rainfalls, the runoff coefficient at the peak of the rainfall event will be about 0.95 regardless of the site imperviousness. During the very low intensity rainfall events, the runoff coefficient is similar to the imperviousness. Table 6-2: Approximate Runoff Coefficient for Catchment Areas of Various Imperviousness Runoff Coefficient Imperviousness

5-year 4-hour Chicago Dist.

100-year 4-hour Chicago Dist.

5-year 24-hour Chicago Dist.

100-year 24-hour Chicago Dist.

0.20

0.47

0.23

0.38

0.55

0.70

0.57

0.65

0.89

0.93

0.90

0.92

31.31 mm

58.67 mm

52.47 mm

97.51 mm

10% (Park) 50% (Single-Family Residential) 90% (Commercial) Total Rainfall Depth

Summary of Physical Model Elements The final model contains: • Nodes: 15,560 (about 5,200 belong to the sewer system and culverts, the others represent the major drainage system, drainage channels and stormwater management facilities. • Links: 16,600 (about 5,200 belong to the sewer system and culverts, the others represent the major drainage system, drainage channels and stormwater management facilities. • Orifices: 3,070 (18 are control structure orifices, the others represent catchbasin connections) • Weirs: 13 (all are control structure weirs) • Catchments: 9,044

Sameng Inc.

6.7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Model Calibration and Validation 6.7.1

Overview

To validate the modeling results, actual measured rainfalls from the City rainfall gauges were used to simulated historical events. The rainfall data for the nearest rainfall gauge was attributed to the catchment. The modeling results were then compared with actual flow and depth measurements collected by the flow monitoring gauges. The model parameters were calibrated as needed. The four following rainfall events were used for calibration purposes: • June 19-21, 2015: A 20-year return period, 12-hour duration rainfall event. • August 2, 2016: A 325-year return period, 1-hour duration rainfall event. • May 23-24, 2017: A 5-year return period, 12-hour duration rainfall event. • September 18-20, 2017: A 4-year return period, 48-hour duration rainfall event. These events were selected for calibration purposes due to their large return period. Large return periods were chosen because the main purpose of the model is to determine the hydraulic performance of the system under large and intense rainfall events, and to identify flood risks accordingly. 6.7.2

Calibration / Validation Results

The calibration results and measured flow monitoring data for the above four rainfall events are illustrated in Figure 5-19, Figure 5-22, Figure 5-24 and Figure 5-25 of this report. See Figure 5-26 for gauge location. The following summarizes the outcome of the model calibration and validation process at each gauge locations. In general, the model is in agreeance with the flow monitoring data, with some exception. The modeled flows, volume and water depth are often higher than the measured flows, especially at the peak of the rainfall. Minor refinements to the model parameters were made following the calibration, to further improve on the model’s accuracy. MH 75001 (1500mm pipe) • Modeled Events: June 19, 2015; August 2, 2016 • The modeled flows at this location were generally higher than the measured flows by 25 to 100% during both calibration events. The modeled depth was about 50% greater than the measured depth (on August 2, 2016). Furthermore, the total modeled volume was between 65% and 75% larger than the total measured volume. • The shape and response of the modelled vs. measured flows and water levels is very similar. During the June 10, 2015 event, the flow rate increased and dropped at virtually the same time. On August 2, 2016, the flows and water level were sustained high much past the peak of the rainfall and both dropped about 3 hours after the peak of the rainfall.

Sameng Inc.

6.8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

• These differences in flow rate and water depth are not well-understood, but it may be associated with (1) site imperviousness are smaller than modeled; (2) greater infiltration rate than modeled; (3) the model does not account for ditch storage and large depression storage which may exist in those areas; (4) the actual rainfall in the basin was not as intense as recorded; and/or (5) flow measurement errors. Additional flow monitoring in this large basin is recommended to identify the reasons for the discrepancies. • The model parameters were not adjusted as the differences in flow between the model and the measured data are reasonable. The model may be overconservative on the runoff and flow rate, but additional investigations and modeling would be needed to confirm. MH 54017 (1400mm pipe) • Modeled Events: May 23, 2017; September 18, 2017 • The modeled flows at this location were very similar to the measured flows, typically within 25% from one another during both calibration events. However, the modeled depth was often about 50 to 100% greater than the measured depth. Upon review of the modeling results, it was found that the model returns a higher water depth due to the head losses applied to the manhole during high flows. The total modeled volume was between 15% and 30% larger than the total measured volume. • The shape and response of the modelled vs. measured flows and water levels is very similar. During the May 24, 2017 rainfall, both measured and modeled flows were sustained at similar rates for nearly 24 hours after the rainfall had stopped, likely due to the ponds emptying. Similar flow rates were recorded during the September 18, 2017 event. • This correlation between the model and the measured data suggest that the model parameters in this commercial and residential area are reasonable. Head losses may be slightly exaggerated, but conservative. MH 63507 (525mm pipe) • Modeled Events: June 19, 2015; August 2, 2016 • For the June 19, 2015 rainfall, the modeled flows at this location were generally very similar to the measured flows throughout the duration of the rainfall, typically within 25% from one another. The total modeled volume was about 10% greater than the measured volume. The model suggest that this pipe was very surcharged during that event. The shape and response of the modelled vs. measured flows and water levels is also very similar. • For the extreme August 2, 2016 rainfall, the flow monitoring gauge recorded a rapid rise in flow rate and depth. The gauge failed shortly after the pipe surcharged. The modeled flows also show the quick rise in water level and flow rate, and it suggests that the flows but especially the water level in the sewer system were sustained high Sameng Inc.

6.9

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

for many hours (about 7 hours for the water level) after the rainfall stopped. The model suggest that this pipe was very surcharged during that event. This correlates to flooding observed in this system. • This correlation between the model and the measured data suggest that the model parameters in this residential area are reasonable. MH 57299 (1050mm pipe) • Modeled Events: June 19, 2015; August 2, 2016 • For the June 19, 2015 rainfall, the modeled flows at this location were up to 200% smaller than the measured flows, except for the peak flow rate which was very similar. The model suggests that the water depth in the pipe is sustained for many hours after the rainfall has passed, but that the flow is negligible indicating a backwater condition. The measured data shows sustained flows for many hours after the rainfall has passed. It is hypothesized that the measured flows are incorrect as the water in the pipe is backwater due to large flows downstream of this pipe, not active flow. • For the extreme August 2, 2016 rainfall, the modeled flows were generally slightly higher than the measured flows, except for the peak flow rate which was the same. The total modeled volume was 25% larger than the measured volume. The water level was also modeled as being higher than the measured flow, but it was all backwater (no flow) according to the model results. It should be noted that the velocity gauge failed during this event, but flows were strangely still reported. The shape and response of the modelled vs. measured flows and water levels is very similar. • It was decided not to update the model parameters for this industrial area, mostly since the peak flows matches quite well, and the measured data is questionable. MH 57100 (1650mm pipe) • Modeled Events: May 23, 2017; September 18, 2017 • The modeled flows at this location were up to 40% larger than the measured flow. The modeled water depths were generally 30 to 100% larger. The modeled volume was 70 to 80% larger. • An interesting observation for this gauge is the velocity on May 23, 2017. At the peak of the rainfall and flow event, the velocity at this gauge suddenly dropped from 2.2 m/s to 1.0 m/s for about 3 hours, and then back up to 2.3 L/s, gradually slowing down for the next several hours. At the same time as this sudden drop in velocity, the water level kept rising and surcharged the pipe. This suggests that there a flow restriction downstream (e.g. culverts in Canfor Ditch?) that reduced the capacity of the pipe. A similar phenomenon was observed at the peak of the rainfall on September 19, 2017. • Although the flows and water depths were quite different, the shape and response of the modelled vs. measured flows and water levels during both calibration events is very similar.

Sameng Inc.

6.10

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

• During the May 24, 2017 rainfall, both measured and modeled flows were sustained at similar rates for nearly 24 hours after the rainfall had stopped, likely due to the ponds emptying. Similar flow rates were recorded during the September 18, 2017 event. • These differences in flow rate and water depth is not well-understood, but it may be associated with (1) the model includes large undeveloped areas to the west of 116 Street that may not actually contribute much runoff (yet) at this gauge; (2) the Central West Business Park is modeled as releasing some of its flow uncontrolled into the Richmond Industrial Park system, but an orifice likely exists (however, there is no documentation showing an orifice); (3) site imperviousness are smaller than modeled; (4) greater infiltration rate than modeled (most of the yards are gravel, but are assumed as highly impervious in the computer model); (5) the model does not account for potentially large local storage depressions or poor lot grading which may exist in the industrial lots; (6) the actual rainfall in the basin was not as intense as recorded; and/or (7) flow measurement errors. Additional flow monitoring in this large basin is recommended to identify the reasons for the discrepancies. • Since the calibration was completed, the imperviousness of the undeveloped areas west of 116 Street was reduced to represented undeveloped conditions, and additional depressional storage was added to these areas as to not overestimate runoff. The above discussions do not consider these updates to the model. In all likelihood, the model is still overestimating runoff compared to measured flows. MH 96006 (1200mm pipe) • Modeled Events: June 19, 2015; August 2, 2016; May 23, 2017; September 18, 2017 • The August 2, 2016 measured data is incorrect (gauge failure) and was not discussed/compared below. • The modeled flows at this location were up to 200% larger than the measured flow during the peak of the rainfall, but they were often within 25% for the rest of the rainfall event. The modeled water depths were almost identical to the measured ones during the September 18, 2017 event. The modeled volume was 10 to 50% larger for all three calibration events. • Although the flows and water depths were quite different at the peak of the event, the shape and response of the modelled vs. measured flows and water levels during both calibration events is very similar. • The large difference in peak flow is quite unusual and may suggest (1) that the runoff is actually rerouted to another system when the flows are too high; (2) there is something controlling the upstream peak flows that is not in the model; or (3) the soils are more pervious than originally anticipated. This could not be confirmed. Of note, this pipe is interconnected via a 900mm pipe to another pipe at this MH 96006 when the flows are high, but the gauge measures flow upstream of the interconnection and this should not have an impact on the measured flows.

Sameng Inc.

6.11

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

• It was decided not to update the model parameters for this area given the general agreeance between the model results and the measured data. Additional flow monitoring and sewer investigations in this complex basin is recommended to identify the reasons for the discrepancies between the modeled and measured peak flows. The model might be missing an important piece of infrastructure such as the interconnection to another system, a flow restrictor, etc. MH 97003 (1000mm pipe) • Modeled Events: May 23, 2017; September 18, 2017 • The modeled flows at this location were up to 100% larger than the measured flow during the peak of the rainfall, but they were often within 25% for the rest of the rainfall event. For the September 18, 2017 event, the modeled and measured flows were almost identical (except for the peaks). The modeled volume was 20% to 30% larger. The modeled water depth was generally higher than the measured ones, likely due to large manhole head losses introduced by the model during large flow conditions. • Although the flows and water depths were quite different at the peak of the event, the shape and response of the modelled vs. measured flows and water levels during both calibration events is very similar. • It was decided not to update the model parameters for this mostly residential area given the generally agreeance between the model results and the measured data.

Sameng Inc.

6.12

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE STORM SEWER PIPE CULVERT DRAINAGE CHANNEL, DITCH STORMWATER MANAGEMENT FACILITY

TWP RD 720

100 STREET

132 AVENUE

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

AD S RO

E URC

O RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

O'BR

IEN L

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Minor Drainage System Modeling Schematic Scale:

Figure:

1:40,000

6-1

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE ROADWAY CULVERT DRAINAGE CHANNEL, DITCH STORMWATER MANAGEMENT FACILITY MAJOR DRAINAGE FLOW PATH AND OVERFLOW PATH

TWP RD 720

100 STREET

132 AVENUE

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

AD S RO

E URC

O RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

O'BR

IEN L

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Major Drainage System Modeling Schematic Scale:

Figure:

1:40,000

6-2

LEGEND

148 AVENUE CITY BOUNDARY PROPERTY LINE WATERCOURSE / WATERBODY STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE

132 AVENUE

TWP RD 720

IMPERVIOUSNESS

CR K EE

100 STREET

90 - 100% 80 - 89% 70 - 79% CRYSTAL LAKE

60 - 69% 50 - 59%

A BE

40 - 49%

116 AVENUE

30 - 39%

RE EK

20 - 29% 10 - 19% 0 - 9%

108 AVENUE RESERVOIR

100 AVENUE

108 STREET

116 STREET

124 STREET

84 AVENUE

RGE RD 54

84 STREET

WOOD LAKE

Prepared By:

URC

O RES OAD

ES R

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

LAKE

Project:

Storm Drainage Master Plan 2018

IEN O'BR

CR E

FLYINGSHOT LAKE

RGE RD 65

92 STREET

100 AVENUE

Title:

Storm Catchment Imperviousness Modeling Schematic

Scale:

Figure:

1:40,000

6-3

Storm Drainage Master Plan 2018 Final Report (Revision 1)

7.0

City of Grande Prairie

Existing Drainage System Assessment Simulation Results

7.1.1

Overview of Simulation Result Figures

The existing drainage system of the City of Grande Prairie was evaluated under various design rainfall events, using the computer model as explained in Section 6.0. Simulation results for the 5-year 4-hour Chicago distribution rainfall event, the 100-year 4-hour Chicago distribution rainfall event and the 100-year 24-hour Chicago distribution rainfall event (proposed design rainfalls as presented in Section 3.2.4) are included in this section. 7.1.2

Minor Drainage System

For the storm sewer system, the simulation results show the theoretical loading of the pipes (Qpeak/Qcap) as well as the surcharge depth in each pipe (identified at the manholes). From these results, it is possible to identify which sewer pipes are flowing beyond their pipefull capacity (Qpeak/Qcap > 1.0), and how surcharged the pipes are. 7.1.3

Major Drainage System

For the major drainage system, the simulation results show the ponding depth and extents along the main drainage paths, as well as the peak flow rate on the ground surface. The maximum ponding elevations calculated at individual nodes by the model were interpolated over the entire developed portion of the City. This interpolated water elevation map was then superimposed on the LiDAR ground elevation map to create 2D ponding maps that show the maximum ponding depths and extents. The 2D ponding maps are very useful as they estimate the extent of the ponding areas on public and private properties, and they can consequently be used to identify flood risk areas. However, these 2D ponding maps are subject to interpretation from the computer modelers, and the accuracy of the results varies by area depending on many factors. Therefore, these 2D ponding maps shall not be assumed to be 100% correct, but they are very useful to identify areas at higher risk of flooding.

Sameng Inc.

7.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Flood Risk Assessment Following a thorough review of the modeling results, the approximate flood risks in various parts of the City during a 100-year rainfall event were identified and are presented in Figure 7-1. The flood risk categories shown on that figure are explained in Table 7-1 below. It should be clarified that these are flood risks associated with surface flooding, not sewer backups. Areas identified to be at a higher risk of flooding are further assessed in Section 7.5. Table 7-1: Flood Risk Quantification Table Flood Risk Category

Flood Risk Description Many properties are at risk of flooding during a 100-year (or smaller) rainfall event.

High Flood Risk

A high flood risk was attributed to areas where flooding of many vehicles, properties and residences/buildings is expected during the 100-year rainfall event, based on a thorough review of the 2D ponding maps. These are often areas with a poor major drainage system, depressions with large ponding depths, and/or poor private lot grading. Properties may be at risk of flooding during a 100-year (or smaller) rainfall event.

Medium Flood Risk

A medium flood risk was attributed to areas where there is potential for some vehicles, properties and residences/buildings to be flooded, and/or for which the flooding may pose safety concerns. This includes all areas: -

Adjacent to a depression with ponding depths exceeding 50cm.

Adjacent to a depression with ponding depths exceeding 35cm AND for which the ponding appears to overflow onto private properties.

Few properties are at risk of flooding during a 100-year rainfall event. Any flood risk would be very localized. Low/No Flood Risk

A low/no flood risk was attributed to areas that were not classified as being medium or high risk. Generally, these areas: -

Are well-graded with a good major drainage system.

Are not adjacent to a large/deep ponding area (less than 35cm ponding depth).

Sameng Inc.

7.2

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE WATERCOURSE / WATERBODY STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE HIGH FLOOD RISK MEDIUM FLOOD RISK

132 AVENUE

A BE

TWP RD 720 x2

R INT

INT

EE CR INT

INT

100 STREET

INT

INT INT

INT

INT INT

INT

CRYSTAL LAKE

INT

INT INT

INT

375 10.06 INT INT

INT

375 10.06

INT

375 10.06

AR BE

375 10.06

116 AVENUE

INT

250

CR K EE

300 1987

INT

750 CSP 1969 12.20 0.64

150 PVC 1996 250 PVC 1996

INT

300 CONC 1969 10.96

2.00

300 CONC 1969 16.53 9.86

300 PVC

300 CONC 1969 7.23 3.87

1981

INT

108 AVENUE 300

RESERVOIR

300 STL

27.50

10.97

12.19

INT

15.00 AUGERED

INT

INT INT

INT

200 22.56

100 AVENUE

INT

300 CMP 1996 22.70 3.00

300 CSP 1996 17.00 2.00

375 1979 24.70 0.00 ABDN LINE (1992)

375 1955 44.20 0.30 (ABDN)

600 CONC 1955 78.90 0.15 (ABDN 1993)

600 1955 79.60 0.15 (ABDN 1993)

500 CMP 1980 16.50 0.00

300 CSP 1985 24.00 1.00

INT

RGE RD 54

450 1969 35.97 0.24 (ABANDONED)

450 1969 22.25 0.24 (ABANDONED)

84 STREET

92 STREET

450 1969 13.41 0.24 (ABANDONED)

108 STREET

1.11

84 AVENUE

WOOD LAKE

Prepared By:

300

INT

116 STREET

13.72

INT

124 STREET

300

INT

O RES

INT

INT INT

INT

x2 x2

E URC

INT INT INT

INT

375 CSP 1979 47.55 2.00

AD S RO

INT

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

INT

Client:

INT INT

INT

INT INT

68 AVENUE

INT

INT INT

INT

FLYINGSHOT LAKE

INT

Project:

CR E

AKE

IEN L

Storm Drainage Master Plan 2018

INT

O'BR

RGE RD 65

INT

INT INT

Title:

Flood Risk Areas in City of Grande Prairie Due to 100 Year Rainfall Scale:

Figure:

1:40,000

7-1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Stormwater Management Facility Performance The following Table 7-2 summarizes the projected water level in the ponds under existing conditions and improved conditions (see Section 8.0 for existing system improvements) according to the computer model. Results and discussions of the pond performance are summarized in the following sections. It should be noted that the Mountview pond is the only pond that may flood adjacent properties because of high water levels. The overflow of all other ponds does not appear to pose a flood risk to adjacent properties, as the overflow elevation is lower than adjacent buildings and residences.

Sameng Inc.

7.4

Table 7-2 Modeling Results of Stormwater Management Facilities Depth above NWL (Wet Pond) / Bottom (Dry Pond) Pond ID

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15* 16 17 18* 19 20 21 22 23 24 25 26 27 30 31 33 34 36 37 38 40 41 42 43* 44 46 47 48 49

Name

Ivy Lake Crystal Lake Estates / Woodgrove Country Club West Mountview Four Winds Scenic Ridge Royal Oaks Country Side South Pinnacle Ridge Crystal Village Resources and 68th Resources and 76th Westgate East Crystal Lake Fire Hall Crystal Ridge FF1 Crystal Ridge FF2 Muskoseepi Park Fish Pond Community Knowledge Campus Crystal Lake Estates South Bear Creek Westpointe at 84th Avenue Westgate West Northridge Residential (East) Northridge Residential (West) O'Brien Lake Pinnacle West Crystal Landing Woody Channel Signature Falls Centre West #1 Albinati Forebay Stoneridge #2 Grande Banks Vision West Kensington Royal Oaks North Grande Prairie Regional Hospital Trader Ridge O'Brien Lake West #1 Arbour Hills I #1 Arbour Hills I #2 Arbour Hills II Fieldbrook

Type

Wet Pond Dry Pond Dry Pond Dry Pond Dry Pond Dry Pond Dry Pond Wet Pond Wet Pond Dry Pond Wetland Wet Pond Wet Pond Wetland Wet Pond Foreflow Bay Foreflow Bay Wet Pond Dry Pond Wetland Dry Pond Dry Pond Dry Pond

5yr - 4h

0.39 1.78 1.32 2.26 1.34 1.12 0.87 0.40 0.63 0.71 0.71 0.69 0.58 0.13 -

*Note: These ponds are not modeled. SWMF Overflows. Building Flooding due to high SWMF water level.

0.80 0.63 -

1.73 1.87 2.03 1.99 3.45 1.57 1.07 0.31 1.53 0.99 2.40 1.90 2.84 0.65 2.78 0.90 2.10 2.63 1.82 1.73 -

0.50 1.37 1.23 0.78 2.42

1.10 2.55 2.30 2.47 1.58 1.18 1.50 0.72 1.30 1.19 0.38 1.30 1.21 0.19

0.80 0.63

1.64 1.17 1.91 1.73 2.76 1.49 0.52 0.25 1.34 0.85 2.27 1.61 2.68 0.65 2.65 0.80 2.07 2.49 1.72 1.40 -

0.21 1.37 0.99 0.18 1.14

Improved 100yr - 4h

1.09 2.73 2.45 2.82 1.65 1.19 1.66 0.82 1.77 1.21 1.21 1.44 1.77 0.27

0.80 0.63

1.03 0.50 0.92 1.13 1.83 0.97 0.41 0.11 0.61 0.49 1.56 0.64 1.92 0.37 2.28 0.26 1.35 0.60 1.19 0.46 -

100yr -24h

0.76 2.55 2.30 2.78 1.58 1.18 1.57 0.72 1.30 1.20 1.20 1.30 1.21 0.19

0.73 0.62

Dry Pond Wet Pond Wet Pond Wetland Wet Pond Wet Pond Dry Pond Foreflow Bay Wet Pond Wet Pond Dry Pond Dry Pond Wet Pond Wet Pond Wet Pond Wet Pond Wet Pond Wet Pond Wet Pond Wet Pond

100yr - 4h

1.64 1.17 1.91 1.73 2.76 1.48 0.52 0.25 1.34 0.85 2.20 1.60 2.06 0.65 2.65 0.80 2.07 2.49 1.72 1.40 -

0.64 1.45 1.30 0.97 2.60

0.50 1.37 1.23 0.78 2.39

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Simulation Result Description 7.4.1

5-year 4-hour Chicago Distribution Rainfall Event

Simulation results for the 5-year 4-hour design rainfall event are presented in Figure 7-2 (sewer surcharge), Figure 7-3 (theoretical loading in pipe), Figure 7-4 (surface ponding and extents) and Figure 7-5 (surface flow). MINOR DRAINAGE SYSTEM RESULTS The City of Grande Prairieâ&#x20AC;&#x2122;s current design standard is for the storm sewer system to convey the 5-year rainfall event peak flows within pipefull flow which is typical of most Alberta municipalities. However, earlier City design standards only required sewers to be designed to convey the 2-year rainfall events peak flows. Therefore, sewers in older neighbourhoods are often undersized according to current design standards. Furthermore, as discussed earlier in this report, it is recommended for the 5-year design storm event to be modified such that the proposed 5-year event would have a higher intensity than the current 5-year event; in other words, all sewers of the City are likely undersized to convey the proposed 5year event within pipefull flow. Figure 7-2 shows that many storm sewers in the City will surcharge during the 5-year event, especially in the older neighbourhoods. About 2,850 manholes (56%) will be surcharged to 1.0m below ground or less, and more than 1,000 manholes (20%) will be surcharged to grade. Figure 7-3 shows that several pipes will see flows exceeding their pipefull capacity, which correlates with the widespread surcharge experienced in the sewer system. About 98 km of pipe (39%) will see peak flows exceed their pipefull capacity, and close to 15 km of pipe (6%) will flow at more than twice their capacity. There are too many areas with sewer capacity issues during the 5-year event to list them; the problem is quite widespread and does not only affect the older neighbourhoods, but also many newer subdivisions. It should be noted that upgrading pipes with a large theoretical loading (Qp/Qc) may reduce surcharge in the system, but the solution is often more complex than that. The focus should be on ensuring that the areas do not flood and that major drainage flows can be conveyed safety. MAJOR DRAINAGE SYSTEM RESULTS Figure 7-4 shows that surface ponding during the 5-year event is not of concern for most areas, with ponding depths at street depressions rarely exceeding 35cm (only 1.3% of the modelâ&#x20AC;&#x2122;s surface road nodes have more than 35cm of ponding). Figure 7-5 shows that surface flows are also typically quite small on most roads, as the sewer system captures most of the runoff. About 3% of the roads will see surface flows exceed 500 L/s, with only 0.2% that will experience flows larger than 2,000 L/s.

Sameng Inc.

7.6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

FLOOD RISK AREAS Areas at higher flood risks due to excessive surface ponding during the 5-year 4-hour design event are (they are explained in further details in Section 7.5): 1- Richmond Industrial Park: Lack of sewer capacity throughout the industrial area with significant surcharge throughout. Major drainage overflows towards the many depressions, especially on 89 Avenue, west of 108 Street. The area has a poor major drainage system. 2- Highland Park: Lack of sewer capacity in the area with significant major drainage flows pooling at large surface depressions with inadequate major drainage overflow. 3- Avondale: Significant surface flows in the area due to major lack of capacity in the sewer system, and also significant major drainage flows coming from the north (116 Avenue). 4- Northridge: Significant surface flows coming from the ditch-serviced area to the north into large depressions. Local sewers are quite surcharged. The major drainage system is inadequate. 5- Mountview: Significant east-to-west surface runoff due to lack of sewer capacity. The SWMF is overflowing. The SWMF has no adequate major drainage overflow path. 6- Smith: Significant surface flows coming from the north and into the residential subdivision. Local sewers and downstream trunks are quite surcharged. 7- Crystal Heights: Lack of sewer capacity at the upstream end of the storm system. Excess surface flows accumulate at local depressions. Most stormwater management facilities appear capable of storing the flows from the 5-year 4-hour design rainfall event without exceeding their capacity, with the exception of the following ponds: SWMF #5 (Four Winds) and #6 (Scenic Ridge).

Sameng Inc.

7.7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

7.4.2

City of Grande Prairie

100-year 4-hour Chicago Distribution Rainfall Event

Simulation results for the 100-year 4-hour design rainfall event are presented in Figure 7-6 (sewer surcharge), Figure 7-7 (theoretical loading in pipe), Figure 7-8 (surface ponding and extents) and Figure 7-9 (surface flow). MINOR DRAINAGE SYSTEM RESULTS Sewer pipes during an intense 100-year 4-hour event are expected to be flowing full and be surcharged to grade in most locations, as shown in Figure 7-6. About 4,050 manholes (81%) will be surcharged to 1.0m below ground or less, and close to 2,300 manholes (46%) will be surcharged to grade. Figure 7-7 shows that several pipes will see flows exceeding their pipefull capacity during this event, which is expected. About 121 km of pipe (48%) will see peak flows exceed their pipefull capacity, and close to 23 km of pipe (9%) will flow at more than twice their capacity. MAJOR DRAINAGE SYSTEM RESULTS Figure 7-8 shows that surface ponding during the 100-year event is widespread, but some areas, especially local depressions with poor major drainage overflow, are at an enhanced risk of flooding. Ponding depths exceeded 35cm at 670 surface road nodes (9% of the entire model road nodes), which is quite substantial. Figure 7-9 shows that surface flows are quite significant on many roads, as the sewer pipes cannot convey these large runoff flows. About 26% of the roads will see surface flows exceed 500 L/s, with nearly 4% of them experiencing flows larger than 2,000 L/s. FLOOD RISK AREAS Areas at high flood risks due to excessive surface ponding during the 100-year 4-hour design event are the same as for the 5-year event, but the flood risks are even greater. Most stormwater management facilities appear capable of storing the flows from the 100year 4-hour design rainfall event without exceeding their capacity, with the exception of the following ponds: SWMF #4 (Mountview), SWMF #5 (Four Winds), #6 (Scenic Ridge), #10 (Crystal Village), #33 (Centre West #1), #38 (Vision West), # 40 (Kensington) and #41 (Royal Oaks North).

Sameng Inc.

7.8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

7.4.3

City of Grande Prairie

100-year 24-hour Chicago Distribution Rainfall Event

Simulation results for the 100-year 24-hour design rainfall event are presented in Figure 7-10 (sewer surcharge), Figure 7-11 (theoretical loading in pipe), Figure 7-12 (surface ponding and extents) and Figure 7-13 (surface flow). Since this event is an extension of the 100-year 4-hour event, the flood risks should be similar or worse. MINOR DRAINAGE SYSTEM RESULTS Sewer pipes during an intense 100-year 24-hour event are expected to be flowing full and be surcharged to grade in most locations, as shown in Figure 7-10. About 4,000 manholes (80%) will be surcharged to 1.0m below ground or less, and close to 2,350 manholes (47%) will be surcharged to grade. Figure 7-11 shows that several pipes will see flows exceeding their pipefull capacity during this event, which is expected. About 117 km of pipe (46%) will see peak flows exceed their pipefull capacity, and close to 22 km of pipe (9%) will flow at more than twice their capacity. MAJOR DRAINAGE SYSTEM RESULTS Figure 7-12 shows that surface ponding during the 100-year event is widespread, but some areas, especially local depressions with poor major drainage overflow, are at an enhanced risk of flooding. Ponding depths exceeded 35cm at 720 surface road nodes (10% of the entire model road nodes), which is quite substantial. Figure 7-13 shows that surface flows are quite significant on many roads, as the sewer pipes cannot convey these large runoff flows. About 24% of the roads will see surface flows exceed 500 L/s, with nearly 4% of them experiencing flows larger than 2,000 L/s. FLOOD RISK AREAS Areas at high flood risks due to excessive surface ponding during the 100-year 24-hour design event are almost identical as the ones at risk during the 100-year 4-hour event. Water levels in the ponds during the 100-year 24-hour event are generally higher than during the 100-year 4-hour event. Most stormwater management facilities appear capable of storing the flows from the 100-year 24-hour design rainfall event without exceeding their capacity, with the exception of the following ponds: SWMF #4 (Mountview), SWMF #5 (Four Winds), #6 (Scenic Ridge), #10 (Crystal Village), #22 (Westpointe at 84th Avenue), #23 (Westgate West), #33 (Centre West #1), #38 (Vision West), # 40 (Kensington), #41 (Royal Oaks North) and #49 (Fieldbrook).

Sameng Inc.

7.9

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Detailed Assessment of High Flood Risk Areas Many high flood risk areas grouped into 11 distinct locations were identified throughout the City of Grande Prairie, as shown in Figure 7-1. These locations are (in no particular order): 12- Northridge (southeast) – Residential / Commercial 13- Avondale / Montrose – Mostly Residential 14- Highland Park – Residential / Commercial 15- Mountview (west) and Crystal Ridge (southwest) – Residential 16- Crystal Heights and Ivy Lake Estates – Residential 17- Smith / Hillside (southeast) – Residential / Industrial 18- Patterson Place (southwest) – Residential 19- Country Club Estates – Residential 20- Richmond Industrial / College Park (southwest) – Industrial / Commercial 21- Gateway (south) – Commercial 22- Northgate (north) / Albinati Industrial – Industrial The flood mechanisms and flooding extents for these high flood risk areas are summarized in Appendix D. The main flooding mechanism in these areas is often associated with a poor major drainage system. Improvement concepts to mitigate flood risks in these areas are summarized in Section 8.0.

Sameng Inc.

7.10

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

SURCHARGE DEPTH â&#x2030;¥ 1.0m BELOW GROUND 0.5 TO 1.0m BELOW GROUND 0.0 TO 0.5m BELOW GROUND

TWP RD 720

132 AVENUE

0.0 TO 0.5m ABOVE GROUND

100 STREET

> 0.5m ABOVE GROUND

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

OAD

R CES OUR RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN L

O'BR

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:5-year 4-hour Event - Sewer Surcharge

Scale:

Figure:

1:40,000

7-2

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

THEORETICAL LOADING Qp / Qc â&#x2030;¤ 0.5 0.51 - 1.0

TWP RD 720

1.01 - 1.5

132 AVENUE

1.51 - 2.0

100 STREET

> 2.0

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

OAD

R CES OUR RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN L

O'BR

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:5-year 4-hour Event - Theoretical Loading in Pipe

Scale:

Figure:

1:40,000

7-3

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

SURFACE PONDING DEPTHS <0.15m 0.16m - 0.35m

TWP RD 720

0.36m - 0.50m

132 AVENUE

0.51m - 1.00m

100 STREET

>1.00m

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

AD S RO

E URC

O RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

O'BR

IEN L

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:5-year 4-hour Event - Surface Ponding

Scale:

Figure:

1:40,000

7-4

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

PEAK SURFACE FLOW RATE 0 - 250 L/s 251 - 500 L/s

TWP RD 720

501 - 1000 L/s

132 AVENUE

1001 - 2000 L/s

100 STREET

> 2000 L/s

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

OAD

R CES OUR RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN L

O'BR

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:5-year 4-hour Event - Peak Surface Flow Rate

Scale:

Figure:

1:40,000

7-5

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

SURCHARGE DEPTH â&#x2030;¥ 1.0m BELOW GROUND 0.5 TO 1.0m BELOW GROUND 0.0 TO 0.5m BELOW GROUND

TWP RD 720

132 AVENUE

0.0 TO 0.5m ABOVE GROUND

100 STREET

> 0.5m ABOVE GROUND

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

AD S RO

E URC

O RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

O'BR

IEN L

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:100-year 4-hour Event - Sewer Surcharge

Scale:

Figure:

1:40,000

7-6

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

THEORETICAL LOADING Qp / Qc â&#x2030;¤ 0.5 0.51 - 1.0

TWP RD 720

1.01 - 1.5

132 AVENUE

1.51 - 2.0

100 STREET

> 2.0

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

AD S RO

E URC

O RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

O'BR

IEN L

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:100-year 4-hour Event - Theoretical Loading in Pipe

Scale:

Figure:

1:40,000

7-7

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

SURFACE PONDING DEPTHS <0.15m 0.16m - 0.35m

TWP RD 720

0.36m - 0.50m

132 AVENUE

0.51m - 1.00m

100 STREET

>1.00m

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

AD S RO

E URC

O RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

O'BR

IEN L

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:100-year 4-hour Event - Surface Ponding

Scale:

Figure:

1:40,000

7-8

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

PEAK SURFACE FLOW RATE 0 - 250 L/s 251 - 500 L/s

TWP RD 720

501 - 1000 L/s

132 AVENUE

1001 - 2000 L/s

100 STREET

> 2000 L/s

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

OAD

R CES OUR RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN L

O'BR

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:100-year 4-hour Event - Peak Surface Flow Rate

Scale:

Figure:

1:40,000

7-9

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

SURCHARGE DEPTH â&#x2030;¥ 1.0m BELOW GROUND 0.5 TO 1.0m BELOW GROUND 0.0 TO 0.5m BELOW GROUND

TWP RD 720

132 AVENUE

0.0 TO 0.5m ABOVE GROUND

100 STREET

> 0.5m ABOVE GROUND

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

OAD

R CES OUR RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN L

O'BR

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:100-year 24-hour Event - Sewer Surcharge

Scale:

Figure:

1:40,000

7-10

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

THEORETICAL LOADING Qp / Qc â&#x2030;¤ 0.5 0.51 - 1.0

TWP RD 720

1.01 - 1.5

132 AVENUE

1.51 - 2.0

100 STREET

> 2.0

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

CES

OUR

RES

RGE RD 65

92 STREET

100 AVENUE

ROA

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN O'BR

LAKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:100-year 24-hour Event - Theoretical Loading in Pipe Scale:

Figure:

1:40,000

7-11

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

SURFACE PONDING DEPTHS <0.15m 0.16m - 0.35m

TWP RD 720

0.36m - 0.50m

132 AVENUE

0.51m - 1.00m

100 STREET

>1.00m

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

AD S RO

E URC

O RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

O'BR

IEN L

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:100-year 24-hour Event - Surface Ponding

Scale:

Figure:

1:40,000

7-12

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

PEAK SURFACE FLOW RATE 0 - 250 L/s 251 - 500 L/s

TWP RD 720

501 - 1000 L/s

132 AVENUE

1001 - 2000 L/s

100 STREET

> 2000 L/s

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

OAD

R CES OUR RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN L

O'BR

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Existing System 1:100-year 24-hour Event - Peak Surface Flow Rate

Scale:

Figure:

1:40,000

7-13

Storm Drainage Master Plan 2018 Final Report (Revision 1)

8.0

City of Grande Prairie

Improvement Concept Plans for Existing Drainage System Overview

Drainage improvements were conceptualized for developed areas of the City that are at a higher risk of flooding, with a goal to provide them with a 100-year level of flood protection. The following describes these concepts, which areas they benefit, and estimated costs. All improvement concepts are illustrated on Figure 8-1. It should be noted that a reduced level of flood protection (say 25-year or 50-year) could also be provided for these areas by reducing the amount of work required, but the target level of flood protection of the following improvements was to significantly reduce flood risks during the 100-year design rainfall event. Simulation results showing the impact of the proposed improvements on the storm drainage system during a 100-year 4-hour design rainfall event are presented in Figure 8-11 (sewer surcharge), Figure 8-12 (theoretical loading in pipe), Figure 8-13 (surface ponding and extents) and Figure 8-14 (surface flow). Review of 2013 Storm Drainage Master Plan Recommendations The 2013 Storm Drainage Master Plan provided a number of recommendations to reduce flood risks for the area. The following lists these improvements and explains whether these upgrades will have an impact on flood risk reduction. The estimate cost of these improvements was $2.82M. 1. Replace existing 1500 CMP to increase capacity. Reduce surcharge in trunk and surface ponding in upstream areas - $750,000 a. This improvement is also recommended in Section 8.3.1 below. However, it should be noted that this 1500mm pipe capacity increase is not enough to significantly reduce flood risks in the area. The simulation results from the previous master plan only shows marginal benefit for the area, suggesting that more upgrades are required to achieve a 100-year level of flood protection for the area. 2. Divert 100 Street at 132 Avenue to the west into future Northgate / Arbour Hills system. Reduce flooding and surcharging of 100 Street trunk. - $140,000 a. This improvement has merit given that the 100 Street storm trunk has capacity issues. This option should be reviewed with the developers in the area and may require ponds and pipes to be oversized. The cost estimate for this option seems low. b. We do not believe that this improvement will prevent having to implement the improvement presented in Section 8.3.1 below, but it may achieve a higher level of flood protection.

Sameng Inc.

8.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

3. Replace outfall on 105 Avenue and sewer on 100 Street from 110 Avenue to 105 Avenue to increase capacity. Reduce surface ponding and surcharging in upstream system - $1,200,000 a. This outfall was recently upgraded, but the sewer on 100 Street was not yet upgraded. Although this improvement would reduce flood risks for the area, it would not be sufficient to provide a 100-year level of flood protection. The improvement presented in Section 8.3.2 will achieve the necessary level of flood protection. 4. Surge pond in park space in Highland Park. Reduce surcharging and intercept major system flows - $100,000 a. Constructing a surge pond in the park space would provide very little benefit to the most at-risk areas which are further northwest. Nevertheless, a surge pond could further protect the adjacent school, but it would also negatively impact the existing sport fields. The costs of that upgrade seem low, and its benefits for the area are questionable. The area already overflows into the Woody Channel with little flood risks to the area. 5. Upgrade capacity of 900 CSP upstream of outfall. Reduce surcharging in trunk and upstream surface ponding - $250,000 a. This area is not subject to significant flood risks and no improvements are recommended in this Master Plan. The major drainage system in this area is acceptable. The need and benefit of this improvement is questionable, as it would not be sufficient to prevent street ponding and major drainage overflows in the area. It might reduce the frequency of the ponding events. 6. Upgrade capacity of 900 CSP Country Club Outfall. Reduce surcharging in trunk and upstream surface ponding - $310,000 a. Upgrading this outfall would provide little benefit to the most at-risk area of the neighbourhood which is further northeast on Poplar Drive. The simulation results in the previous master plan suggest that the benefits are negligible. Instead, a more robust option should be implemented to reduce flood risks at this location. See Location 8 of Appendix D for details. 7. Surge pond in park space in Cobblestone. Reduce surcharging and intercept major system flows - $70,000 a. Our modeling results do not show any major drainage issues in this area. The benefits of this improvement are questionable. The major drainage system in the area appears adequate. The costs of that upgrade seem low. To summarize, most of the recommended improvements in the previous master plan provide very little benefit for the area, and the flood risks are not expected to reduce significantly during the very intense rainfall events. The improvements appeared to focus on small sewer system upgrades that would provide the greatest benefit at the lowest cost. However, these

Sameng Inc.

8.2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

improvements would not actually provide a 100-year level of flood protection for the area. Furthermore, since the previous master plan did not model the surface drainage flows, many areas considered at-risk of flooding in this master plan were not identified in the previous master plan. Improvement Concepts by Area 8.3.1

Northridge Area (North-Central)

OVERVIEW This improvement, illustrated in Figure 8-2, has the objective to reduce flood risks for the following Location and Areas listed in Appendix D: • Location 1 – Northridge (southeast), Area A, B, C & D • Location 2 – Avondale / Montrose, Area A, B & C • Location 4 – Mountview (west) and Crystal Ridge (southwest), Area A & B The main improvement concept is to capture and convey major drainage flows from this area, and to reduce the hydraulic grade line in the existing sewer pipes at strategic locations by installing large diameter pipes and conveying this drainage in an upgraded conveyance channel (ditch) south of 116 Avenue. DETAILS Upgrading the ditch south of 116 Avenue is necessary to provide significant benefit to Location 1, 2 and 4. This includes the lowering and widening of the ditch, the upgrade of culvert crossings, and the upgrade to the downstream pipe, which may require the construction of a new overflow outfall near the existing outfall #1. The 100-year peak flows in that ditch are estimated at 20,000 L/s. Location 1 receives a significant amount of major drainage flows during the 100-year rainfall event and has a poor major drainage system such that water is retained in the many large depressions. Through computer modeling, it was found that improving the existing major drainage overflow ditch (north-to-south ditch going from 124 Avenue to 117 Avenue) may not be sufficient to provide a 100-year level of flood protection due to the physical constraints (i.e. too narrow, not able to be much deeper as there is already sanitary pipe in that alignment). Consequently, the main improvement concept for this area is to collect and convey the 100-year major drainage flows (estimated at 7,000 L/s) to the 116 Street ditch using 1500mm to 2100mm pipes installed along 102 Street. Large grates would need to be installed on the roads to capture these large surface flows. Unfortunately, this concept is not cost-benefiting. Although they may not provide a 100-year level of flood protection for the entire area, some of the most cost-benefiting upgrades to benefit Location 1 are:

Sameng Inc.

8.3

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

• Interconnect the existing 2100mm storm sewer on 116 Avenue at the 102 Street intersection to the upgraded 116 Avenue ditch. Also interconnect the 1800mm/2100mm pipe further upstream to the upgraded ditch at 100 Street as well as between 100 Street and 102 Street. These will reduce the hydraulic grade line in the existing storm sewers servicing this area and increase conveyance capacity in the system, which should reduce flood risks. • Install a large grate(s) on 116 Avenue at the 102 Street intersection and improve overflow into the 116 Avenue ditch to reduce ponding at that intersection (Area D) and reduce major drainage flows going towards Location 2. • Improve the existing north-south ditch (from 124 Avenue to 117 Avenue) as much as possible to reduce ponding depths/extent in Area A and B. Regrade roads and upgrade culverts as needed. Location 2 significantly benefits from the capture of major drainage flows along 116 Avenue via the installation of a larger grate(s) connected to the existing 2100mm pipe on 116 Avenue, and major drainage overflows into the 116 Avenue ditch. Even with preventing all major drainage flows from flowing south of 116 Avenue and into Location 2, additional improvements are needed to provide a 100-year level of flood protection in Location 2 (see Section 8.3.2 below). Location 4 benefits from the proposed 1800mm pipe along 116 Avenue from just east of the railroad to 100 Street. At the railroad, this pipe would capture drainage from the swale north of 116 Avenue (via inlet) and prevent that drainage from overflowing the road and flowing south towards Area B, thus reducing flood risks in Area A and B. It would also interconnect with the existing storm system at the railroad, thus reducing the hydraulic gradeline in these systems and increasing the conveyance capacity, hence reducing flood risks. Additional improvements will still be needed to provide a 100-year level of flood protection in Location 4, Area B (see Section 8.3.2 below). 8.3.2

Avondale / Montrose Area (North-Central)

OVERVIEW This improvement, illustrated in Figure 8-3, has the objective to reduce flood risks for the following Location and Areas listed in Appendix D: • Location 2 – Avondale / Montrose, Area A, B & C • Location 4 – Mountview (west) and Crystal Ridge (southwest), Area B The main improvement concept is to capture and convey major drainage flows and reduce the hydraulic grade line in the existing sewer pipes at strategic locations by installing large diameter pipes and conveying this drainage to Bear Creek.

Sameng Inc.

8.4

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

DETAILS Location 2 is at risk of flooding due to large major drainage flows and very low conveyance capacity in the existing sewer system, combined with many localized depressions and a lack of proper major drainage overflow. Although this area will significantly benefit from the proposed improvements presented in Section 8.3.1 above, more improvements are needed to offer a 100-year level of flood protection. A 1500mm to 2100mm pipe is recommended to be installed on 108 Avenue with large grates installed at each intersection to prevent major drainage flows from flooding areas south of 108 Avenue. Furthermore, this large pipe would be also interconnected with the existing storm pipes along the way, hence reducing the hydraulic grade line in the existing storm sewers servicing this area and increase conveyance capacity in the system, which should reduce flood risks. The existing outfall would also need to be upgraded. To further reduce flood risks in Area A, the existing major drainage overflow path should be improved, and some roads regraded to reduce the amount of major drainage flow reaching this high flood risk area. As an alternative option, the existing conveyance pipe could also be upgraded to a 900mm pipe. Location 4 is at risk of flooding because the existing stormwater management facility in Mountview is too small and overflows, flooding the surrounding area. This is still an issue even after constructing the improvement explained in Section 8.3.1 above. The railroad blocks the major drainage flows out of the area, and it cannot be regraded. There is also very limited space for pond expansion in the area. Therefore, the water should be piped out to reduce flood risks. The concept is to install a 1050mm to 1500mm pipe from the existing pond to the proposed 1500mm pipe on 108 Avenue, while adding large capture grates on the street to reduce major drainage flows into the existing pond. However, the cost-benefit of this pipe is debatable. As an alternative, there may be an option to construct a pond overflow pipe across the railroad and let the water overflow onto 99 Street, which could then be captured by the proposed 108 Avenue storm pipe via a large grate. It should be noted that this may increase flood risks in Area C of Location 2. This alternative option could be reviewed at the next design stage. As another option, constructing another surge pond near the existing pond would reduce flood risks. However, upgrades to the storm sewer system may still be necessary. This alternative option was not modeled.

Sameng Inc.

8.5

Storm Drainage Master Plan 2018 Final Report (Revision 1)

8.3.3

City of Grande Prairie

Highland Park / Swanavon Area (Central)

OVERVIEW This improvement, illustrated in Figure 8-4, has the objective to reduce flood risks for the following Location and Areas listed in Appendix D: • Location 3 – Highland Park, Area A, B, C, D The main improvement concept is to capture and convey major drainage flows from the two large depressions and to reduce the hydraulic grade line in the existing sewer pipes at strategic locations by installing large diameter pipes and conveying this drainage to Bear Creek. DETAILS Location 3 is at risk of flooding because of the large volume of major drainage overflow reaching the areas, and because this area (Area A and B) is lower than the ground elevation of the downstream sewer system, resulting in water backing up into these depressions during extreme rainfall events. Since there is very little space available to construct a surge pond in the area, and since improving the major drainage overflow will be very challenging (due to topography), it is recommended to convey this excess flow directly into Bear Creek via a large diameter pipe. A 1500mm to 1800mm pipe is recommended to be constructed from the Area A and B depressions to a new outfall in Bear Creek, interconnecting to the existing storm pipes along the way to reduce the hydraulic gradeline in the existing sewers, and consequently increase their flow capacity. A 900mm pipe should be constructed to the Area C depression on 94 Avenue and connect to the proposed 1800mm pipe to reduce flood risks in that area. This improvement should also reduce major drainage overflows reaching Area D and consequently reduce ponding depths and flood risks in the area. 8.3.4

Ivy Lake / Cobblestone / Smith Area (Central-East)

OVERVIEW This improvement, illustrated in Figure 8-5, has the objective to reduce flood risks for the following Location and Areas listed in Appendix D: • Location 6 – Smith / Hillside, Area A, B, C The main improvement concept is to prevent major drainage flows from entering the Smith neighbourhood, to reduce ponding and surcharge in the very surcharged sewer system via a relief pipe to the Ivy Lake Estates Pond, and to improve the downstream conveyance channels/ditches to Woody Channel. DETAILS Location 6 is at risk of flooding because of the large volume of major drainage overflow reaching the area from 100 Avenue and 92 Street. It is recommended to regrade some of

Sameng Inc.

8.6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

the roads and walkways in Smith to prevent this major drainage overflow from entering the local roads of the neighbourhood and instead keep this major drainage overflow on the main roads which are well graded. Furthermore, a storm sewer relief pipe with a large capture grate should be installed from the 100 Avenue and 92 Street intersection (interconnecting to the existing 1050mm pipe) to the Ivy Lake Estates Pond. This will reduce the major drainage flows and ponding depths in the area, thus reducing flood risks for the area. In the industrial area south of Smith, the ditches and culverts should be upgraded all the way to the Woody Channel to reduce flood risks for the industrial areas. 8.3.5

Richmond Industrial Area (Central-West)

OVERVIEW Providing a 100-year level of flood protection for the Richmond Industrial area will be very challenging and costly. Many improvement concepts were developed and modeled as part of this study, and many solutions were found to be ineffective. Nevertheless, a total of five improvement concepts and alternatives were developed for the area and can provide a 100year level of flood protection for most of the area; each with their own challenges and constraints. Many more alternatives could also be conceptualized. These improvements are illustrated in Figure 8-6 to Figure 8-10 and have for objective to reduce flood risks in Location 9, Area A, B, C, D, & E listed in Appendix D. The main improvement concept is to convey the 100-year rainfall runoff flows from the Richmond Industrial area to the Canfor Ditch without posing any flood risks to the area during a 100-year event. DETAILS For all options, it is necessary for the existing and future industrial subdivisions west of 116 Street to minimize their peak runoff flows in the Richmond Industrial area, given the major drainage issues in Richmond Industrial. This shall be done through stormwater management facilities and control structures. This control is especially important during intense rainfall events. The City might even want to consider Real-Time Control to allow zero-release from these upstream areas during the very intense storm, and only allow release once the sewer system has regained its capacity. Area A of Location 9 floods because of the very large volume of major drainage flows reaching the area, and the poor major drainage overflow downstream (railroad ditch has capacity limitations). -

All five options suggest that major drainage has to be improved from the 95 Avenue and 113 Street bend into the railroad ditch (e.g. ditch or pipe). This would require regrading on private properties. As an alternative, the pipe could be upgraded, but that might not be possible due to shallow depths.

Sameng Inc.

8.7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

From there Option 1 and 2 suggest conveying this flow east along the tracks by upgrading the railroad ditches (but upgrading the ditch may not be possible due to physical constraints). Some berms would need to be constructed to prevent the ditch from overflowing onto private properties.

Option 3 suggests conveying this flow south via a ditch/pond expansion (or large pipe) to the proposed Richmond Pond further south.

Option 4 recommends that the flows be conveyed across the railroad and then east on 89 Avenue to overflow onto 89 Avenue, which is well graded to the east. This excess drainage would then have to be collected at Area E.

Area B of Location 9 floods because of the very large volume of major drainage flows reaching the area, and the poor major drainage overflow (108 Street is very high; most of the area west of 108 Street will be flooded by the time 108 Street overflows). -

Option 1, 3 and 4 would see the railroad ditches connected to an upgraded 1500mm pipe on 108 Street and flowing into a surge pond (17,000 m3) that would be constructed just south of the railroad. This surge pond would also interconnect to the existing 1200mm pipe just west (109 Street alignment). The surge pond would release the flows back into the existing system to the south via the existing small pipes, thus buffering the peak flows. The depression on 108 Street north of the railroad would have a large grate to capture the major drainage flows.

Option 2 is an alternative to the pond and could be combined with other options. It would see the railroad ditches connected to an upgraded 1200mm pipe north of the railroad and to a 2100mm pipe constructed on 108 Street from the railroad to 89 Avenue. The large diameter pipe on 108 Street is necessary to convey all major drainage flows from the area. There may be concerns with the cover depth of the pipe along 108 Street. This option also does not buffer the peak flows, which would require the outfalls and culverts in the Canfor Ditch to be upgraded significantly.

Area C of Location 9 may be at risk of flooding due to the large major drainage flows coming from the west of 108 Street, and due to poor major drainage from the area. -

For all options, major drainage from this industrial area into the railroad ditch, as well as the railroad ditch itself, should be upgraded to reduce the risk of flooding in this area. A major drainage easement does not appear to exist. This area is believed to have underground storage tanks; these were not included in the model.

Area D of Location 9 floods because of the very large volume of major drainage flows reaching the area, and the poor major drainage overflow east on 89 Avenue. The currently proposed Richmond Pond will reduce the flood risks in the area, but it will not provide a 100year level of flood protection. -

It is recommended that a large grate be installed on 89 Avenue near 112 Street to reduce ponding depths at this location.

Sameng Inc.

8.8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

The Richmond Pond should be connected to the existing 1200mm pipe on 84 Avenue via a 1200mm pipe constructed along the property line to the southeast. This is necessary to release some of the drainage from the pond into this pipe which has some excess capacity. If this connection is not done, the pond will overflow during the 100-year (or smaller) rainfall events and pose flood risks to many properties adjacent to the pond. The anticipated benefits of the following two improvements for Area D depend on this connection upgrade.

The inlet pipe connecting the new grate on 89 Avenue near 112 Street and the existing 1200mm/1650mm pipes to the Richmond pond should be upsized to a 2100mm diameter pipe from the currently proposed 1200mm pipe design to ensure that this area does not flood.

The Richmond Pond pipe crossing 111A Street should be upsized to a 1500mm pipe from the currently proposed 900mm pipe. This is to ensure that the water can efficiently go from the northwest side of the road to the southeast without overflowing. This is only needed if the pond is connected to the 89 Avenue storm sewer (see above).

Area E of Location 9 floods during rainfall events as small as the 5-year event, mainly because of the very large volume of major drainage flows reaching this large depression, the lack of adequate major drainage overflow across 108 Street (108 Street is very high), as well as flow restrictions in the downstream Canfor Ditch. -

For all options, the culverts in the Canfor ditch need to be upgraded to at least 3m span by 2.4m rise box culverts (4.8m span by 2.4m rise for Option 2), which will significantly increase their capacity and significantly reduce flood risks for Area E. The culvert upgrades are necessary, or else Area E will continue to flood.

For all options, the existing twin pipe outfall to the Canfor Ditch would need to be upgraded. It is recommended to upgrade the existing 1050mm pipe to a 2400mm pipe. However, if the Canfor ditch and culverts are lowered (say by 1 metre), it might be possible to upgrade this pipe to a smaller size. There may be significant challenges in upgrading these outfall pipes as they are constructed on the Canfor site.

The outfall at the downstream end of the Canfor Ditch is also recommended to be upgraded, to maintain water levels in the ditch low and reduce flood risks upstream. However, there may be a possibility to avoid having to upgrade the outfall if a stormwater management facility is constructed immediately upstream of that outfall. Benefits

8.4.1

Overview

The main benefit for the above improvements is flood mitigation. The main goal is to reduce flooding to private properties and vehicles due to excessive surface ponding. One of the

Sameng Inc.

8.9

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

secondary goals is to prevent flooding to private properties due to sewer backups (sanitary sewers); surface ponding can be a large contributor of manhole inflow in the sanitary sewers. Surface ponding can damage both private and public properties. This damage includes flooding of property on the street and on private lots (e.g. vehicles, garages), basement flooding (e.g. seepage through doors, walls, and window wells), and flooding of the main floor of homes. Typically, street ponding depths more than 35cm can flood vehicles. The estimated flood damage cost to the average Grande Prairie home is $50,000 for basement floods, and an additional $100,000 for main floor flooding. These costs include structural damage costs and content costs. Benefits were not quantified for individual projects. However, a comparison of the existing and improved simulation results (Figure 7-8 vs. Figure 8-13) will provide a general understanding of the anticipated benefits of all improvements combined. Cost Estimates The estimated costs for all the evaluated improvement concepts are summarized in Table 8-1 below. Detailed costs estimates are provided in Appendix E. The total costs of implementing the recommended options is $98.5 million. It should be noted that these costs include a 50% contingency (typical for concept design) and a 15% engineering. Table 8-1: Conceptual Costs Summary Location Northridge Area (North-Central) Avondale / Montrose Area (North-Central) Highland Park / Swanavon Area (Central) Ivy Lake / Cobblestone / Smith Area (Central-East) Richmond Industrial Area (Central-West) TOTAL

Estimated Costs (incl. 50% contingency and 15% engineering) $

24.7 M

23.2 M

14.3 M

11.0 M

25.3 M

98.5 M

Recommendations The above drainage improvement recommendations are aimed at providing a 100-year level of flood protection for the most at-risk areas of the City, which is the targeted level of flood protection for the City and most other Alberta municipalities. Through the development and

Sameng Inc.

8.10

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

assessment of improvement concepts, it was concluded that a significant amount of drainage improvements will be necessary to achieve that level of service. Many of these improvements are very costly and may be challenging to be implemented in an urban setting (e.g. conflict with other utilities, construction impacts). For some areas, the cost-benefit of achieving a 100-year level of flood protection may be so poor, that it may not be financially possible to increase it. Furthermore, implementing nearly $100M of drainage upgrades would not be achievable in the short-term and would likely have to be spread over decades. However, it may be possible to implement some drainage upgrades to at-least enhance the level of flood protection for these areas. It is recommended that additional conceptual studies be completed to further investigate the drainage issues in these at-risk areas. The main goal of these studies would be to: 1) identify the flood risks of these areas under various design rainfall events to better understand their vulnerability to flooding (e.g. 10-year, 25-year, 50-year â&#x20AC;&#x201C; this master plan only reviewed flood risks for the 5 and 100-year events); 2) refine the proposed improvements and/or develop additional cost-effective improvements for these areas, and update the cost estimates; 3) confirm all possible conflicts with other utilities (e.g. other storm sewers, sanitary sewers, watermains, gas lines, power, communications, fibreoptic, etc.) 4) identify drainage improvements that could be implemented to enhance the level of flood protection but at a much lower cost (e.g. provide a 25-year level of flood protection at 10% of the cost of providing a 100-year level of flood protection). Ideally, these improvements could be staged to ultimately achieve a 100-year level of flood protection for the area. 5) Develop an implementation plan / prioritization plan that attempts to increase the level of flood protection for all at-risk areas of the City at once. For example, provide a 25year level of flood protection for all 11 at-risk areas within the next decade, instead of providing a 100-year of flood protection to only 3 of them within that same timeframe. Under this scenario, a larger part of the City would be resilient to flooding. The City should inform home-owners and business owners about the flood risks in their areas and how they could protect their own properties against flooding. This may include proper lot grading around their house/building, not parking on flood-prone streets during intense rainfalls. Furthermore, the City should continue to mandate on-site stormwater control for areas with poor major drainage system; this will eventually reduce street flooding. The City should look at upsizing storm sewer pipes in these at-risk areas when it becomes time to replace them (e.g. due to age, structural deficiencies). This may prevent having to install a second large sewer pipe to reduce flood risks.

Sameng Inc.

8.11

INT

100 ST

LEGEND PROPERTY LINE

INT

PROPOSED STORM PIPE

INT

PROPOSED DITCH

INT

PROPOSED MANHOLE PROPOSED STORMWATER MANAGEMENT FACILITY INT INT

PROPOSED MAJOR DRAINAGE / ROAD REGRADING

INT INT

INT

PROPOSED BERM INT

PROPOSED OVERFLOW

INT INT

INT

INT INT

INT INT INT

INT

X L/S

INT

IN/OUTLET

DRAINAGE IMPROVEMENTS CONCEPT FOR NORTHRIDGE AREA

PROPOSED CATCHBASIN INLET/GRATE WITH PROPOSED CAPTURE RATE

INT IN/OUTLET

IN/OUTLET INT INT

INT INT

INT

116 AVE

INT

750 CSP 1969 12.20 0.64

INT

300 CONC 1969 10.96 2.00

300 CONC 1969 16.53 9.86

300 CONC 1969 7.23 3.87

INT

DRAINAGE IMPROVEMENTS CONCEPT FOR AVONDALE / MONTROSE AREA

108 AVE

SECTION 20.00

AUGERED

12.19

10.97

DRAINAGE IMPROVEMENTS CONCEPT FOR IVY LAKE / COBLESTONE / SMITH AREA

IN/OUTLET

INT

15.00 AUGERED

INT INT

INT

DRAINAGE IMPROVEMENTS CONCEPT FOR RICHMOND AREA

100 AVE

INT

100 AVE (HWY 43)

INT

300 CMP 1996 22.70 3.00

300 CSP 1996 17.00 2.00

39.98 AUGERED SECTION

23.99 AUGERED SECTION

22.98 AUGERED SECTION

97 AVE

500 CMP 1980 16.50 0.00

Prepared By:

INT

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

INT

Client:

LINE RAIL INT

Project:

DRAINAGE IMPROVEMENTS CONCEPT FOR THE HIGHLAND PARK / SWANAVON AREA

Storm Drainage Master Plan 2018

84 AVE AUGERED SECTION

O RES

100 ST

108 ST

116 ST INT

OAD

ES R

INT

URC

INT

Title:

92 ST

84 AVE

Overview of Drainage Imporovement Concepts for Developed Areas

Scale:

Figure:

1:20,000

8-1

101 ST

102 ST

103B ST

LEGEND PROPERTY LINE PROPOSED STORM PIPE PROPOSED DITCH PROPOSED MANHOLE PROPOSED STORMWATER MANAGEMENT FACILITY

128 AVE 105 ST

PROPOSED MAJOR DRAINAGE / ROAD REGRADING

IMPROVE / LOWER OVERFLOW POINT 1,300 L/s 2,800 L/s 1500 Ø 1200 Ø

PROPOSED BERM PROPOSED OVERFLOW

124 AVE

X L/S

PROPOSED CATCHBASIN INLET/GRATE WITH PROPOSED CAPTURE RATE

1500 Ø

ALTERNATIVE OPTION TO PIPE ON 102 STREET IMPROVE DITCH TO FACILITATE OVERFLOW TOWARDS SOUTH (DEEPEN AND WIDEN) (MAY NOT BE NEEDED IF PIPE AND CATCHBASINS INSTALLED AS SHOWN) IMPROVE / LOWER / WIDEN DITCH

INSTALL 1500 Ø OUTLET TO LOWERED DITCH AND INTERCONNECT TO EX 1800 Ø PIPE (TO RELIEVE EXISTING SEWER AND INCREASE CAPACITY) INTERCONNECT TO EX 1200 Ø PIPE AT MANHOLE

2100 Ø

ROYAL OAKS DRIVE

1500 Ø

2100 Ø

INTERCONNECT TO EX 900 Ø PIPE WITH 1200 Ø PIPE

UPGRADE CULVERT TO 1600 Ø AND LOWER ROAD TO FACILITATE OVERFLOW TO SOUTH

3,200 L/s

REDUCE/REMOVE EXISTING CULVERT EAST OF RAILROAD

INTERCONNECT 2100 Ø PIPE TO EX 2100 Ø PIPE (TO RELIEVE EXISTING SEWER AND INCREASE CAPACITY)

20,000 L/s

0Ø

2100 Ø 0Ø

116 AVE

L/s 0,000

2100 Ø

DEEPEN DITCH BY ±0.5m (WIDEN AS NEEDED)

REPLACE EX 1500 Ø PIPE WITH 2100 Ø PIPE

210

INTERCONNECT 2100 Ø PIPE TO EX 2100 Ø PIPE (TO RELIEVE EXISTING SEWER AND INCREASE CAPACITY)

INSTALL PIPE INLET IN DITCH NORTH OF ROAD (DESIGNED TO CAPTURE 7200 L/s)

180

1500 Ø

100 L/s

1800 Ø 1800 Ø

0Ø

120

Prepared By:

DEEPEN DITCH BY ±1.0m (WIDEN AS NEEDED)

INSTALL 900 Ø PIPE (ALLOWS LOW FLOWS IN PIPE TO GO TO OUTFALL #1)

EX OUTFALL #1

REGRADE TO ENSURE ROAD OVERFLOWS INTO DITCH (PREVENT IT FROM GOING SOUTH INTO RESIDENTIAL AREA)

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

BERM TO PREVENT SURFACE OVERFLOW FROM GOING SOUTH (FORCE OVERFLOW TO WEST)

REPLACE EXISTING CULVERT TO 2100 Ø

Client:

INSTALL 2700 Ø OVERFLOW OUTFALL Project:

Storm Drainage Master Plan 2018 Title:

98 ST

100 ST

101 ST

102 ST

110 AVE

104 ST

106 ST

111 AVE DEWIT DR

2700 Ø

DEEPEN DITCH BY ±1.5m (WIDEN AS NEEDED)

INSTALL LARGE OVERFLOW INLET

2700 Ø

REPLACE EX CULVERT WITH 1500 Ø AT LOWER ELEVATION

Drainage Improvement Concepts for Northridge Area

Scale:

Figure:

1:7000

8-2

LEGEND PROPERTY LINE

114 AVE

PROPOSED STORM PIPE PROPOSED DITCH PROPOSED MANHOLE PROPOSED STORMWATER MANAGEMENT FACILITY

REGRADE ROAD TO FORCE SURFACE FLOWS WEST, NOT SOUTH.

PROPOSED MAJOR DRAINAGE / ROAD REGRADING PROPOSED BERM

EXISTING SURGE POND

PROPOSED OVERFLOW X L/S

REGRADE ROAD TO PREVENT SURFACE FLOWS FROM FLOWING WEST ON 113 AVENUE

600 L/S REGRADE/IMPROVE CAPACITY OF MAJOR DRAINAGE OVERFLOW PATH

PURPOSE OF THESE SEWERS IS TO PREVENT EXISTING DRY POND FROM OVERFLOWING RAILROAD AND POSING SIGNIFICANT FLOOD RISK TO RESIDENTS

PURPOSE OF REGRADING WORK IS TO REDUCE FLOOD RISK DUE TO LARGE PONDING DEPTHS IN THIS AREA

400 L/S

1050 Ø

111 AVE

PROPOSED CATCHBASIN INLET/GRATE WITH PROPOSED CAPTURE RATE

1050 Ø

ALTERNATIVE OVERFLOW RELIEF ALIGNMENT AS AN ALTERNATIVE TO THE 1050 Ø / 1500 Ø PIPE, INSTALL A POND OVERFLOW PIPE ACROSS RAILROAD TO 99 STREET AND LET WATER OVERFLOW ROAD

INTERCONNECTION TO EX 750 Ø PIPE WITH 1050 Ø PIPE

INTERCONNECTION TO EXISTING 525 Ø PIPE WITH 900 Ø PIPE

1500 L/S

2300 L/S 700 L/S

2100 Ø

1050 Ø

1500 Ø 1500 Ø

1800 Ø

1500 Ø

ION

20.00

RED AUGE

SECT

INTERCONNECT TO EXISTING 450 Ø WITH 525 Ø

107 AVE 2100 Ø

INTERCONNECT TO EXISTING 600 Ø WITH 900 Ø PIPE

2100 Ø

106 AVE

10.97

600 CONC 1959 128.70 1.00

12.19

105 AVE

THE PURPOSE OF THESE SEWER PIPES IS PURELY FOR CONVEYANCE OF THE UPSTREAM UPGRADES 600 1959 43.30 1.00

600 1959 59.20 0.50

PURPOSE OF THESE PIPE AND LARGE CAPACITY CB GRATES IS TO REDUCE SURCHARGE AND INCREASE FLOW CAPACITY IN EXISTING SEWERS, PREVENT MAJOR DRAINAGE FLOWS FROM FLOWING SOUTH INTO VULNERABLE AREAS, AND FOR CONVEYANCE OF UPSTREAM UPGRADES

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

600 1959 108.20 0.50

525 1959 12.19 0.50

600 CONC 1959 22.00 1.00

UPGRADE EXISTING 525 Ø TO 900 Ø PIPE (TO RELIEVE EXISTING SEWER ON 105 STREET TO FLOW WEST INTO THE 1050 Ø PIPE)

Project:

104 AVE

UPGRADE EXISTING 1050 Ø OUTFALL TO 2400 Ø OUTFALL

375 STL 70.30 (ABDN)

Storm Drainage Master Plan 2018 Title:

Drainage Improvement Concepts for Avondale / Montrose Area 98 ST

100 ST

250 CONC 1977 65.50 9.98

101 ST

103 AVE 102 ST

REGRADE SUCH THAT MAJOR DRAINAGE OVERFLOW FROM THE STREET GOES INTO RESERVOIR, NOT EAST INTO STREET DEPRESSION

INTERCONNECT TO EXISTING 600 Ø PIPE WITH 900 Ø PIPE

2500 L/S

2100 Ø

108 AVE

2100 Ø

INTERCONNECT TO EXISTING 450 Ø PIPE WITH 750 Ø PIPE

INTERCONNECT TO EXISTING 600 Ø PIPE WITH 900 Ø PIPE

1500 Ø

AS AN ALTERNATIVE OPTION TO REGRADING, THE EX PIPE COULD BE UPSIZED TO 900 Ø

1050 Ø

110 AVE

Scale:

Figure:

1:5000

8-3

100 AVENUE

LEGEND PROPERTY LINE PROPOSED STORM PIPE PROPOSED DITCH

99 AVENUE

PROPOSED MANHOLE PROPOSED STORMWATER MANAGEMENT FACILITY PROPOSED MAJOR DRAINAGE / ROAD REGRADING PROPOSED BERM PROPOSED OVERFLOW

RAIL LINE X L/S

INTERCONNECTION TO 375 Ø WITH 600 Ø

PROPOSED CATCHBASIN INLET/GRATE WITH PROPOSED CAPTURE RATE

97 AVENUE

INSTALL 1800 Ø OUTFALL INTO BEAR CREEK

1800 Ø

96 AVENUE 1500 Ø

95 AVENUE

1800 Ø

93 AVENUE

INTERCONNECTION TO EXISTING 375 Ø WITH 600 Ø PIPE

1800 Ø

1200 Ø

INTERCONNECTION TO EXISTING 375 Ø WITH 600 Ø PIPE

PURPOSE OF THESE UPGRADES IS TO CAPTURE ALL SURFACE RUNOFF TO PREVENT FLOODING AT LARGE DEPRESSION ON 99 STREET AND TO REDUCE SURCHARGE IN EXISTING SEWERS

91 AVENUE

1800 Ø

PURPOSE OF THESE PIPES IS TO CONVEY FLOW FROM UPSTREAM UPGRADES, AND RELIEVE SURCHARGE IN EXISTING SEWERS, THUS INCREASING THEIR FLOW CAPACITY AND REDUCE STREET PONDING THROUGHOUT

99 STREET

INT

OPTIONAL RECONNECT EXISTING 750mm Ø PIPE TO NEW PIPE AND ABANDON EXISTING OUTFALL (MAY NEED TO INCREASE NEW OUTFALL SIZE)

INTERCONNECTION TO 525 Ø WITH 900 Ø

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

90 AVENUE

98 STREET

100 STREET

Title:

ROA

101 STREET

Storm Drainage Master Plan 2018

CES

STR

Project:

OUR

EET

RES

88 AVENUE

INT

102

0Ø 180

PURPOSE OF THESE UPGRADES IS TO CAPTURE ALL SURFACE RUNOFF TO PREVENT FLOODING AT LARGE DEPRESSION ON 96 AVENUE AND REDUCE SURCHARGE IN EXISTING SEWERS

1500 Ø

OPTIONAL RECONNECT EXISTING 300mm Ø PIPE TO NEW PIPE AND ABANDON EXISTING OUTFALL

INTERCONNECTION TO EXISTING 375 Ø WITH 600 Ø PIPE

Drainage Improvements Concept for Highland Park / Swanavon

Scale:

Figure:

1:5000

8-4

LEGEND PROPERTY LINE PROPOSED STORM PIPE

INTERCONNECT TO EXISTING 1050 Ø PIPE WITH 1200 Ø PIPE.

PROPOSED DITCH

200 PVC 1995 37.10 0.50 200 PVC 1995 14.00 0.50

INSTALL LARGE GRATE TO CAPTURE STREET DRAINAGE

REGRADE LOCAL ROAD TO PREVENT MAJOR DRAINAGE ON 100 AVENUE FROM FLOWING SOUTH INTO LOCAL NEIGHBOURHOOD

250

PROPOSED STORMWATER MANAGEMENT FACILITY

PROPOSED MAJOR DRAINAGE / ROAD REGRADING PROPOSED BERM

21 00

200

PROPOSED MANHOLE

200 PVC 1995 13.10 0.50

2100 Ø

100 AVENUE

PROPOSED OVERFLOW

100 AVENUE X L/S

REGRADE INTERSECTION AND PATHWAY TO PREVENT OVERFLOW FROM INTERSECTION FROM FLOWING INTO RESIDENTIAL AREAS. (SHORT BERM IF NEEDED) TRY TO FORCE OVERFLOW TO THE EAST IF POSSIBLE.

PROPOSED CATCHBASIN INLET/GRATE WITH PROPOSED CAPTURE RATE

PURPOSE IS TO REDUCE PONDING DEPTH AT INTERSECTION AND PREVENT OVERFLOW INTO RESIDENTIAL AREA

REGRADE TO HAVE MAJOR DRAINAGE FLOW SOUTH (NOT EAST INTO THE RESIDENTIAL DEVELOPMENT) PURPOSE OF REGRADING WORK IS TO PREVENT SURFACE DRAINAGE FROM FLOWING INTO RESIDENTIAL AREA, WHICH HAS POOR MAJOR CONVEYANCE FORCES WATER TO STAY ON MAIN ROADS WHICH ARE WELL GRADED.

93 D 19 NE DO AN AB

BRK

500 CMP 1980 16.50 0.00 BRK

BRK

REGRADE LOCAL ROADS TO PREVENT MAJOR DRAINAGE FROM 92 STREET FROM FLOWING INTO LOCAL RESIDENTIAL AREAS

92 STREET

CURRENT MAJOR DRAINAGE PATH (HAS CAPACITY CONSTRAINTS) UPGRADE MAJOR DRAINAGE OVERFLOW AS NEEDED

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

BRK

CULVERT

92 AVENUE

300 PV 5

0 0.3

9 8.7

C 200

Project:

PV 375

Storm Drainage Master Plan 2018

0 .00 0.3 09 94 C 20

CULVERT 450

0.20

450

C 600 PV

56.69 2009

0 .20 0.2 09 67 C 20

PVC

IMPROVE DITCH DRAINAGE (AND CULVERT TO CONVEY MAJOR DRAINAGE OVERFLOW MORE EFFICIENTLY FROM NORTH INTO WOODY CHANNEL)

Title:

Drainage Improvement Concept for Ivy Lake / Coblestone / Smith Area

Scale:

Figure:

0.2 93.46 2009

9 XX

C 200

300 PV

1:2500

8-5

XX 0.1

IN/OUTLET

INT

LEGEND INT

PROPERTY LINE

INT

BRK

(ABD N)

INT

PROPOSED STORM PIPE

INT

(ABDN)

INT

(ABDN)

PROPOSED DITCH BRK

BRK

PROPOSED STORMWATER MANAGEMENT FACILITY

BRK

PROPOSED LARGE CATCHBASIN GRATE PROPOSED MAJOR DRAINAGE / ROAD REGRADING BRK

PROPOSED BERM INT

INT

PROPOSED OVERFLOW

100 AVE (HWY 43) IMPROVE RAILROAD DITCH

IMPROVE OVERFLOW INTO RAILROAD DITCH ENSURE FLOW CONTROL ORIFICE EXISTS

REMOVE / DOWNSIZE CULVERTS AT ROAD

97 AVE

600mm Ø CONNECTIONS TO UPGRADED PIPE OVERFLOW TO POND

INTERCONNECT TO EXISTING 1200mm Ø

UPGRADE EXISTING PIPE TO 1500 Ø FROM DEPRESSION TO POND

1200 Ø 1500 Ø

IMPROVE OVERFLOW TO RAILROAD DITCH

LINE RAIL

CONSTRUCT DRY POND AND CONNECT TO EX SYSTEM ON BOTH SIDES OF POND (17,000m³)

BERM TO PREVENT DITCH FLOW FROM FLOODING PROPERTIES

MAINTAIN EXISTING ORIFICE

EXPAND POND TO PREVENT OVERFLOW DURING 100 YEAR EVENT

EEK R CR

IMPROVE RAILROAD DITCH ON BOTH SIDES, FLOWING EAST

BEA

ENSURE SURFACE FLOW FROM THIS DEVELOPMENT IS TOWARDS POND

INSTALL LARGE GRATE TO CAPTURE SURFACE RUNOFF AND PREVENT IT FROM FLOWING EAST (RAISE ROAD AS NEEDED AND PROVIDE OVERFLOW TO POND)

MAINTAIN EX CULVERTS AND ENSURE FLOWS STAY ALONG RAILROAD

INT

MAINTAIN EXISTING ORIFICE

RAISE ROAD TO REDUCE PONDING DEPTH

REVIEW POSSIBILITY OF COMBINING THE MANY CULVERTS AS ONE LONG PIPE (LESS HEAD LOSS)

LOWER INTERSECTION TO FACILITATE OVERFLOW TO EAST OF ROAD AND INTO CANFOR DITCH

MAINTAIN EXISTING CHANNEL DEPTH

89 AVE UPSIZE TO 2100 Ø (CONNECT TO GRATE

UPGRADE CULVERTS TO 3m SPAN + 2.4m RISE BOX CULVERTS WITH CONCRETE HEAD WALL

111A STREET

MAINTAIN EXISTING ORIFICE

Prepared By:

UPGRADE 1050 Ø TO 2400 Ø PIPE AND MAINTAIN EX 1800 Ø PIPE

UPGRADE OUTFALL TO 2400 Ø AND / OR LOWER OVERFLOW ELEVATION #1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

PROPOSED RICHMOND POND

1200 Ø

UPSIZE TO 1500 Ø

UPGRADE 1500 Ø TO 2100 Ø PIPE AND MAINTAIN EX 1650 Ø PIPE

Client:

84 AVE CONNECT TO EX 1200 Ø

Storm Drainage Master Plan 2018

108 ST

116 ST

110 ST

Project:

Title:

INT BRK

INT

Drainage Improvement Concept for Richmond Industrial Area (Option 1)

INT

Scale:

Figure:

INT

1:10,000

8-6

IN/OUTLET

INT

LEGEND INT

PROPERTY LINE

INT

BRK

(ABD N)

INT

PROPOSED STORM PIPE

INT

(ABDN)

INT

(ABDN)

PROPOSED DITCH BRK

BRK

PROPOSED STORMWATER MANAGEMENT FACILITY

BRK

PROPOSED LARGE CATCHBASIN GRATE PROPOSED MAJOR DRAINAGE / ROAD REGRADING BRK

PROPOSED BERM INT

INT

PROPOSED OVERFLOW

100 AVE (HWY 43) IMPROVE RAILROAD DITCH

IMPROVE OVERFLOW INTO RAILROAD DITCH ENSURE FLOW CONTROL ORIFICE EXISTS

REMOVE / DOWNSIZE CULVERTSAT ROAD

97 AVE

600mm Ø CONNECTIONS TO UPGRADED PIPE

2100 Ø

EEK R CR

INSTALL LARGE GRATE TO CAPTURE SURFACE RUNOFF AND PREVENT IT FROM FLOWING EAST (RAISE ROAD AS NEEDED AND PROVIDE OVERFLOW TO POND)

MAINTAIN EX CULVERTS AND ENSURE FLOWS STAY ALONG RAILROAD

INT

2100 Ø

MAINTAIN EXISTING ORIFICE

LINE RAIL

UPGRADE EXISTING PIPE TO 1500 Ø

BEA

BERM TO PREVENT DITCH FLOW FROM FLOODING PROPERTIES

IMPROVE OVERFLOW TO RAILROAD DITCH

EXPAND POND TO PREVENT OVERFLOW DURING 100 YEAR EVENT

Ø 1200

2100 Ø

IMPROVE RAILROAD DITCH ON BOTH SIDES, FLOWING EAST

ENSURE SURFACE FLOW FROM THIS DEVELOPMENT IS TOWARDS POND

MAINTAIN EXISTING ORIFICE

REVIEW POSSIBILITY OF COMBINING THE MANY CULVERTS AS ONE LONG PIPE (LESS HEAD LOSS)

LOWER INTERSECTION TO FACILITATE OVERFLOW TO EAST OF ROAD AND INTO CANFOR DITCH

MAINTAIN EXISTING CHANNEL DEPTH

2400 Ø

89 AVE

UPGRADE CULVERTS TO 4.8m SPAN + 2.4m RISE BOX CULVERTS WITH CONCRETE HEAD WALL

UPSIZE TO 2100 Ø (CONNECT TO GRATE

MAINTAIN EXISTING ORIFICE

RAISE ROAD TO REDUCE PONDING DEPTH

Prepared By:

UPGRADE 1050 Ø TO 2400 Ø PIPE AND MAINTAIN EXISTING 1800 Ø PIPE UPGRADE 1500 Ø TO 2100 Ø PIPE AND MAINTAIN EX 1650 Ø PIPE

UPSIZE TO 1500 Ø

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

1200 Ø

PROPOSED RICHMOND POND

UPGRADE OUTFALL TO 2400 Ø AND / OR LOWER OVERFLOW ELEVATION

Client:

84 AVE CONNECT TO EX 1200 Ø

Storm Drainage Master Plan 2018

108 ST

116 ST

110 ST

Project:

Title:

INT BRK

INT

Drainage Improvement Concept for Richmond Industrial Area (Option 2)

INT

Scale:

Figure:

INT

1:10,000

8-7

IN/OUTLET

INT

LEGEND INT

PROPERTY LINE

INT

BRK

(ABD N)

INT

PROPOSED STORM PIPE

INT

(ABDN)

INT

(ABDN)

PROPOSED DITCH BRK

BRK

PROPOSED STORMWATER MANAGEMENT FACILITY

BRK

PROPOSED LARGE CATCHBASIN GRATE PROPOSED MAJOR DRAINAGE / ROAD REGRADING BRK

PROPOSED BERM INT

INT

PROPOSED OVERFLOW

100 AVE (HWY 43) IMPROVE RAILROAD DITCH

IMPROVE OVERFLOW INTO RAILROAD DITCH ENSURE FLOW CONTROL ORIFICE EXISTS

REMOVE / DOWNSIZE CULVERTS AT ROAD

97 AVE

OVERFLOW TO POND

MAINTAIN EXISTING ORIFICE

INT

LINE RAIL

EEK R CR

1200 Ø 1500 Ø

IMPROVE OVERFLOW TO RAILROAD DITCH

EXPAND POND TO PREVENT OVERFLOW DURING 100 YEAR EVENT

UPGRADE EXISTING PIPE TO 1500 Ø FROM DEPRESSION TO POND

BEA

ENSURE SURFACE FLOW FROM THIS DEVELOPMENT IS TOWARDS POND

CONSTRUCT DRY POND AND CONNECT TO EX SYSTEM ON BOTH SIDES OF POND (17,000m³)

RAISE ROAD TO REDUCE PONDING DEPTH

REVIEW POSSIBILITY OF COMBINING THE MANY CULVERTS AS ONE LONG PIPE (LESS HEAD LOSS)

LOWER INTERSECTION TO FACILITATE OVERFLOW TO EAST OF ROAD AND INTO CONFOR DITCH

MAINTAIN EXISTING CHANNEL DEPTH

RICHMOND POND EXPANSION (OR 2100 Ø INSULATED PIPE)

MAINTAIN EX CULVERTS AND ENSURE FLOWS STAY ALONG RAILROAD

OVERFLOW GRATE @ 658.41 (UPSTREAM OF ORIFICE) WEIRD @ 657.90

89 AVE

MAINTAIN EXISTING ORIFICE

UPGRADE CULVERTS TO 3m SPAN + 2.4m RISE BOX CULVERTS WITH CONCRETE HEAD WALL

MAINTAIN EXISTING ORIFICE

INSTALL LARGE GRATE TO CAPTURE SURFACE RUNOFF AND PREVENT IT FROM FLOWING EAST (RAISE ROAD AS NEEDED AND PROVIDE OVERFLOW TO POND)

Prepared By:

UPGRADE 1050 Ø TO 2400 Ø PIPE AND MAINTAIN EX 1800 Ø PIPE

UPSIZE TO 2100 Ø (CONNECT TO GRATE

UPGRADE 1500 Ø TO 2100 Ø PIPE AND MAINTAIN EX 1650 Ø PIPE

UPSIZE TO 1500 Ø

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

1200 Ø

PROPOSED RICHMOND POND

UPGRADE OUTFALL TO 2400 Ø AND / OR LOWER OVERFLOW ELEVATION

Client:

84 AVE CONNECT TO EX 1200 Ø

Storm Drainage Master Plan 2018

108 ST

116 ST

110 ST

Project:

Title:

INT BRK

INT

Drainage Improvement Concept for Richmond Industrial Area (Option 3)

INT

Scale:

Figure:

INT

1:10,000

8-8

IN/OUTLET

INT

LEGEND INT

PROPERTY LINE

INT

BRK

(ABD N)

INT

PROPOSED STORM PIPE

INT

(ABDN)

INT

(ABDN)

PROPOSED DITCH BRK

BRK

PROPOSED MANHOLE

BRK

PROPOSED STORMWATER MANAGEMENT FACILITY PROPOSED LARGE CATCHBASIN GRATE BRK

PROPOSED MAJOR DRAINAGE / ROAD REGRADING INT

INT

PROPOSED BERM

100 AVE (HWY 43)

PROPOSED OVERFLOW

IMPROVE RAILROAD DITCH

IMPROVE OVERFLOW INTO RAILROAD DITCH REMOVE / DOWNSIZE CULVERTS AT ROAD

97 AVE

IMPROVE OVERFLOW TO RAILROAD DITCH

1200 Ø 1500 Ø

EEK R CR

PREVENT DITCH FLOW FROM FLOWING EAST ALONG TRACKS (MONITOR OVERFLOW)

BEA

ENSURE SURFACE FLOW FROM THIS DEVELOPMENT IS TOWARDS POND

1200 Ø

ENSURE FLOW CONTROL ORIFICE EXISTS

CONSTRUCT DRY POND AND CONNECT TO EX SYSTEM ON BOTH SIDES OF POND (17,000m³)

2100 Ø TIE-IN TO EXISTING

MAINTAIN EXISTING ORIFICE

1500 Ø

300 Ø INT

RAISE ROAD TO REDUCE PONDING DEPTH (NOT MODELED)

REVIEW POSSIBILITY OF COMBINING THE MANY CULVERTS AS ONE LONG PIPE (LESS HEAD LOSS)

LOWER INTERSECTION TO FACILITATE OVERFLOW TO EAST OF ROAD AND INTO COMFOR DITCH (REDUCE MAX PONDING DEPTH) (NOT MODELED)

MAINTAIN EXISTING CHANNEL DEPTH

OVERFLOW GRATE EXPAND POND TO PREVENT OVERFLOW DURING 100 YEAR EVENT

WEIR @ 657.80m

LINE RAIL

MOVE PROPOSED ORIFICE TO HERE

INSTALL LARGE GRATE TO CAPTURE SURFACE RUNOFF AND PREVENT IT FROM FLOWING EAST (RAISE ROAD AS NEEDED AND PROVIDE OVERFLOW TO POND)

89 AVE

MAINTAIN EXISTING ORIFICE

2100 Ø

2400 Ø UPGRADE CULVERTS TO 3m SPAN + 2.4m RISE BOX CULVERTS WITH CONCRETE HEAD WALL

IN / OUT FLOW CB GRATE @ 658.0m UPSIZE TO 2100 Ø (CONNECT TO GRATE

Prepared By:

UPGRADE 1050 Ø TO 2400 Ø PIPE UPGRADE 1500 Ø TO 2100 Ø PIPE AND MAINTAIN EX 1650 Ø PIPE

UPSIZE TO 1500 Ø

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

1200 Ø

PROPOSED RICHMOND POND

UPGRADE OUTFALL TO 2400 Ø AND / OR LOWER OVERFLOW ELEVATION

Client:

84 AVE CONNECT TO EX 1200 Ø

Storm Drainage Master Plan 2018

108 ST

116 ST

110 ST

Project:

Title:

INT BRK

INT

Drainage Improvement Concept for Richmond Industrial Area (Option 4)

INT

Scale:

Figure:

INT

1:10,000

8-9

IN/OUTLET

INT

LEGEND INT

PROPERTY LINE

INT

BRK

(ABD N)

INT

PROPOSED STORM PIPE

INT

(ABDN)

INT

(ABDN)

PROPOSED DITCH BRK

BRK

PROPOSED STORMWATER MANAGEMENT FACILITY

BRK

PROPOSED LARGE CATCHBASIN GRATE PROPOSED MAJOR DRAINAGE / ROAD REGRADING BRK

PROPOSED BERM INT

INT

PROPOSED OVERFLOW

100 AVE (HWY 43) IMPROVE RAILROAD DITCH

IMPROVE OVERFLOW INTO RAILROAD DITCH ENSURE FLOW CONTROL ORIFICE EXISTS

REMOVE / DOWNSIZE CULVERTSAT ROAD

1200 Ø

97 AVE

TIE-IN TO EXISTING

MAINTAIN EXISTING ORIFICE

1500 Ø

300 Ø

1500 Ø

2100 Ø

OVERFLOW GRATE WEIR @ 657.80m

LINE RAIL

1500 Ø

INT

MOVE EXISTING ORIFICE TO HERE

INSTALL LARGE GRATE TO CAPTURE SURFACE RUNOFF AND PREVENT IT FROM FLOWING EAST (RAISE ROAD AS NEEDED AND PROVIDE OVERFLOW TO POND)

RAISE ROAD TO REDUCE PONDING DEPTH (NOT MODELED)

REVIEW POSSIBILITY OF COMBINING THE MANY CULVERTS AS ONE LONG PIPE (LESS HEAD LOSS)

LOWER INTERSECTION TO FACILITATE OVERFLOW TO EAST OF ROAD AND INTO CAMFOR DITCH (REDUCE MAX PONDING DEPTH) (NOT MODELED)

MAINTAIN EXISTING CHANNEL DEPTH

2400 Ø

89 AVE

MAINTAIN EXISTING ORIFICE

EEK R CR

PREVENT DITCH FLOW FROM FLOWING EAST ALONG TRACKS (MONITOR OVERFLOW)

IMPROVE OVERFLOW TO RAILROAD DITCH

EXPAND POND TO PREVENT OVERFLOW DURING 100 YEAR EVENT

1200 Ø

1200

BEA

ENSURE SURFACE FLOW FROM THIS DEVELOPMENT IS TOWARDS POND

UPGRADE CULVERTS TO 4.8m SPAN + 2.4m RISE BOX CULVERTS WITH CONCRETE HEAD WALL

IN / OUT FLOW CB GRATE @ 658.0m UPSIZE TO 2100 Ø (CONNECT TO GRATE

Prepared By:

UPGRADE 1050 Ø TO 2400 Ø PIPE

UPGRADE 1500 Ø TO 2100 Ø PIPE AND MAINTAIN EX 1650 Ø PIPE

UPSIZE TO 1500 Ø

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

1200 Ø

PROPOSED RICHMOND POND

UPGRADE OUTFALL TO 2400 Ø AND / OR LOWER OVERFLOW ELEVATION

Client:

84 AVE CONNECT TO EX 1200 Ø

Storm Drainage Master Plan 2018

108 ST

116 ST

110 ST

Project:

Title:

INT BRK

INT

Drainage Improvement Concept for Richmond Industrial Area (Option 5)

INT

Scale:

Figure:

INT

1:10,000

8-10

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

SURCHARGE DEPTH â&#x2030;¥ 1.0m BELOW GROUND 0.5 TO 1.0m BELOW GROUND 0.0 TO 0.5m BELOW GROUND

TWP RD 720

132 AVENUE

0.0 TO 0.5m ABOVE GROUND

100 STREET

> 0.5m ABOVE GROUND

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

OAD

R CES OUR RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN L

O'BR

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Proposed System 1:100-year 4-hour Event - Sewer Surcharge

Scale:

Figure:

1:40,000

8-11

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

THEORETICAL LOADING Qp / Qc â&#x2030;¤ 0.5 0.51 - 1.0

TWP RD 720

1.01 - 1.5

132 AVENUE

1.51 - 2.0

100 STREET

> 2.0

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

CES

OUR

RES

RGE RD 65

92 STREET

100 AVENUE

ROA

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

IEN O'BR

LAKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Proposed System 1:100-year 4-hour Event - Theoretical Loading in Pipe

Scale:

Figure:

1:40,000

8-12

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

SURFACE PONDING DEPTHS <0.15m 0.16m - 0.35m

TWP RD 720

0.36m - 0.50m

132 AVENUE

0.51m - 1.00m

100 STREET

>1.00m

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

AD S RO

E URC

O RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

O'BR

IEN L

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Proposed System 1:100-year 4-hour Event - Surface Ponding

Scale:

Figure:

1:40,000

8-13

LEGEND CITY BOUNDARY

148 AVENUE

PROPERTY LINE

PEAK SURFACE FLOW RATE 0 - 250 L/s 251 - 500 L/s

TWP RD 720

501 - 1000 L/s

132 AVENUE

1001 - 2000 L/s

100 STREET

> 2000 L/s

116 AVENUE

108 AVENUE

100 AVENUE

108 STREET

116 STREET

124 STREET

RGE RD 54

84 STREET

84 AVENUE Prepared By:

AD S RO

E URC

O RES

RGE RD 65

92 STREET

100 AVENUE

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

68 AVENUE

O'BR

IEN L

AKE

Project:

Storm Drainage Master Plan 2018 Title:

Simulation Results - Proposed System 1:100-year 4-hour Event - Peak Surface Flow Rate

Scale:

Figure:

1:40,000

8-14

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.0

City of Grande Prairie

Storm Drainage Master Plan for Future Development Areas Objectives of Storm Drainage Master Plan

One of the primary objectives of a Storm Drainage Master Plan is to provide a framework for planning and implementing drainage infrastructure to allow for growth and new developments. Infrastructure should be coordinated to provide consistent servicing throughout all new development. The Master Plan includes consideration for: • Standards for capturing runoff in the stormwater drainage system. • Conveyance of captured runoff to storage facilities and outfalls to prevent flooding. • Stormwater Management Facilities to buffer peak flows and manage water quality. • Plan for maintenance and operational requirements. • Monitor the system. Overview of Previous Storm Drainage Master Plan’s Drainage Concepts for Future Servicing Areas The previous Storm Drainage Master Plan, prepared in 2012, generally followed existing drainage patterns, placing a number of proposed stormwater management facilities within wetlands or other potentially environmentally significant areas. The plan identified 117 proposed storage facilities, including ponds proposed in current Area Structure Plans and Outline Plans. All ponds in the master plan were specified to limit outflows to 5 L/s/ha, and store at least 500 m³/hectare (4.9 million m³) of the gross developable land. Based on these given storage volumes and the traditional storm pond design criteria, the drainage plan would have storm ponds occupy at least 450 hectares of land, including some setback space. The 2012 plan report included a discussion of the environmental impacts of this approach. Figures 6-9 through 6-13 from the 2012 report show the overlap of proposed storm ponds and environmental areas. Approximately 588 hectares of environmentally sensitive areas are overlapped by storage facilities in the drainage plan. The 2012 drainage plan follows traditional stormwater management principals and it will work. The benefit of such a plan is that it follows tradition and the key stakeholders in the development of land have established processes to review and approve the subdivision proposals. The disadvantage of the plan is that it does not fully integrate the need for stormwater management with the preservation of natural water features of the land. In this regard, the utilization of land is not optimum, requiring the construction of man-made storage in addition to the preservation and sometimes compensation for the destruction of natural wetlands. The purpose of the current plan is to provide an alternative approach to stormwater management in the traditional sense. The goal is to achieve a more integrated approach to Sameng Inc.

9.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

stormwater management and the preservation of the environment. The plan objective is to ensure the level of flood protection of the stormwater management system while at the same time, maximize the preservation of natural water features within the proposed development area. Receiving System Capacities The topography of the future development areas of the City indicate that most new developments can drain to new outfalls rather than to connect with existing infrastructure. The major drainage basins are shown in Figure 4-4. The current standard release rate of 5 L/s/ha will apply to developments draining directly to Bear Creek, either through existing or new outfalls. This has been an established practice for many years and has proven to help with the stability of Bear Creek. It should therefore continue. For development that will discharge to waterbodies other than Bear Creek, the capacity of the receiving streams, lakes, and channel will need to be studied to determine an appropriate release rate from developing lands. These individual studies are out of the scope of the current master plan. The studies themselves may require the collaboration of the City and the County of Grande Prairie. Environmental Considerations 9.4.1

General

Urban development affects both aquatic and terrestrial ecosystems, and measures to mitigate these effects can vary; from the protection of a single species, to broad natural reservations. For the purposes of this master plan, environmental considerations discussed here are specific to protecting aquatic environmental assets and streamlining approval processes from government agencies. Considerations for the protection of aquatic environments are covered in existing legislation on the provincial and federal level. Environmental laws relevant to stormwater drainage in Grande Prairie include the Water Act (Alberta), the Environmental Protection and Enhancement Act (EPEA) (Alberta), the Fisheries Act (Canada), the Public Lands Act (Alberta) and the Migratory Birds Convention Act (Canada). In addition, there are policies, guidelines, codes of practice, and white papers relating to surface water that fit into the above legislations. Under current general practice, the onus has been on developers to fulfil these various legal requirements individually, for each stage of development. This master plan outlines how the process can be made more comprehensive, and more efficient. In recent years, updates to the wetland policy more strongly encourage avoiding and minimizing disruption to wetlands, over compensation. To reflect that, the drainage master plan should emphasize leaving wetlands in their natural state as much as possible, while

Sameng Inc.

9.2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

utilizing the storage and water quality treatment they naturally provide for the benefit of the overall drainage system. The following sub-sections outline how the various legislations apply to development, specifically in the City of Grande Prairie. 9.4.2

Environmental Protection and Enhancement Act (EPEA)

All components of a municipal stormwater drainage system require registration under the EPEA before they are constructed. This registration is to ensure that the design of the system conforms to current standards, guidelines, and best management practices, and that the infrastructure fits with the Drainage Master Plan for the City. As the current City of Grande Prairie standards agree with Provincial guidelines, there should be no issues with EPEA approvals, so long as City guidelines and the Master Drainage Plan are followed. 9.4.3

Water Act

The Water Act, with associated guidelines and regulations protects water resources in the Province from pollution, depletion, and flooding. Consideration in gaining approval for storm water infrastructure includes the following; • Minimize flooding and erosion • Minimize effect to aquatic environments • Maintain natural streams and wetlands • Restrict development below the 100-year flood level • Conform with approved master drainage plans • Minimize impact on groundwater, and erosion and sediment transport in receiving basins • Provide runoff control to protect downstream drainage paths, prevent flooding, and capture sediments from runoff. Municipalities that prepare Master Drainage Plans can determine the cumulative impact on receiving waterbodies. These plans can be submitted for approval under the Water Act. This is a voluntary requirement; however, if a municipality can demonstrate the individual components comply with the Master Drainage Plan, there would be no requirement to get individual Water Act approvals on a project by project basis. The Water Act also covers the policies for preserving and/or compensating for wetlands and riparian setbacks. Any disturbance or removal of wetlands requires approval which may include monetary compensation. This approval process is generally slow compared to other approvals, and current policies strongly discourage the removal of significant wetlands. By identifying potentially significant wetlands in the master drainage plan, approvals for plans that avoid natural wetlands or incorporate them into the stormwater drainage system can be gained well in advance of development needs. Sameng Inc.

9.3

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.4.4

City of Grande Prairie

Public Lands Act

The bed and shore of lakes, rivers, streams and other natural waterbodies are considered public lands, and special dispositions must be granted by the Province before altering them in any way. Dispositions are granted based on the following criteria; • Altering the bed and banks cannot be reasonably avoided. • There is clear value in allowing the disposition. • There will be no negative long-term impacts of the alteration. • Short-term negative impacts will be limited in scope and timeframe (ie, defined construction time) In many cases, especially for smaller streams and waterbodies, the limits of bed and shore are unclear. In addition, small watercourses over flat terrain have the tendency to meander and evolve over time, which limits how long dispositions may be valid. The Master Plan should reduce the number of new outfalls required to Bear Creek and other waterbodies, and forebays should be designed to minimize the disruption to public lands. 9.4.5

Federal Legislation

Where certain species of birds and fish are thought to exist, federal regulations require assessments to determine potential disruption to breeding and nesting habitats, and approvals for mitigating these impacts. Of special consideration, the Trumpeter Swan nests primarily in the Grande Prairie area and is a protected species. Stormwater Management Planning 9.5.1

General

Stormwater Management is a process with several levels, from pollution avoidance, to watershed management strategies. By considering multiple components of stormwater management together, the master plan can identify opportunities for a plan that is greater than the sum of its parts. 9.5.2

Approach

The overall philosophy of this Drainage Master Plan is to use the natural topography, including existing wetlands, as much as possible. This will reduce disruption of natural runoff, and save in overall costs for development, maintenance, and environmental value. Figure 9-1 illustrates how natural features may be integrated into the stormwater management plan, with or without upstream storage ponds. To reduce the number, size, and construction costs of stormwater management facilities, the Master Plan focus on the establishment of ‘Water Retention and Conveyance Corridors’ along natural or existing drainage routes, especially around environmentally sensitive areas.

Sameng Inc.

9.4

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Where natural wetlands, lakes, and creeks have sufficient capacity, the requirement to limit discharge to 5 L/s/ha is relaxed, and developers would be required only to control for water quality. Depending on the type of facility used, (constructed forebay, infiltration trench, source control, etc.), the footprint required for stormwater management facilities can be significantly decreased. Consolidating storage to natural runoff corridors will promote more efficient land use. Naturally low areas are more likely to be unsuitable for development, and improving connectivity between these areas can establish better overland drainage and reduce the risk of flooding overall. It also promotes more effective use of naturally high ground, which is less likely to flood, and avoids the inefficiencies of underground pipes that drain contrary to the overland runoff direction. In addition, incorporating existing wetlands into the stormwater management system will save the cost of compensating for wetland disruption, which is currently at a 3:1 ratio for most wetlands. Drainage corridors can be incorporated into transportation plans as well, as they may be designed to act as walking/biking trails during dry conditions. By establishing drainage corridors, development of flood-prone locations will be avoided, and trunk sizes and lengths can be reduced. 9.5.3

Stormwater Management Facility Types

There are many options for stormwater management that are applicable in the City of Grande Prairie. Selecting the most appropriate facility is based on the local needs for water quality, flood protection, flow regulation, and environmental considerations. Following is a brief description of the various SWMF types and their application. The applicability of these various facility types is summarized in Table 9-1. Table 9-1: Applicability of Stormwater Management Facility Types Facility Type Dry Pond Wet Pond Wetland Forebay Bioswale Drainage Parkway Filter Strip

Runoff Retention Yes Yes Yes Yes Limited Yes

Sameng Inc.

Conveyance

Yes Yes

9.5

Water Quality Yes Yes Yes Yes Yes Yes

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

• Wet Ponds – are conventional facilities that have become standard practice over the last 30 years. These facilities have a permanent water surface deep enough to prevent plant growth at the bottom of the pond. These ponds improve water quality by providing enough ‘dead storage’ to settle out impurities, and they have a ‘live storage’ and freeboard component for flood prevention and flow regulation. Enhanced wet ponds may incorporate wetland features or park amenities as well. For developments using wet ponds, typically 5% of the basin area is reserved for these facilities, including setbacks and landscaping features. • Dry Ponds – are normally dry and may accommodate sports fields, dog parks or other recreation amenities most of the time. They are not considered reliable for treatment of water quality, unless combined with structures specific for that purpose (see below). Dry ponds typically require more maintenance than wet ponds to clean out sediment before it can be taken up again in subsequent events. For dry ponds storing 100-year runoff events, typically 5% of the basin area is reserved for the pond, though the land may also be used for recreation at most times. Dry ponds are only recommended for this plan near the Grande Prairie Airport. • Wetlands – Constructed wetlands may be natural areas that are incorporated into a municipal drainage system, or they may be entirely man-made areas restored to a naturalized state. An example of the features common in constructed wetlands are shown in Figure 9-2. Constructed wetlands differ from wet ponds in that they maintain a permanently wet area that is shallow enough to promote vegetation throughout the wetland. Forebays and vegetated strips provide additional water quality improvements and reduce the risk of erosion and sedimentation. Wetlands are designed to promote a variety of vegetation and wildlife, which reduces the cost of maintenance for healthy wetlands. The water level in marsh zones should not vary more than 1 metre for events smaller than 1:25 years. For this reason, wetlands necessarily occupy a greater total area than conventional ponds, up to about 10% of the basin area they serve. • Forebays – are outlet structures at lakes, streams, and wetlands designed for water quality and erosion protection. They are used when the receiving waterbody is large enough to accept most of the volume of a developed watershed but must be protected from pollution or high inlet velocities. Forebays consist of small permanently wet ponds that buffer peak flows and dissipate energy from high discharge velocities. Forebays are generally subject to hazardous flows, and so should be fenced off from the public and wildlife. Forebays are compact facilities, typically about 10% to the area of the pond or wetland they are attached to, but they may be expanded to provide additional storage volume. • Filter Strips – These are vegetated setbacks that accept stormwater runoff as sheet flow and convey it to wetlands or catchbasins. These may be constructed with long grass or willow groves with fairly flat slopes. Filter strips may be used as a suitable transition between bioswales and wetlands/ponds, without the need for a dedicated forebay or inlet structure. The vegetation is typically naturalized, but it may be

Sameng Inc.

9.6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

cultivated to control nuisance species or for specific aesthetic. They are typically 10-20 meters wide. Filter strips are most appropriate where inflows are mild and/or infrequent, as consistent high flow volumes will cause the soil quality and vegetation to deteriorate over time. • Naturalized Drainage Parkways – combine elements of constructed wetlands, enhanced wet ponds, and other structures to create linear facilities that provide both conveyance and storage. An overview of the features often included in these facilities is shown in Figure 9-2. During frequent events, a stream or constructed channel conveys flows up to a defined rate, controlled by weirs or other structures. During intense events, the channel is allowed to flood to a certain level, providing storage and flood protection to surrounding lands. Vegetation and public facilities (walking trails, etc.) within the parkway are selected and designed to withstand occasional infrequent flooding without permanent damage. Naturalized Parkways typically require the same land reservation as wetlands, but they offer more flexibility in integrating recreational amenities. • Bioswale – These are grassed corridors that are already somewhat common in the newer developments of Grande Prairie. These facilities reduce runoff rates by capturing lot runoff and conveying it towards catchbasins or other facilities at a slower rate than pipes or channels. Bioswales can be attractive features in residential areas, but they require additional maintenance to clean and manage nuisance pests and mosquito breeding spots. Bioswales are often used in lieu of paved back alleys, or they are placed along pipeline ROWs. 9.5.4

Conveyance and Connectivity

Best practices for stormwater management systems includes both underground sewers and overland drainage. Underground sewers are typically sized to convey captured runoff up to a 1:5-year event, keeping water off roadways and providing adequate drainage to properties. Overland drainage systems are sized to convey 100-year peak flow rates, for flood prevention and conveying large runoff volumes safely to storage facilities and other areas designed for receiving these flows. When elevations allow for building stormwater management facilities in series, there are several advantages. It improves the effectiveness of treatment for water quality; it reduces the size of storm pipes, and it reduces the number of outfalls to lakes and creeks. Effective arrangement of facilities in series includes the design of conveyance between facilities, control structures, and overflows. Overland conveyance design includes the road network, to eliminate trapped low areas, and ensure positive drainage away from buildings. Overland drainage is important in providing alternative flood protection when catchbasins become clogged by ice, hail or other debris. Overland flow routes may be designed to convey more frequent flows, which can reduce the size of storm pipes and number of catchbasins required for adequate drainage. When Sameng Inc.

9.7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

overland conveyance is used in this way, it should not increase flow rates in downstream systems, so storage is still required in those cases. Stormwater management facilities should be in areas where overland drainage would naturally concentrate. This will make the design of conveyance systems, both above and below ground, easier to plan. 9.5.5

Urban and Rural Cross Sections

The City of Grande Prairie currently has mostly curb-and-gutter road cross sections, with runoff directed towards catchbasins. However, there are some areas with a rural cross section with roadside ditches. Rural cross sections typically occupy more space and require additional maintenance. They are not recommended for future developments. Where developers wish to use primarily overland conveyance, grassed bioswales should be used rather than roadside ditches. Where planned drainage systems will receive extraneous flows from undeveloped lands with rural cross sections, the receiving system should be planned to account for spring runoff volumes from the extraneous basin as an interim condition. For example, downstream wet ponds may have their normal water level temporarily lowered in March and kept low until snow packs have melted. 9.5.6

Other End-of-Pipe Options

Provincial guidelines include other options for water quality treatment that are best combined with stormwater management facilities and/or on lot BMP. These include Oil/Grit separators, sand filters, infiltration trenches, and infiltration basins. These options have limited applicability and are not usually effective on their own, but they may be appropriate as secondary treatment. 9.5.7

Runoff and Storage Estimations

Stormwater facilities and pipes will need to be designed to meet the specific needs of each development, and it is recommended that computer modeling be required to calculate runoff rates and pond storage requirements, though rational method may still be appropriate for sizing upstream pipes and catchbasins. For the purposes of this master plan, pond storage requirements are estimated using a simplified water balance, where Storage = (Runoff â&#x20AC;&#x201C; Discharge) over a 24-hour period. Runoff is based on the new IDF curves, assuming a peak discharge rate of 5 L/s/ha, a storage provision of 500 mÂł/ha will accommodate a 100-year event with a runoff/rainfall ratio of 0.9. This volume is used to estimate volumes for storage ponds.

Sameng Inc.

9.8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

For facilities that are allowed to overflow during extreme events, 250mÂł/ha is used instead. This is approximately equivalent to a 25-year rainfall event over 4 hours and is in line with Alberta Environment guidelines for water quality management. To estimate peak flow rates for sizing sewers, an average travel time of 1 hour was paired with a typical runoff coefficient of 0.6 to yield a rate of 35 L/s/ha. This rate estimate indicates a 1050mm diameter storm sewer is needed to drain a 64-hectare development, without additional storage. The travel time and runoff coefficient are justifiable assuming best management practices for runoff control are used. It is recommended that no more than 64 hectares be drained to a single trunk without additional storage. Land Use 9.6.1

General

The general land use for future development area was outlined in the Municipal Development Plan, as shown in Figure 1-5. See Section 1.3 for more information. Land use will affect the volume, quality, and rate of discharge from runoff, so drainage system requirements will be based partly on the land use within a particular watershed. 9.6.2

Grande Prairie Airport

There are additional constraints for future development around the Grande Prairie Airport. Dry ponds should be designed to drain within 48 hours of storm events and should not include vegetation that would provide habitat for birds. There are two large water features, Hughes Lake and a wetland complex, that would naturally attract birds but cannot be practically removed. More active discouragement of birds (nets, air cannons) are required for the safe operation of the airport however these are outside of the scope of the current master plan. Environmentally Sensitive Areas Riparian corridors, wetlands, and other environmentally significant features were generally assessed for the City of Grande Prairie in 2012. As part of this assessment, areas of high importance were identified based on several factors, including size, vegetation, hydrologic function, and connectivity. These areas, shown in Figure 9-3, occupy large portions of some future development areas, as well as the Bear Creek ravine. Development in the Bear Creek riparian zone will not typically be approved under the Water Act. The limits of development around Bear Creek, as well as around named lakes in Grande Prairie, are shown in Figure 9-3. Within the roughly 6,800 hectares of total land for future development, there is nearly 600 hectares of environmentally sensitive land in the form of wetlands, riparian zones, and

Sameng Inc.

9.9

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

upland vegetation. These areas provide the important eco-system for runoff quality and quantity regulation to the surrounding farmland, as well as habitat for regionally important wildlife, such as swans. The stormwater drainage plan should strive to preserve these sensitive areas, which includes incorporating them into the overall drainage plans. Integration of natural areas into the stormwater management plan is cost effective in that it uses the natural topography to reduce demands for fill, avoids wetland compensation costs, and reduces the constructed storage volume requirements. In addition, maintaining natural riparian corridors provides environmental value, reduced flood risk, and effective visual and sound barriers. ESAs, whether they are actively incorporated into future stormwater plans, will need to be studied to ensure development does not harm the function of the wetland. Weirs and gates may need to be constructed to manage water levels in wetlands where development may increase or decrease runoff to the wetland. Constructed forebays will be required to manage water quality of runoff to some wetlands. Stormwater Quality Current standards for stormwater quality management facilities requires 85% TSS removal of particles 75 microns or greater, as well as regulation of nitrogen and phosphorus concentrations. The use of constructed wetlands, or natural wetland with forebays has been shown to be more effective than wet ponds in both sediment removal and nutrient regulation. Additional water quality targets should be set by watershed area to effectively manage water quality in lakes and streams. For example, contamination containment may be required at potential pollution sources, especially upstream of environmentally sensitive areas. Specific water quality management targets should be determined through biological studies of receiving waterbodies, including specific monitoring requirements based on potential contamination risks. Future Stormwater Management Watersheds An overview of the future stormwater management plan is shown in Figure 9-4. It includes utilizing 29 natural areas for storage and water quality management with 18 constructed forebays, as well as an additional 54 constructed SWMF. Some of these SWMF are included in existing Outline Plans or Area Structure Plans. The future servicing area is separated into 19 watersheds that share common characteristics and/or a single receiving waterbody. Some of these watersheds are further divided into a total of 37 sub-basins with independent outfalls or major road crossings. The sub-basins are summarized in Table 9-2, and the watersheds are described in more detail within the following sections.

Sameng Inc.

9.10

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table 9-2: Summary of Watersheds in Future Servicing Plan

Sameng Inc.

9.11

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.9.1

City of Grande Prairie

Watershed “A” – Bear Lake Basin

Watershed A, shown on Figure 9-5, consists of lands that naturally drain towards Bear Lake. As Bear Lake has an open water area of over 31 km², it provides a significant volume of storage for the immediate basin area. Stormwater management should be designed primarily for water quality, and in connection with conveyance infrastructure to discharge into the lake. There are two ESAs at the boundary of the City that serve as natural collection points for drainage. These should be enhanced to ensure water quality performance. An additional wet pond is recommended to manage flows more distant from the natural storage, to reduce the size of conveyance required and protect downstream natural areas. Watershed “A” Receiving Waterbody Bear Lake Basin Area 240 ha. Extraneous Basin Area N/A Land Use Residential ESA 2 @ 10.4 ha Additional Ponds 1 44,000 m³ Natural Storage Volume

Sameng Inc.

9.12

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.9.2

City of Grande Prairie

Watersheds “B” and “C’ – Northwest Bear Creek

This land, shown on Figure 9-5, is planned for residential development, north of Highway 43X, and will discharge into Bear Creek. No ESAs were identified in this watershed (except for Bear Creek), so constructed SWMF will be required to control discharge to the prescribed 5 L/s/ha. Proposed ponds are shown at natural low spots on the land, or at existing dugouts that may be expanded. Note that the number of ponds for these watersheds is increased from the previous master plan, to limit the length of travel to ponds to 800 metres. Ponds may be consolidated if adequate conveyance is provided. Watershed “B” Receiving Waterbody Bear Creek Basin Area 314 ha. Extraneous Basin Area N/A Land Use Residential ESA None Additional Ponds 4 Natural Storage Volume Watershed “C” Receiving Waterbody Bear Creek Basin Area 231 ha. Extraneous Basin Area 400 ha Land Use Residential ESA None Additional Ponds 3 Natural Storage Volume

Sameng Inc.

9.13

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.9.3

City of Grande Prairie

Watershed “D” – Highway 43X

This watershed is comprised of lands draining towards the Highway 43X ditches and will use those ditches to avoid the construction of additional outfalls to Bear Creek. An ESA (D1) exists in this watershed, as shown in Figure 9-5, south of an existing country residential community. The plans for this watershed include 2 large constructed ponds (D2, D3) that are located at active borrow pits for the construction of Highway 43X. It is proposed that these pits be converted and enhanced to provide storage of runoff from the highway and surrounding developments. Ponds and conveyance in this area should work in connection with the functional drainage of Highway 43X. Watershed “D” Receiving Waterbody Bear Creek Basin Area 310 ha. Extraneous Basin Area N/A Land Use Commercial ESA 1 @ 8.15 ha Additional Ponds 2 36,000 m³ Natural Storage Volume

Sameng Inc.

9.14

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.9.4

City of Grande Prairie

Watershed “E” – South of Highway 43X

This watershed has extensive ESA areas that lead to Bear Creek, as shown in Figure 9-5. Natural depressions in these areas have sufficient capacity to store 100-year flows from residential or light commercial development, while controlling discharge to the current standard 5 L/s/ha. A watershed study is recommended to establish the flood limits and setbacks from the natural wetlands. Additional improvements will be required along the drainage paths connecting the ESAs, to control water levels, establish discharge rates, and manage water quality. The existing connectivity between the natural areas should be maintained as much as possible. Defined setbacks from development will create a drainage parkway connecting the natural areas. The drainage parkway should include filter strips and/or forebays within the setback to receive flows from the local conveyance system. Watershed “E” Receiving Waterbody Bear Creek Basin Area 772 ha. Extraneous Basin Area 122 Land Use Commercial/Residential ESA 6 @ 95.25 ha Additional Ponds 430,000 m³ Natural Storage Volume

Sameng Inc.

9.15

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.9.5

City of Grande Prairie

Watershed “F” – Hermit Lake

As shown in Figure 9-6, Hermit Lake is large enough to provide an adequate outlet for the small watershed within the City. The establishment of riparian zones and/or forebays on the shore of the lake are required to manage water quality of runoff into the lake. These should be designed primarily to protect the lake from pollution and erosion. Retention storage would be provided by the lake itself. The use of overland drainage options (bioswales, filter strips, etc.) would reduce the need for surface dispositions for new outlets into Hermit Lake. Watershed “F” Receiving Waterbody Hermit Lake Basin Area 170 ha. Extraneous Basin Area N/A Land Use Commercial/Residential ESA 1 @ 4.59 ha Additional Ponds 0 23,000 m³ Natural Storage Volume

Sameng Inc.

9.16

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.9.6

City of Grande Prairie

Watershed “G” – Flyingshot Lake/Wetland

Flyingshot Lake (G0 on Figure 9-6) and the upstream wetland area is potentially a suitable outlet, to be verified by a watershed study. In any case, the lake will provide a large amount of potential storage volume, before continuing into Flyingshot Creek and Bear Creek. The storage and discharge requirements of development in this basin should be based on the capacities of drainage routes to the wetland. There is a mostly continuous band of ESA/marshland between Hermit Lake and the wetland north of Flyingshot Lake. Air photos and contour maps indicate that this area is frequently flooded and could be converted to an effective drainage parkway. Establishing the riparian zone and overland channels would provide water quality and erosion control for most of the runoff west of the airport. Hydraulic and biological assessment of the existing low area will help in establishing the parkway and flood limits. Development below the historic flood limit should remain restricted. The construction of Hydraulic structures at road crossings would be a major cost of establishing the parkway, including Highway 43X to control flow rates and protect the downstream channels. Inflow channels through the riparian zone would need to be designed to control erosion and provide opportunities to contain potential pollution sources. These structures may be built in stages, provided downstream conditions are considered. The riparian zone also provides opportunity for enhancement for walking and biking trails, potentially crossing Highway 43X and connecting Flyingshot Lake with Hermit Lake. The lands surrounding the airport, and planned developments to the south and east are also planned to discharge into Flyingshot Lake. Because of proximity to the airport, dry ponds are recommended to control for water quality, and to reduce the size of conveyance infrastructure. Where possible, discharge should be limited based on the capacity of existing ditches and culverts to Flyingshot Lake and the upstream wetland. Watershed “G” Receiving Waterbody Flyingshot Lake Basin Area 1,620 ha. Extraneous Basin Area N/A Land Use Commercial ESA 6 @ 151 ha Additional Ponds 11 603,000 m³ Natural Storage Volume

Sameng Inc.

9.17

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.9.7

City of Grande Prairie

Watershed “K” – Kensington Development

The Kensington outline plan, as shown in Figure 9-6, identifies four (4) new ponds, and the expansion of existing ponds west of 116 Street. The expanded ponds, as well as pond K1 discharge into the existing storm sewers at 116 Street. These ponds should control as much flow as possible, up to a zero-discharge volume of 1,000m³/hectare, as the downstream system has capacity deficiencies discussed in previous sections of this report. Real-time control may be necessary to ensure proper function of the ponds given the constraints on the existing system. The other ponds in this watershed will discharge by ditch into Flyingshot Lake. These ponds should be designed primarily for water quality, and overland flow paths should be identified and established to Flyingshot lake. South of the Kensington Development, adjacent to Flyingshot Lake, existing forebays on the lake should be maintained and enhanced for water quality and erosion protection; Flyingshot Lake itself is the storage facility for this area. Watershed “K” Receiving Waterbody Flyingshot Lake/Existing Basin Area 228ha. Extraneous Basin Area N/A Land Use Residential ESA None Additional Ponds 5 Natural Storage Volume

Sameng Inc.

9.18

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.9.8

City of Grande Prairie

Watershed “H” – Hughes Lake

The natural watershed of Hughes Lake, as shown in Figure 9-7, should be maintained as much as possible, and the riparian zone of Hughes Lake should be defined based on biological and hydraulic assessment. The riparian area of Hughes Lake contains enough volume to store post development runoff without the need for additional storage. Forebays should be constructed within the setback around the lake to manage water quality of runoff. A single pond (H1) is identified at an existing dugout that could be incorporated into the stormwater management plan. The discharge rate from Hughes Lake should be kept close to existing conditions, as determined by a watershed study. If additional storage is required to maintain water levels within a certain range, the proposed forebays should be expanded to provide the necessary volume. Hughes Lake requires waterfowl management to discourage birds that may interfere with the airport. Maintaining a single large facility will be easier than multiple smaller ponds. Watershed “H” Receiving Waterbody Hughes Lake/Bear Creek Basin Area 493ha. Extraneous Basin Area N/A Land Use Commercial ESA Lake: 160 ha Additional Ponds 1 Natural Storage Volume

Sameng Inc.

9.19

Storm Drainage Master Plan 2018 Final Report (Revision 1)

9.9.9

City of Grande Prairie

Watershed “I” – North of Airport

As shown on Figure 9-7, the large wetland complex (I5) is an environmentally sensitive area that consists of continuous marshland, which currently receives drainage from the north part of the airport. The existing wetland and riparian zone can provide adequate storage volume for the watershed, and there is an existing drainage channel between the wetland and Bear Creek, running through another ESA (I6). This channel should be upgraded to a drainage parkway with hydraulic structures to control flow rates and sediment transfer, and to utilize potential storage in the low areas of I6. Using the existing drainage corridor will avoid the need for a new outfall to Bear Creek, but the condition and capacity of the existing outfall will need to be verified. Lot-level flow and water quality management would be appropriate for this watershed to reduce the costs of local conveyance infrastructure. Due to the proximity to the airport, measures to discourage birds are necessary at this wetland. Watershed “I” Receiving Waterbody Bear Creek Basin Area 580ha. Extraneous Basin Area N/A Land Use Commercial ESA 2 @124.5 ha Additional Ponds 0 410,000 m³ Natural Storage Volume

Sameng Inc.

9.20

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

9.9.10 Watershed “J” – Linear Drainage Parkway. Though not identified as a priority environmental area, there is a large depression and existing drainage channel (J1) that serves this watershed, as shown in Figure 9-7. This corridor should be upgraded to a drainage parkway to control flows, improve water quality, and provide environmental enhancement. This will require the construction of hydraulic structures along the flow path to limit flows to Bear Creek to 5 L/s/ha. Using the existing drainage corridor may avoid the need for a new outfall to Bear Creek. Watershed “J” Receiving Waterbody Bear Creek Basin Area 173 ha. Extraneous Basin Area N/A Land Use Residential ESA 1 @15.78 ha Additional Ponds 96,000 m³ Natural Storage Volume

Sameng Inc.

9.21

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

9.9.11 Watershed “V” – Hidden Valley and Northwest ASPs This watershed is covered by the Hidden Valley, Northwest, and Arbor Hills Area Structure Plans, as well as the West Terra Outline Plan as shown in Figure 9-7. The Northwest plan indicates a new storm trunk (now partially constructed) along the southern edge of the development, leading to a recently completed outfall near the Grande Prairie Regional Hospital. Ponds are located along the trunk to control discharge rates to 5 L/s/ha. In addition to these ponds, overland flow routes should be established to direct overflows through the ponds. The Hidden Valley ASP identified a number of ponds, some already in service. Some of these ponds are proposed within the Bear Creek riparian zone. It is recommended that these ponds be moved out of the riparian zone and consolidated where possible to reduce the number of new outfalls. Watershed “V” Receiving Waterbody Bear Creek Basin Area 498 ha. Extraneous Basin Area 448 Land Use Commercial/Residential ESA None Additional Ponds 10 Natural Storage Volume

Sameng Inc.

9.22

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

9.9.12 Watershed “L” – Crystal Lake Basin As shown on Figure 9-8, a part of the future development area drains naturally towards the Crystal Lake basin. A stormwater management facility should control flows based on the capacity of the pipe crossing Highway 670. Water quality and storage are effectively managed in the downstream wetland and Crystal Lake. Alternatively, lot-level runoff management, or oversizing of the pipe across Highway 670 could eliminate the need for a central stormwater management facility, subject to verification by a watershed study. Watershed “L” Receiving Waterbody Crystal Lake Basin Area 21 ha. Extraneous Basin Area 0 Land Use Commercial ESA None Additional Ponds 1 Natural Storage Volume

Sameng Inc.

9.23

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

9.9.13 Watersheds “M” and “N” – Northeast ASP The Northeast Area Structure plan includes most of these watersheds, as shown on Figure 9-8. Watershed “M” is planned for commercial development, similar to existing Clairmont developments. A large ESA collects runoff from this watershed. Establishing the riparian area around the wetland portion of the ESA (M7) will provide storage for the entire watershed, while ponds and forebays will manage local runoff and protect the wetland from excessive velocities and potential pollution. Overland drainage routes between the constructed ponds and the wetland will be important for conveying 100year flow rates. At the northern boundary of the City, an extraneous watershed flows to an existing wetland area. This area will spill over into M7 and south when full. A hydrological assessment of the surface and groundwater should be done to determine the effective extraneous flows into the City portion of this watershed. The wetland at M7 will discharge into the larger complexes south of Highway 670. A control structure should be installed at the southern tip of the ESA to manage water levels in the wetland. Watershed “M” Receiving Waterbody Unnamed Creek Basin Area 371 ha. Extraneous Basin Area 100 ha Land Use Commercial ESA 1 @ 22.96 ha. Additional Ponds 3 140,000 m³ Natural Storage Volume South of Highway 670, a large wetland complex (N1, N2, N3) is identified as ESA. This area has very flat topography, with poor overland drainage. The Kingsgate Landing Outline Plan identifies pond N1 to replace part of the existing wetland, and it provides storage at greater depths than the natural contours allow. It is recommended that the wetland complex be avoided as much as possible and enhanced for erosion and sedimentation control at inlets. The storage and water quality performance of the wetland is unlikely to be improved through disruption, and the land gained by shrinking the wetland area would be at risk of flooding due to inadequate drainage. Hydraulic and Ecological analysis on the unnamed creek downstream of the wetland complex is recommended to determine appropriate release rates and water quality targets for development in these watersheds.

Sameng Inc.

9.24

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Watershed “N” Receiving Waterbody Unnamed Creek Basin Area 281 ha. Extraneous Basin Area 471 ha Land Use Residential ESA 2 @ 51.45 ha. Additional Ponds 1 160,000 m³ Natural Storage Volume

Sameng Inc.

9.25

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

9.9.14 Watershed “P” – Unnamed Creek Runoff in this basin, shown in Figure 9-8, concentrates to natural low areas and wetlands, before draining through an unnamed creek tributary to Bear Creek, running through Grande Prairie County. This watershed also includes extraneous flows that pass-through City lands. Establishing and riparian zone of these wetlands and the creek could effectively manage downstream flows in the creek, to be verified by a hydrologic assessment of the overall basin. Expanding the riparian zone (P4, P5) will add conveyance and storage to other areas. Establishing adequate setbacks from the existing wetlands will be important in providing effective flood prevention for developments in this area. Hydraulic structures and erosion protection may be required in sections of the unnamed creek, in both City and County reaches of the creek. Watershed “P” Receiving Waterbody Unnamed Creek Basin Area 856 ha. Extraneous Basin Area 437 ha Land Use Commercial ESA 6 @ 96.9 ha Additional Ponds 3 428,000 m³ Natural Storage Volume

Sameng Inc.

9.26

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

9.9.15 Watershed “Q” – West Carriage Lanes The West Carriage Lanes Outline Plan, as shown in Figure 9-9, has proposed a linear drainage parkway, replacing the existing wetland complex. The West Carriage Lane subdivision is a continuation of development on the County side and includes the expansion of an existing pond/wetland (Q5). This facility also receives some of the drainage basin on the county side. The developer-proposed drainage plan also includes shrinking the existing wetland at Q1, supplying the same volume of storage, though the disruption of the wetland has not yet been approved by Alberta Environment. As an alternative, the wetland could be preserved and enhanced for storage, which may reduce flood concerns downstream in the Woody channel/creek basins. The current concept limits discharge from this watershed to 5 L/s/ha, in order to preserve capacity in the Woody Channel basin. It is recommended that this requirement be kept. Watershed “Q” Receiving Waterbody Woody Channel/Creek Basin Area 285 ha Extraneous Basin Area 27 ha Land Use Residential ESA 1 @ 22.1 ha Additional Ponds 4 98,000 m³ Natural Storage Volume

Sameng Inc.

9.27

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

9.9.16 Watershed “R” – Woody Channel/84 Street The watershed south of 100 Avenue, as shown in Figure 9-9, drains south to Woody channel. Facilities in this watershed must store 100-year runoff volumes, and limit discharge to 5 L/s/ha due to limited capacity in the downstream system. There is also concern that uncontrolled runoff from County lands to Woody Channel south of 68 Avenue are causing flooding along the City boundary. Upgrades to Woody Channel inside the City may be required to address these issues. Watershed “R” Receiving Waterbody Woody Channel/Creek Basin Area 186 ha Extraneous Basin Area 352 ha Land Use Residential ESA Additional Ponds 3 Natural Storage Volume

Sameng Inc.

9.28

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

9.9.17 Watershed “W” – Wood Lake Basin The watershed for Wood Lake, as shown in Figure 9-9, naturally drains through a significant Riparian zone. As this watershed develops, water quality enhancements (forebays) should be constructed at outfall locations. Additional storage beyond that required for water quality is not required in this watershed, as these volumes can be effectively managed by the lake itself. Watershed “W” Receiving Waterbody Wood Lake Basin Area 214 ha. Extraneous Basin Area N/A Land Use Residential ESA Lake shore Additional Ponds 107,000 m³ (in Lake) Natural Storage Volume

Sameng Inc.

9.29

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Implementation and Costs 9.10.1 Watershed Studies Watershed studies should be conducted early, especially for those areas that will have outlets other than Bear Creek. Release rates and water quality requirements should be set by watershed, rather than ‘one-size-fits-all’ values. These watershed studies will also delineate floodplains and riparian areas and set encroachment limits for development. Watershed studies should include the following; • Delineation of historic flood levels and flow rates • Analysis of pre-development runoff characteristics • Analysis of water level fluctuations in wetlands, to determine normal ranges and rates of increase/decrease. • Hydrologic and Biological assessment of all wetlands. • Identification of habitats for fish, birds, amphibian and other species. • Identification of pollution limits and recommendations for water quality. These studies will be important during the implementation phase of the stormwater master plan and may require approval by Alberta Environment. The guiding principals of these will be needed by developers for design of their subdivision and overall integration of individual developments. 9.10.2 Public Easements and Interim Drainage Plans This master plan consists of centralized facilities that may ultimately serve multiple developments. In some cases, naturalized drainage parkways will cross property lines and will require the registration of easements to provide continuous facilities. Ideally, complete facilities should be commissioned in advance of development, and easements to allow access can be established to avoid conflicts. Developers should be encouraged to avoid blocking natural drainage pathways. 9.10.3 Value Added The use of wetlands and drainage parkways provides the opportunity for recreational amenities. Though not necessary for stormwater management, these features may be incorporated into the design of hydraulic structures. For example, a control structure may include a pedestrian bridge and bird-watching platform. Incorporating these kinds of features in the preliminary stages of design will help provide greater value. The Grande Prairie area is the primary habitat for Trumpeter Swans. Landowners are encouraged to help preserve this endangered species through provincial, federal, and nongovernment programs. Stormwater plans can help these efforts by identifying swan habitats and creating new habitat in well-managed drainage parkways and constructed wetlands.

Sameng Inc.

9.30

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Stakeholder and Public Consultation A stakeholder open house was held on May 9, 2018 to present the stormwater master plan concept to prospective developers, their consultants, as well as other utility providers and City departments. A summary of this open house is included in Appendix F. A public open house was held on September 11, 2018 to present the stormwater master plan improvement concepts and future development concepts to the general public.

Sameng Inc.

9.31

ROADWAY CB 25 YEAR / 4 HOUR EVENT

STORM SEWER

OVERLA ND FLOW

NWL

5YR DESIGN

FOREBAY

PATHWAY

CHANNEL

FLOOD LEVEL NORMAL LEVEL

SCENARIO 1: ADJACENT TO SUITABLE OUTLET

Prepared By:

OVERLA ND FLOW

ROADWAY CB STORM SEWER

5YR DESIGN

FOREBAY

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

PATHWAY

CHANNEL

Client:

FLOOD LEVEL NORMAL LEVEL Project:

SCENARIO 2: FAR AWAY FROM SUITABLE OUTLET

Storm Drainage Master Plan 2018 Title:

Stormwater Management Concept Natural / Constructed Components

Scale:

Figure:

N.T.S.

9-1

Reinforced Trails Sections allow for overland flow crossings

Grassed Bioswales Behind houses slow runoff and improve water quality

Storm Sewer Collect street runoff up to 1:5 year peak and direct it to forebay

Native Turf/Grasses Provide upland vegetation

Drainage Parkway Follows natural drainage paths enhanced to provide storage and erosion protection.

Wetland Outlet Into storm pipes or enhanced channel designed to repel blockages

Enhanced Drainage Channel Mimics natural brook, flanked by willows and reeds with a frequently flooded bank Channel can be made too allow fish habitats

Wetland Complex Incorporates natural topography and wet features as much as possible

Frequently Flooded Area Contains 1:5 year runoff event

Deep Pond Provides stability for ecology during drought periods and clarifies outflows

Infrequently Flooded Area Contains 100-year runoff event Trails and structures located in the flood area should be designed to withstand the wet conditions

Aquatic Safety Bench Shallow marsh area separates deep water areas from shore

Filter Vegetation Strip Surrounds the parkway to protect the wetland and remove contaminants from surface flow

Lower Marsh Varying water depths for diverse vegetation and habitats High Marsh Emergent vegetation (reeds, grasses) grow here to stabilize the shoreline and provide habitat for nesting birds and improve water quality filters and absorbers pollutants Wetland Micro Topography Shallow grade to provide internal complexity to the wetland

Enlarged Bioswales Convey overflows from other areas/ponds, providing water quality improvement and wildlife corridors

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Project: Forebay Receivers inflows, reduces velocities and traps sediment/floatable

Enlarged Forebay Stores 1:2 year runoff volumes or more from upstream basins to buffer fluctuations in wetland water levels

Storm Trunk From other areas carrying up to 5L/s/Ha

Submerged Pipes Or other structures control flow from forebays to wetland or channel Overflows crest weirs or reinforced trail sections

Storm Drainage Master Plan 2018 Title:

Naturalized Drainage Parkway Overview Scale:

Figure:

N.T.S.

9-2

LEGEND CITY BOUNDARY) ENVIRONMENTALLY SENSITIVE AREAS

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Project:

Storm Drainage Masterplan 2018 Title:

Environmentally Sensitive Areas Scale:

Figure:

N.T.S.

9-3

BEAR CREEK

BEAR LAKE

HIGHWAY 2

A(i)

LEGEND CLAIRMONT LAKE

CITY BOUNDARY PROPERTY LINE STORMWATER MANAGEMENT FACILITY (WET)

STORMWATER MANAGEMENT FACILITY (DRY)

LAKE

B2 C3

HIGHWAY 43X

B3 A1

MAJOR OVERLAND FLOW DIRECTION

HIGHWAY 43

BASIN BOUNDARY

E(iii)

SUB BASIN BOUNDARY D(ii) D3

E(ii)

V10 AR

G(i) HUGHES LAKE

HIGHWAY 43X

V(i)

V12

G12

V13

G(iii) G6

HIGHWAY 43

G14

G16

G10

G15

20 SILVER POINTE

G(v)

K(ii) K2 K3 K4

K(iii)

PROPOSED FOREBAY P9

116 AVENUE Q(i)

Q2 Q(ii) CARRIAGE

29 LANE ESTATES

RESERVOIR

84 AVENUE

20 W(i)

W1 WOOD LAKE

W(ii)

100 AVENUE

PROPOSED SWMF (BY DEVELOPER)

P11

K(i)

G17

31 CRYSTAL LAKE

116 STREET

G13 HIGHWAY 43

PROPOSED SWMF

PROPOSED WETLAND / DRAINAGE PARKWAY

P6 P10

OUTLINE PLAN - 1224ha IN DEVELOPMENT

3 P4

P(iii)

EK RE

G11

C AR BE

G(iv)

G7 G4

P2 SECONDARY HIGHWAY 670

I4 G(ii)

34 V5

V(ii)

FUTURE HIGHWAY

M1 132 AVENUE

V11

M2 L1

V9 V(iii)

P(ii)

V(iv)

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

W3 SANDRY RIDGE ESTATES

EXISTING FOREBAY

EE K BE AR

SPRUCEWOOD PARK

HIGHWAY 40

WILLOWOOD ESTATES

10 Project:

TAYLOR ESTATES

Storm Drainage Master Plan 2018

REEK

BEAR C

WEDGEWOOD

Title:

WATER TREATMENT PLANT

RESOURCES ROAD

Client:

68 AVENUE

FLYINGSHOT LAKE

DRAINAGE BASIN ID

AREA STRUCTURE PLAN

EE CR

I I1

A(ii)

P(i)

ALBINATI INDUSTRIAL

EXISTING HIGHWAY

92 STREET

HERMIT LAKE

DEVELOPMENT LIMIT HIGHWAY 43

E(i)

BASIN DRAINING INTO EXISTING STORM SYSTEM

D(i)

E(iv)

100 STREET

84 STREET

HIGHWAY 43

A(ii)

HIGHWAY 40 108 STREET

Future Development Plan Overview

BEAR CREEK

3 Scale:

Figure:

9-4

LEGEND CITY BOUNDARY

A(i)

BEAR LAKE

BEAR CREEK

PROPERTY LINE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY)

LAKE MAJOR OVERLAND FLOW DIRECTION

BASIN BOUNDARY SUB BASIN BOUNDARY BASIN DRAINING INTO EXISTING STORM SYSTEM

B2 A(ii)

DRAINAGE BASIN ID DEVELOPMENT LIMIT

EXISTING HIGHWAY

FUTURE HIGHWAY

AREA STRUCTURE PLAN

E(iii)

OUTLINE PLAN PROPOSED WETLAND / DRAINAGE PARKWAY PROPOSED SWMF

D(ii)

PROPOSED FOREBAY

A(ii)

E(iv) D3 E(ii)

PROPOSED SWMF (BY DEVELOPER)

D(i)

E(i)

E3 F1

4 J Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Project: D2, D3 - BORROW PIT FOR HIGHWAY 43X

Storm Drainage Master Plan 2018 Title:

Future Development Plan North West Scale:

Figure:

N.T.S.

9-5

ES GH

i) G(

3 Y4

iv) G(

29 G13

G11

36 G1

H RT

G10 G9

RT P PO IAL O R I A TR US IND

G15

SUB BASIN BOUNDARY

VE SIL

DRAINAGE BASIN ID DEVELOPMENT LIMIT

EXISTING HIGHWAY

FUTURE HIGHWAY

i) K(i G17

IN NS

O GT

AREA STRUCTURE PLAN OUTLINE PLAN

ii) K(i

PROPOSED WETLAND / DRAINAGE PARKWAY PROPOSED SWMF PROPOSED SWMF (BY DEVELOPER) PROPOSED FOREBAY

G TIN AY S I EX REB KE FO T LA

HO GS N I

G6 G5

v) G(

MAJOR OVERLAND FLOW DIRECTION BASIN BOUNDARY

21 K(i)

O RP

LAKE

A(ii)

G16

STORMWATER MANAGEMENT FACILITY (DRY)

BASIN DRAINING INTO EXISTING STORM SYSTEM

4 AY

STORMWATER MANAGEMENT FACILITY (WET)

H HIG

S WE

G14

SP TA

HW G I H

G12

ii) G(

iii) G(

M ER

KE LA

F1 IT

CITY BOUNDARY PROPERTY LINE

1 H

LEGEND

3 V1

WE TH

T EE R T 6S

) V(i

Y4 A HW HIG

P AS T S

ET RE T 8S

) E(i

Y FL

24 18

8 Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Project: K1, K2, K3, K4 - KENSINGTON OP

Storm Drainage Master Plan 2018 Title:

G13 - NORTHWEST ASP G14, G15, G16 - AIRPORT INDUSTRIAL OP

Future Development Plan South West Scale:

Figure:

N.T.S.

9-6

LEGEND

E(i)

CITY BOUNDARY

PROPERTY LINE

STORMWATER MANAGEMENT FACILITY (WET)

STORMWATER MANAGEMENT FACILITY (DRY)

LAKE MAJOR OVERLAND FLOW DIRECTION

V10

H5 H

ARBOR V(iv) HILLS ASP

BASIN BOUNDARY SUB BASIN BOUNDARY BASIN DRAINING INTO EXISTING STORM SYSTEM

A BE

HUGHES LAKE H2

K EE CR

I I6

A(ii)

V11

V(iii)

DEVELOPMENT LIMIT EXISTING HIGHWAY

HIDDEN VALLEY ASP

FUTURE HIGHWAY AREA STRUCTURE PLAN

OUTLINE PLAN

HIGHWAY 43X

PROPOSED WETLAND / DRAINAGE PARKWAY

34 V5

V(ii)

DRAINAGE BASIN ID

PROPOSED SWMF PROPOSED SWMF (BY DEVELOPER) PROPOSED FOREBAY

G(ii)

G(iv)

V(i)

NORTHWEST ASP

WEST TERRA OP

G11

V12 V13

G12

RESERVOIR

NORTHWEST ASP

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

V1, V2 - WEST TERRA OP V3 - EXISTING V4, V5, V6, V7, V8, V9, V11 - HIDDEN VALLEY ASP V10 - ARBOR HILLS ASP V12, V13 - NORTHWEST ASP

Project:

Storm Drainage Master Plan 2018 Title:

Future Development Plan West Scale:

Figure:

N.T.S.

9-7

LEGEND CITY BOUNDARY

HIGHWAY 43

PROPERTY LINE

P(i)

ALBINATI INDUSTRIAL

P(ii)

STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE

MAJOR OVERLAND FLOW DIRECTION

BASIN BOUNDARY

A(ii)

P5 M2

DRAINAGE BASIN ID DEVELOPMENT LIMIT

EXISTING HIGHWAY

M1 L1

BASIN DRAINING INTO EXISTING STORM SYSTEM

M7 L

SUB BASIN BOUNDARY

FUTURE HIGHWAY

132 AVENUE N KINGSGATE LANDING OP

SECONDARY HIGHWAY 670 P(iii)

P10

AREA STRUCTURE PLAN

OUTLINE PLAN

P11

PROPOSED WETLAND / DRAINAGE PARKWAY

PROPOSED SWMF

100 STREET

PROPOSED SWMF (BY DEVELOPER)

PROPOSED FOREBAY

CRYSTAL LAKE

116 AVENUE Q2

Q(i)

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Project:

Storm Drainage Master Plan 2018

N1 - KINGSGATE LANDING OP Title:

Future Development Plan North East Scale:

Figure:

N.T.S.

9-8

LEGEND CITY BOUNDARY PROPERTY LINE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE

BASIN BOUNDARY SUB BASIN BOUNDARY

SANDRY RIDGE ESTATES

Q(ii)

WOOD LAKE

CARRIAGE LANE ESTATES

MAJOR OVERLAND FLOW DIRECTION

BASIN DRAINING INTO EXISTING STORM SYSTEM A(ii)

DEVELOPMENT LIMIT

EXISTING HIGHWAY

FUTURE HIGHWAY

W1 W(i)

W(ii)

AREA STRUCTURE PLAN OUTLINE PLAN

TAYLOR ESTATES

WEST CARRIAGE LANE OP Q3

WILLOWOOD ESTATES

DRAINAGE BASIN ID

PROPOSED WETLAND / DRAINAGE PARKWAY PROPOSED SWMF PROPOSED SWMF (BY DEVELOPER)

84 STREET

PROPOSED FOREBAY

FIELDBROOK OP

Q(i)

SIGNATURE FALLS OP

SUMMERSIDE EAST OP SUMMERSIDE OP

BEAR CREEK

MEADOWVIEW ASP

RESOURCES ROAD

Prepared By:

R1, R2 - MEADOWVIEW ASP R3 - FIELDBROOK OP

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Q1, Q2, Q3, Q4, Q5 - WEST CARRIAGE LANE OP

Project:

Storm Drainage Master Plan 2018 Title:

Future Development Plan South East Scale:

Figure:

N.T.S.

9-9

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

10.0 Conclusions and Recommendations • The City has seen a 34% population growth in the last decade, and recently annexed more than 6,300 ha of land to bring the total area of the City to nearly 13,700 ha. • The current City of Grande Prairie servicing standards are mostly in conformance with Provincial guidelines for stormwater drainage design, as well as other Alberta municipalities. Some modifications to those standards were recommended, including the update of the rainfall IDF curves and design rainfall time series. • A comprehensive review and inventory of the existing storm drainage system was completed and is summarized in the report. Of note, the City has 226 km of storm pipes, 97 storm outfalls and 43 stormwater management facilities. It is recommended that the City develop a comprehensive asset management system and drainage infrastructure inventory to have a better database and understanding of their drainage assets. It is also recommended that the City completes an outfall condition assessment study for all their outfalls (not just the ones in Bear Creek). • The City currently has three rainfall gauges and four flow monitoring gauges. It is recommended that the City add two more rainfall gauges and two more flow monitoring gauges. Two water quality gauges are also recommended to be installed. A comprehensive assessment of the City rainfall and flow monitoring gauges was completed. The extreme August 2, 2016 rainfall event, which caused substantial flooding in the City, was recorded as a 325-year 1-hour duration event at one of the gauges. • A comprehensive dual-drainage hydraulic computer model was developed using the DHI Mike Urban software. This model was used to provide a better understanding of the drainage system performance and deficiencies under extreme rainfall events. The modeling results correlate well with flow monitoring data and known flood risks areas. This model should be continuously updated as the City continues to grow and the drainage system is improved, and further calibrated using additional rainfall and flow monitoring data. • Eleven main areas were identified to be at an elevated risk of flooding during a 100year storm event, due to lack of capacity in the storm sewer combined with a poor major drainage system (i.e. overland drainage). Approximately 20% and 46% of manholes in the City are surcharged to grade during a 5-year storm event, and 100year storm event respectively. Approximately 10% of roadways in the City may see ponding depths of 35cm or greater during a 100-year storm event. • Drainage improvements were conceptualized for developed areas of the City that are at a higher risk of flooding, with a goal to achieve a 100-year level of flood protection. They were grouped into five major projects totalling $98.5M. They focus on reducing, diverting and conveying flows away from the flood-prone areas. Due to the high costs of these upgrades and the large timeframe that would be required to construct them, it is recommended that additional conceptual studies be completed to further refine the

Sameng Inc.

10.1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

improvements for these at-risk areas and prioritize the improvements such that an enhanced level of flood protection (say 1:25-year) can be provided for all flood-prone areas in the short-term and at a lower cost. â&#x20AC;˘ The recommended Stormwater Master Plan identified nineteen (19) watersheds and 34 sub-basins in the future servicing area. Hydrologic and environmental studies for these watersheds should be conducted early to identify opportunities for utilizing and protecting environmentally valuable areas. Setbacks and rights-of-way for natural and artificial stormwater management facilities and drainage parkways should be coordinated with landowners and developers as early in the development process as possible. â&#x20AC;˘ To reduce the environmental impact and cost of stormwater management facilities, the stormwater master plan focuses on preserving, enhancing, and utilizing existing environmentally important areas for stormwater retention. A total of 29 natural areas were identified for significant stormwater retention. An additional 54 stormwater management facilities were identified, mainly in areas where natural depressions are sparse. Constructed forebays on natural wetlands and lakes are identified to preserve water quality and control peak discharges, while the strict requirement to restrict 100year peak runoff to 5 L/s/ha is relaxed based on individual watershed needs. â&#x20AC;˘ The stormwater master plan and subsequent watershed studies may be submitted for approval under the Water Act. This voluntary submission would make the approval process easier for potential developers, as some individual approvals would not be required for stormwater management plans that conform to the master plan.

Sameng Inc.

10.2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Appendix A: Design Rainfall Assessment Memo (February 20, 2018)

Sameng Inc.

1500 Baker Centre, 10025-106 Street Edmonton, AB T5J 1G3 Phone: (780) 482-2557 Fax: (780) 482-2538 maxime.belanger@sameng.com www.sameng.com

February 20, 2017

Our File: 1293

City of Grande Prairie Engineering Services 1st Floor, 10205 98 Street Grande Prairie, AB T8V 2E7 Attention: Re:

Richard Sali Design & Environmental Supervisor

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

Dear Mr. Sali, In an attempt to confirm whether the City’s current IDF curves are representative, Sameng reviewed rainfall data from many rainfall gauges in the vicinity of the City of Grande Prairie. Through this review, it was found that the City’s IDF curves are underestimated and are not conservative. IDF curves with higher intensity were developed and are recommended to be implemented. Furthermore, the City’s synthetic design rainfalls were reviewed. Recommendations to modify or completely change some of these synthetic rainfall distributions were made. This 74-page memo (excluding this letter and including Appendix A) provides a comprehensive summary of the design rainfall assessment that led to these conclusions. Sincerely,

Maxime Bélanger, M.Sc., P.Eng. Municipal / Water Resources Engineer

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table of Contents Table of Contents .................................................................................................................. 1 List of Figures ........................................................................................................................ 1 List of Tables ......................................................................................................................... 2 1.0

Design Rainfall Assessment ......................................................................................... 4 Background ............................................................................................................................. 4 Review of IDF Curves .............................................................................................................. 5 1.2.1 Rainfall Data Collection and Compilation ............................................................................... 5 1.2.2 Frequency Analysis – Select Stations .................................................................................. 13 1.2.3 Frequency Analysis – All Stations Combined ....................................................................... 15 1.2.4 Development of New City of Grande Prairie IDF Curves ..................................................... 16 1.2.5 Comparison of New IDF Curves with Current IDF Curves ................................................... 20 1.2.6 Comparison of New IDF Curves with City of Edmonton IDF Curves .................................... 21 1.2.7 IDF Curves – Conclusions and Recommendations .............................................................. 22 Synthetic Design Rainfalls Events ......................................................................................... 23 1.3.1 Background .......................................................................................................................... 23 1.3.2 Chicago Distribution ............................................................................................................. 25 1.3.3 AES Distribution (Atmospheric Environment Services) ........................................................ 34 1.3.4 SCS Distribution (U.S. Soil Conservation Services) ............................................................. 37 1.3.5 Huff Distribution .................................................................................................................... 44 1.3.6 Synthetic Design Rainfalls – Conclusions and Recommendations ...................................... 61

List of Appendices Appendix A: Gumbel Distribution for Various Rainfall Stations

List of Figures Figure 1: Current City of Grande Prairie IDF curves ............................................................. 4 Figure 2: Location of Selected Rainfall Gauges in Proximity of City of Grande Prairie .......... 5 Figure 3: 5-Year Rainfall Event (Gumbel Distribution) – 9 Stations + City of Grande Prairie IDF Curve...............................................................................................13 Figure 4: 100-Year Rainfall Event (Gumbel Distribution) – 9 Stations + City of Grande Prairie IDF Curve...............................................................................................14 Figure 5: 5-Year Rainfall Event (Gumbel Distribution) – 9 Stations + All Station Combined including 95% Confidence Interval ...................................................15 Figure 6: 100-Year Rainfall Event (Gumbel Distribution) – 9 Stations + All Station Combined including 95% Confidence Interval ...................................................16 Figure 7: New City of Grande Prairie IDF Curves (Based on Upper 95% Confidence Interval of All 9 Stations) – Dots are Gumbel Distribution Data Points; Lines are IDF Curves Derived from Equation ..............................................................17 Figure 8: New City of Grande Prairie IDF Curves (Based on Upper 95% Confidence Interval of All 9 Stations) vs. Current City of Grande Prairie IDF curves ............20 Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure 9: Proposed New City of Grande Prairie IDF Curves (Based on Upper 95% Confidence Interval of All 9 Stations) vs. Current City of Edmonton IDF curves ...............................................................................................................21 Figure 10: Current City of Grande Prairie 4-Hour Chicago Distribution Design Rainfalls ......26 Figure 11: New City of Grande Prairie 4-Hour Chicago Distribution Design Rainfalls (discretized at 5 minutes interval) ......................................................................27 Figure 12: New City of Grande Prairie 24-Hour Chicago Distribution Design Rainfalls (discretized at 15 minutes interval) ....................................................................28 Figure 13: New City of Grande Prairie 4-Hour Chicago Distribution Design Rainfalls vs. Current for the 5-year (left) and 100-year (right) Events ....................................28 Figure 14: Current 100-Year City of Grande Prairie 12-Hour AES Design Rainfall...............35 Figure 15: New 100-Year City of Grande Prairie 12-Hour AES Distribution Design Rainfall vs. Current ............................................................................................36 Figure 16: 24-hour SCS Type II Distribution ........................................................................37 Figure 17: Current 100-Year City of Grande Prairie 24-Hour SCS Type II Design Rainfall...39 Figure 18: New City of Grande Prairie 24-Hour SCS Type II Distribution Design Rainfalls ..40 Figure 19: New City of Grande Prairie 24-Hour SCS Type II Distribution Design Rainfalls vs. Current for the 100-Year Event ....................................................................40 Figure 20: 24-hour Huff Distribution and SCS Type II Distribution â&#x20AC;&#x201C; Cumulative Rainfall Depth ................................................................................................................45 Figure 21: 24-hour Huff Distribution and SCS Type II Distribution â&#x20AC;&#x201C; Fraction of Rainfall Depth by 15 minutes Time Step ........................................................................45 Figure 22: New City of Grande Prairie 12-Hour Huff Distribution (1st quartile) Design Rainfalls ............................................................................................................48 Figure 23: New City of Grande Prairie 12-Hour Huff Distribution (2nd quartile) Design Rainfalls ............................................................................................................48 Figure 24: New City of Grande Prairie 24-Hour Huff Distribution (1st quartile) Design Rainfalls ............................................................................................................49 Figure 25: New City of Grande Prairie 24-Hour Huff Distribution (2nd quartile) Design Rainfalls ............................................................................................................49 Figure 26: Comparison of New City of Grande Prairie 12-Hour Distributions .......................50 Figure 27: Comparison of New City of Grande Prairie 24-Hour Distributions .......................50

List of Tables Table 1: Selected Rainfall Gauges for Further Evaluation ..................................................... 6 Table 2: Yearly Peak Rainfall Intensity ................................................................................. 7

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 3: Comparison of Gumbel Distribution Results for Select Stations and Select Durations ...........................................................................................................14 Table 4: New City of Grande Prairie IDF Curves â&#x20AC;&#x201C; Equation and Parameters......................17 Table 5: New City of Grande Prairie IDF Curves â&#x20AC;&#x201C; Average Rainfall Intensity......................18 Table 6: New City of Grande Prairie 4-Hour Chicago Distribution Design Rainfall, in mm/hr ................................................................................................................29 Table 7: New City of Grande Prairie 24-Hour Chicago Distribution Design Rainfall, in mm/hr ................................................................................................................31 Table 8: New City of Grande Prairie 12-Hour AES Distribution Design Rainfall, in mm/hr....36 Table 9: New City of Grande Prairie 24-Hour SCS Type II Design Storm, in mm/hr.............41 Table 10: New City of Grande Prairie 12-Hour Huff (1st quartile) Design Storm, in mm/hr ....51 Table 11: New City of Grande Prairie 12-Hour Huff (2nd quartile) Design Storm, in mm/hr ...53 Table 12: New City of Grande Prairie 24-Hour Huff (1st quartile) Design Storm, in mm/hr ....55 Table 13: New City of Grande Prairie 24-Hour Huff (2nd quartile) Design Storm, in mm/hr ...58

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

1.0 Design Rainfall Assessment Background Following a very intense rainfall on August 2, 2016, recorded to exceed a 1:100-year 1-hour event (based on the Cityâ&#x20AC;&#x2122;s current IDF curves) at two of the City rainfall gauges, it was decided to review whether the current IDF curves and design rainfalls used to design the Cityâ&#x20AC;&#x2122;s drainage system are adequate. The current City of Grande Prairie IDF (Intensity-Frequency-Duration) curves, shown in Figure 1, were derived from the IDF curves developed by Environment Canada for the Grande Prairie Regional Airport. These curves used rainfall data collected between 1968 and 1993. There is a significant discontinuity in the rainfall intensity at the 2 hours duration by about 10 to 20%; this is because two equations were developed for each return period. Consequently, the intensity of the 100-year event at 1.99 hours is similar to the intensity of the 25-year event at 2.01 hours.

Current IDF 100-yr Current IDF 50-yr Current IDF 25-yr Current IDF 10-yr Current IDF 5-yr Current IDF 2-yr

Rainfall Intensity (mm/hr)

100

1 1

100

Rainfall Duration (minutes)

Figure 1: Current City of Grande Prairie IDF curves

Sameng Inc.

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Review of IDF Curves 1.2.1

Rainfall Data Collection and Compilation

Data from nine government rainfall gauges in vicinity of the City of Grande Prairie was collected and reviewed. These stations are illustrated in Figure 2 and summarized in Table 1. These gauges were selected for their proximity to the City of Grande Prairie (within 100 km), as well as their similar surrounding topography and land usage (generally flat with mostly agricultural development).

Figure 2: Location of Selected Rainfall Gauges in Proximity of City of Grande Prairie

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 1: Selected Rainfall Gauges for Further Evaluation

Coordinate

Distance from Grande Prairie (100 Avenue and 100 Street)

Years Available

Grande Prairie A (AB 3072920) 1

Lat: 55.18 Long: -118.8847

5.8 km (west)

1968 – 1993 (26 years)

Teepee Creek - AARD (07GJ803) 2

Lat: 55.3524 Long: -118.4076

31.9 km (northwest)

2007 – 2017 (11 years)

Beaverlodge CDA (AB 3070560) 1

Lat: 55.1966 Long: -119.3964

38.4 km (west)

1961 – 1994 (34 years)

Beaverlodge - MSC (MSC-003) 2

Lat: 55.1966 Long: -119.3964

38.4 km (west)

2005 – 2017 (13 years)

La Glace – AARD (07GE804) 2

Lat: 55.4219 Long: -119.2547

40.4 km (northwest)

2007 – 2017 (11 years)

Peoria – AARD (07GJ802) 2

Lat: 55.6212 Long: -118.293

59.4 km (northeast)

2002 – 2017 (16 years)

Rycroft – AGCM (07DF808) 2

Lat: 55.7768 Long: -118.6681

68.1 km (north)

2007 – 2017 (11 years)

Eaglesham – AARD (07FD806) 2

Lat: 55.8081 Long: -117.8866

91.3 km (northeast)

2007 – 2017 (11 years)

Watino (AB 3077246) 1

Lat: 55.72 Long: -117.63

95.8 km (northeast)

1963 – 1993 (31 years)

Station Name

Notes: 1. Rainfall data downloaded from http://climate.weather.gc.ca/prods_servs/engineering_e.html. 2. Rainfall data downloaded from https://rivers.alberta.ca/.

Rainfall data for three of these stations (in yellow: Grande Prairie A, Beaverlodge CDA and Watino) was collected and post-processed by Environment Canada (EC) from the 1960s until 1993-94. For these stations, yearly peak rainfall intensity data was tabulated by EC for various duration (5-10-15-30 minutes, 1-2-6-12-24 hours). This information was quality controlled by EC and is considered accurate. Rainfall data at ‘Grande Prairie A’ is still being collected by NAV CANADA but is only tabulated every six hours; it was decided not to collect/purchase this data. We are unaware of the status of the other two gauges. Rainfall data for the other six stations (in red) has been collected by Alberta Agriculture and Forestry (AAF) since the 2000s; they are all still operational. Data for these stations was tabulated every 15 minutes by AAF, but it is not quality controlled. For each station and for each duration (15-30 minutes, 1-2-6-12-24 hours), the yearly peak rainfall intensity was tabulated. For quality control purposes, all tabulated peak values were compared to historical weather radar maps (http://climate.weather.gc.ca/radar/index_e.html) to confirm that these rainfalls actually happened; some of the peak values were revised in the process. The yearly peak rainfall intensity data for all nine gauges is tabulated in Table 2.

Sameng Inc.

The City of Grande Prairie - Storm Drainage Master Plan Table 2: Yearly Peak Rainfall Intensity Stations - Color-coded Peoria – AARD Teepee Creek - AARD Grande Prairie A 5 minutes Peak Rainfall Year Intensity (mm/hr) 1968 51.6 1969 69.6 1970 24.0 1971 67.2 1972 73.2 1974 36.0 1975 21.6 1976 33.6 1977 100.8 1978 34.8 1979 34.8 1980 38.4 1982 63.6 1984 48.0 1985 86.4 1986 57.6 1987 57.6 1988 28.8 1989 85.2 1991 96.0 1992 84.0 1993 52.8 1961 49.2 1962 73.2 1963 109.2

10 minutes Peak Rainfall Year Intensity (mm/hr) 1968 47.4 1969 44.4 1970 21.6 1971 62.4 1972 58.2 1974 31.8 1975 12.0 1976 31.8 1977 70.2 1978 24.6 1979 29.4 1980 33.0 1982 51.6 1984 27.6 1985 67.2 1986 34.2 1987 32.4 1988 21.6 1989 60.0 1991 63.6 1992 58.8 1993 39.6 1961 36.6 1962 67.2 1963 62.4

15 minutes Peak Rainfall Year Intensity (mm/hr) 2003 43.2 2004 40.4 2005 43.6 2006 20.0 2007 79.6 2008 82.4 2009 9.2 2010 25.6 2011 23.2 2012 33.2 2013 79.6 2014 34.8 2015 19.6 2016 28.0 2017 37.6 2008 45.6 2009 22.8 2010 15.2 2011 33.6 2012 22.4 2013 35.2 2014 35.6 2015 47.2 2016 24.4 2017 26.0

30 minutes Peak Rainfall Year Intensity (mm/hr) 2003 24.6 2004 22.0 2005 29.0 2006 15.2 2007 43.4 2008 52.0 2009 7.4 2010 15.4 2011 17.6 2012 20.2 2013 56.2 2014 17.4 2015 16.8 2016 27.4 2017 26.4 2008 43.0 2009 14.0 2010 8.4 2011 21.4 2012 20.0 2013 27.4 2014 21.2 2015 30.0 2016 20.8 2017 19.4

La Glace – AARD Rycroft – AGCM Eaglesham – AARD

1 hour Year 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 2009 2010 2011 2012 2013 2014 2015 2016

Peak Rainfall Intensity (mm/hr) 4.6 12.6 16.4 14.7 8.0 24.0 28.4 6.5 9.3 11.3 12.7 36.9 9.6 10.5 15.2 17.4 22.8 9.6 5.6 14.8 11.4 17.2 10.8 18.7 13.6

Page 1 of 6

2 hours Year 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 2009 2010 2011 2012 2013 2014 2015 2016

Peak Rainfall Intensity (mm/hr) 4.1 7.6 13.4 8.1 5.4 12.1 16.2 5.4 5.6 8.2 7.1 20.6 6.4 7.0 11.3 11.6 11.4 5.2 5.3 10.2 6.8 8.7 6.1 9.9 6.9

Beaverlodge - MSC Beaverlodge CDA Watino 6 hours Year 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 2009 2010 2011 2012 2013 2014 2015 2016

Peak Rainfall Intensity (mm/hr) 2.5 2.7 4.6 3.9 3.8 4.1 5.4 2.1 5.2 4.8 3.5 7.2 4.1 3.4 4.1 3.9 3.8 2.3 4.0 5.1 3.1 2.9 2.4 3.4 4.2

12 hours Peak Rainfall Year Intensity (mm/hr) 2002 1.8 2003 1.4 2004 2.4 2005 2.1 2006 2.3 2007 2.6 2008 2.7 2009 1.1 2010 4.3 2011 4.4 2012 2.3 2013 3.9 2014 2.3 2015 2.1 2016 2.2 2017 3.1 2008 1.9 2009 1.4 2010 3.0 2011 4.1 2012 2.2 2013 1.5 2014 1.7 2015 2.6 2016 3.2

24 hours Peak Rainfall Year Intensity (mm/hr) 2002 1.1 2003 0.7 2004 2.0 2005 1.1 2006 1.3 2007 1.6 2008 1.4 2009 0.7 2010 2.5 2011 3.1 2012 1.7 2013 1.9 2014 1.3 2015 1.1 2016 1.9 2017 2.1 2008 1.0 2009 0.9 2010 1.7 2011 2.7 2012 1.6 2013 0.9 2014 1.0 2015 1.4 2016 2.4

The City of Grande Prairie - Storm Drainage Master Plan Table 2: Yearly Peak Rainfall Intensity Stations - Color-coded Peoria – AARD Teepee Creek - AARD Grande Prairie A 5 minutes Peak Rainfall Year Intensity (mm/hr) 1964 103.2 1965 188.4 1966 88.8 1967 18.0 1968 21.6 1969 15.6 1970 100.8 1971 79.2 1972 43.2 1974 43.2 1975 27.6 1976 67.2 1977 85.2 1978 48.0 1979 50.4 1980 55.2 1981 39.6 1982 18.0 1984 52.8 1985 24.0 1986 99.6 1987 84.0 1988 37.2 1989 90.0 1990 28.8

10 minutes Peak Rainfall Year Intensity (mm/hr) 1964 90.0 1966 67.2 1967 18.0 1968 13.8 1969 12.0 1970 99.0 1971 62.4 1972 37.8 1974 24.6 1975 19.8 1976 48.6 1977 71.4 1978 26.4 1979 49.8 1980 42.0 1981 33.6 1982 15.6 1984 31.2 1985 16.2 1986 77.4 1987 50.4 1988 31.8 1989 58.8 1990 28.8 1991 39.6

15 minutes Peak Rainfall Year Intensity (mm/hr) 1968 33.6 1969 34.4 1970 16.4 1971 45.6 1972 54.8 1974 28.4 1975 10.0 1976 21.2 1977 48.8 1978 22.0 1979 21.2 1980 29.2 1982 39.2 1984 24.8 1985 59.2 1986 26.0 1987 29.6 1988 21.2 1989 48.0 1991 44.8 1992 52.4 1993 35.2 2008 22.4 2009 52.4 2010 86.4

30 minutes Peak Rainfall Year Intensity (mm/hr) 1968 23.4 1969 18.2 1970 8.6 1971 23.8 1972 32.6 1974 14.2 1975 6.6 1976 12.6 1977 24.8 1978 17.0 1979 15.0 1980 22.2 1981 17.6 1982 25.2 1984 15.4 1985 37.6 1986 18.2 1987 25.8 1988 15.8 1989 37.4 1991 24.8 1992 27.6 1993 23.4 2008 14.0 2009 35.0

La Glace – AARD Rycroft – AGCM Eaglesham – AARD

1 hour Year 2017 1968 1969 1970 1971 1972 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1991 1992 1993

Peak Rainfall Intensity (mm/hr) 11.3 12.2 10.2 4.8 14.5 18.3 9.1 5.3 10.2 12.4 9.6 8.8 11.7 15.3 17.5 12.0 8.1 20.7 11.1 14.8 12.7 21.8 14.8 14.0 20.9

Page 2 of 6

2 hours Year 2017 1968 1969 1970 1971 1972 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1991 1992 1993

Peak Rainfall Intensity (mm/hr) 7.6 7.6 6.0 4.6 8.2 9.9 6.9 4.2 7.5 6.2 5.6 4.4 6.8 8.0 12.2 6.0 5.9 10.4 6.9 9.3 9.9 16.4 9.5 7.3 12.8

Beaverlodge - MSC Beaverlodge CDA Watino 6 hours Year 2017 1968 1969 1970 1971 1972 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992

Peak Rainfall Intensity (mm/hr) 4.3 4.3 3.6 3.1 4.2 3.7 3.5 2.1 4.7 2.8 3.1 3.4 4.1 2.7 9.5 3.9 4.1 3.7 3.9 4.7 6.0 9.1 3.7 4.9 2.6

12 hours Peak Rainfall Year Intensity (mm/hr) 2017 2.8 1968 3.5 1969 3.0 1970 1.6 1971 2.5 1972 1.8 1974 1.8 1975 1.7 1976 3.7 1977 2.2 1978 1.9 1979 2.3 1980 2.2 1981 1.4 1982 5.4 1983 2.8 1984 2.9 1985 2.1 1986 2.5 1987 2.5 1988 3.5 1989 6.0 1990 2.9 1991 3.0 1992 1.4

24 hours Peak Rainfall Year Intensity (mm/hr) 2017 1.9 1968 3.0 1969 2.3 1970 0.8 1971 1.8 1972 0.9 1974 0.9 1975 1.4 1976 2.1 1977 2.0 1978 1.0 1979 1.3 1980 1.1 1981 1.0 1982 3.6 1983 2.2 1984 2.2 1985 1.4 1986 1.3 1987 1.5 1988 2.0 1989 3.7 1990 2.5 1991 1.7 1992 0.7

The City of Grande Prairie - Storm Drainage Master Plan Table 2: Yearly Peak Rainfall Intensity Stations - Color-coded Peoria – AARD Teepee Creek - AARD Grande Prairie A 5 minutes Peak Rainfall Year Intensity (mm/hr) 1991 50.4 1992 51.6 1993 122.4 1994 62.4 1963 63.6 1964 88.8 1967 43.2 1968 103.2 1969 30.0 1972 36.0 1977 207.6 1978 122.4 1979 48.0 1981 57.6 1982 67.2 1984 92.4 1985 37.2 1986 68.4 1987 97.2 1988 16.8 1989 60.0 1990 20.4 1991 55.2 1992 98.4 1993 92.4

10 minutes Peak Rainfall Year Intensity (mm/hr) 1992 43.2 1993 70.8 1994 36.0 1963 39.6 1964 47.4 1967 37.8 1968 68.4 1969 24.6 1972 31.8 1977 103.8 1978 61.2 1979 33.6 1981 48.0 1982 39.0 1984 73.8 1985 28.2 1986 55.8 1987 92.4 1988 13.8 1989 46.8 1990 15.6 1991 28.8 1992 54.0 1993 48.6

15 minutes Peak Rainfall Year Intensity (mm/hr) 2011 27.2 2012 21.2 2013 20.4 2014 88.8 2015 35.6 2016 37.2 2017 17.6 2008 12.8 2009 27.2 2010 13.6 2011 32.4 2012 31.2 2013 34.0 2014 23.2 2015 38.4 2016 40.4 2017 43.6 2008 63.6 2009 36.8 2010 34.8 2011 24.8 2012 79.6 2013 29.2 2014 18.8 2015 28.0

30 minutes Peak Rainfall Year Intensity (mm/hr) 2010 47.2 2011 21.8 2012 13.6 2013 14.6 2014 62.8 2015 27.2 2016 25.0 2017 11.8 2008 9.8 2009 14.2 2010 7.8 2011 25.0 2012 17.6 2013 33.0 2014 20.2 2015 36.2 2016 32.6 2017 22.0 2008 39.8 2009 18.4 2010 21.6 2011 16.8 2012 42.4 2013 28.2 2014 13.6

La Glace – AARD Rycroft – AGCM Eaglesham – AARD

1 hour Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 2009 2010 2011 2012

Peak Rainfall Intensity (mm/hr) 7.6 19.7 24.4 16.4 9.3 9.6 34.5 15.2 13.5 9.1 6.4 9.6 4.7 15.0 14.0 25.0 12.6 22.7 21.1 13.8 20.2 9.2 11.6 13.1 21.3

Page 3 of 6

2 hours Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 2009 2010 2011 2012

Peak Rainfall Intensity (mm/hr) 5.6 11.8 12.2 10.2 5.5 6.2 17.5 8.9 7.8 7.2 4.5 7.8 4.1 9.1 11.1 14.9 9.5 13.5 10.8 6.9 10.3 4.7 5.9 8.7 10.7

Beaverlodge - MSC Beaverlodge CDA Watino 6 hours Year 1993 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 2009 2010 2011

Peak Rainfall Intensity (mm/hr) 4.3 2.0 4.6 4.1 3.5 3.1 3.5 5.9 4.8 4.4 5.0 2.4 2.8 3.3 4.3 5.7 6.6 5.2 5.5 4.5 2.7 3.5 2.0 3.3 5.1

12 hours Peak Rainfall Year Intensity (mm/hr) 1993 2.2 2008 1.1 2009 2.6 2010 2.1 2011 2.9 2012 2.0 2013 2.1 2014 2.9 2015 3.0 2016 2.3 2017 2.9 2008 1.7 2009 1.5 2010 3.1 2011 4.0 2012 3.9 2013 4.1 2014 3.1 2015 2.7 2016 2.3 2017 2.1 2008 2.2 2009 1.0 2010 2.9 2011 4.3

24 hours Peak Rainfall Year Intensity (mm/hr) 1993 1.6 2008 0.8 2009 1.6 2010 1.4 2011 2.0 2012 1.6 2013 1.2 2014 1.5 2015 1.8 2016 2.2 2017 1.5 2008 1.1 2009 1.0 2010 2.1 2011 3.0 2012 2.6 2013 2.4 2014 2.3 2015 1.6 2016 1.5 2017 1.4 2008 1.1 2009 0.6 2010 1.8 2011 2.7

10 minutes Peak Rainfall Year Intensity (mm/hr)

15 minutes Peak Rainfall Year Intensity (mm/hr) 2016 62.0 2017 41.6 2006 19.2 2007 24.0 2008 19.2 2009 25.2 2010 18.4 2011 13.2 2012 20.4 2013 94.0 2014 16.0 2015 30.4 2016 30.4 2017 12.8 1961 30.4 1962 52.8 1963 45.6 1964 74.0 1966 49.6 1967 18.4 1968 13.2 1969 12.0 1970 87.2 1971 42.8 1972 35.6

30 minutes Peak Rainfall Year Intensity (mm/hr) 2015 15.0 2016 45.6 2017 41.4 2006 9.8 2007 16.6 2008 10.8 2009 14.6 2010 11.4 2011 7.6 2012 10.3 2013 50.8 2014 9.2 2015 26.4 2016 30.2 2017 12.2 1961 21.4 1962 29.0 1963 23.4 1964 38.6 1966 27.4 1967 10.6 1968 9.6 1969 8.2 1970 46.8 1971 26.4

La Glace – AARD Rycroft – AGCM Eaglesham – AARD

1 hour Year 2013 2014 2015 2016 2017 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 1961 1962 1963 1964 1966 1967 1968 1969

Peak Rainfall Intensity (mm/hr) 20.1 8.6 7.5 26.5 21.4 7.0 11.4 6.0 13.5 7.5 5.6 10.1 26.7 7.7 17.1 16.9 10.7 12.4 14.5 11.7 20.3 21.6 6.6 7.6 5.8

Page 4 of 6

2 hours Year 2013 2014 2015 2016 2017 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 1961 1962 1964 1966 1967 1968 1969 1970

Peak Rainfall Intensity (mm/hr) 14.0 4.5 6.2 13.4 10.7 4.6 6.2 3.6 7.9 4.4 4.5 6.6 13.3 7.4 10.3 8.4 8.4 7.1 7.5 10.3 11.6 4.5 7.0 4.3 13.0

Beaverlodge - MSC Beaverlodge CDA Watino 6 hours Year 2012 2013 2014 2015 2016 2017 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 1961 1962 1964 1966 1967 1968 1969

Peak Rainfall Intensity (mm/hr) 3.6 5.2 2.6 4.9 4.5 3.9 2.7 2.5 1.9 4.2 3.1 3.7 2.3 4.6 3.8 5.3 3.6 5.4 3.1 4.5 6.4 4.7 2.2 3.9 2.8

12 hours Peak Rainfall Year Intensity (mm/hr) 2012 2.3 2013 3.3 2014 1.8 2015 2.8 2016 3.0 2017 2.0 2006 1.4 2007 1.4 2008 1.0 2009 3.2 2010 2.4 2011 3.0 2012 1.4 2013 2.3 2014 2.2 2015 4.2 2016 2.2 2017 4.3 1961 2.1 1962 2.6 1964 5.0 1966 2.9 1967 1.1 1968 3.1 1969 2.4

24 hours Peak Rainfall Year Intensity (mm/hr) 2012 1.4 2013 1.7 2014 1.3 2015 1.4 2016 2.0 2017 1.2 2006 1.0 2007 0.8 2008 0.8 2009 1.9 2010 1.8 2011 2.1 2012 1.1 2013 1.6 2014 1.3 2015 2.7 2016 1.6 2017 2.7 1961 1.2 1962 1.5 1964 4.5 1966 2.4 1967 0.6 1968 2.4 1969 1.9

10 minutes Peak Rainfall Year Intensity (mm/hr)

15 minutes Peak Rainfall Year Intensity (mm/hr) 1974 18.4 1975 17.2 1976 41.6 1977 52.0 1978 20.8 1979 37.2 1980 30.4 1981 30.0 1982 15.6 1984 23.2 1985 16.0 1986 52.4 1987 35.6 1988 33.2 1989 42.8 1990 24.8 1991 28.8 1992 41.2 1993 55.2 1994 26.4 1963 33.6 1964 42.8 1967 26.4 1968 56.8 1969 18.4

30 minutes Peak Rainfall Year Intensity (mm/hr) 1972 32.6 1974 13.8 1975 11.2 1976 31.4 1977 29.0 1978 15.8 1979 26.6 1980 15.2 1981 20.4 1982 12.0 1984 23.2 1985 9.2 1986 27.0 1987 21.0 1988 21.2 1989 23.2 1990 14.2 1991 16.6 1992 29.2 1993 29.4 1994 17.6 1963 24.4 1964 36.6 1967 22.4 1968 48.8

La Glace – AARD Rycroft – AGCM Eaglesham – AARD

1 hour Year 1970 1971 1972 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1963

Peak Rainfall Intensity (mm/hr) 25.9 17.5 17.5 9.9 6.1 17.3 15.7 9.1 17.8 9.7 10.9 9.7 12.5 18.8 8.0 13.7 11.5 12.3 12.5 8.1 10.0 19.8 14.7 12.8 16.0

Page 5 of 6

2 hours Year 1971 1972 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1963 1964

Peak Rainfall Intensity (mm/hr) 12.0 10.7 6.0 4.3 10.7 8.4 5.9 9.9 5.7 5.5 7.5 7.1 10.4 5.2 12.9 8.9 6.3 8.2 7.0 5.7 10.6 7.5 7.2 8.4 10.6

Beaverlodge - MSC Beaverlodge CDA Watino 6 hours Year 1970 1971 1972 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1994 1963 1964

Peak Rainfall Intensity (mm/hr) 4.3 6.1 4.5 2.9 2.2 3.7 4.4 3.7 4.6 3.2 2.0 4.6 3.5 4.2 3.2 5.4 6.5 4.8 3.4 6.0 2.7 3.6 3.0 3.4 5.6

12 hours Peak Rainfall Year Intensity (mm/hr) 1970 2.2 1971 3.3 1972 2.2 1974 1.5 1975 2.0 1976 2.4 1977 2.7 1978 2.6 1979 2.5 1980 2.1 1981 1.7 1982 4.3 1983 2.3 1984 2.3 1985 2.0 1986 3.2 1987 4.1 1988 2.6 1989 2.6 1990 5.5 1991 2.1 1992 2.2 1994 2.0 1963 1.8 1964 5.0

24 hours Peak Rainfall Year Intensity (mm/hr) 1970 1.1 1971 1.8 1972 1.2 1974 0.7 1975 1.5 1976 1.7 1977 1.6 1978 1.3 1979 1.8 1980 1.4 1981 1.3 1982 3.9 1983 1.7 1984 1.7 1985 1.5 1986 2.1 1987 2.2 1988 1.5 1989 1.4 1990 4.8 1991 1.3 1992 1.3 1993 1.4 1994 1.7 1963 1.8

10 minutes Peak Rainfall Year Intensity (mm/hr)

15 minutes Peak Rainfall Year Intensity (mm/hr) 1972 30.4 1977 72.0 1978 40.8 1979 25.6 1981 43.6 1982 28.0 1984 63.2 1985 25.2 1986 55.6 1987 75.2 1988 13.6 1989 44.4 1990 13.6 1991 20.8 1992 36.0 1993 33.2

30 minutes Peak Rainfall Year Intensity (mm/hr) 1969 11.2 1972 20.4 1977 36.0 1978 21.0 1979 18.6 1981 35.8 1982 14.0 1984 60.6 1985 18.4 1986 39.6 1987 38.4 1988 11.2 1989 30.6 1990 8.4 1991 18.4 1992 18.0 1993 19.6

La Glace – AARD Rycroft – AGCM Eaglesham – AARD

1 hour Year 1964 1967 1968 1969 1972 1977 1978 1979 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993

Peak Rainfall Intensity (mm/hr) 18.8 14.5 38.9 7.6 10.2 18.0 13.7 10.4 21.2 7.0 14.0 37.0 12.1 21.7 19.3 11.2 17.0 6.2 14.9 9.0 11.4

Page 6 of 6

2 hours Year 1967 1968 1969 1972 1977 1978 1979 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993

Peak Rainfall Intensity (mm/hr) 7.6 23.6 6.6 5.4 9.0 7.2 5.5 11.3 6.3 10.2 21.5 6.3 11.4 12.3 11.2 9.3 4.2 11.9 4.9 7.2

Beaverlodge - MSC Beaverlodge CDA Watino 6 hours Year 1967 1968 1969 1972 1977 1978 1979 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1993

Peak Rainfall Intensity (mm/hr) 2.5 8.6 3.0 3.1 4.8 3.4 3.1 4.3 4.7 3.5 7.3 3.8 3.8 4.2 5.8 3.2 1.8 5.3 3.9

12 hours Peak Rainfall Year Intensity (mm/hr) 1967 1.3 1968 4.3 1969 1.9 1972 1.5 1977 4.2 1978 1.7 1979 2.8 1981 2.1 1982 2.5 1983 1.7 1984 3.8 1985 2.7 1986 1.9 1987 2.1 1988 2.9 1989 2.4 1990 1.2 1991 2.7

24 hours Peak Rainfall Year Intensity (mm/hr) 1964 2.8 1967 0.7 1968 3.9 1969 1.6 1972 0.8 1977 2.1 1978 1.0 1979 1.5 1981 1.8 1982 1.5 1983 0.9 1984 2.7 1985 1.4 1986 0.9 1987 1.4 1988 2.0 1989 1.5 1990 0.7 1991 1.6 1992 0.9 1993 1.8

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.2.2

City of Grande Prairie

Frequency Analysis – Select Stations

For each station, a frequency analysis was completed for select durations (i.e. 5-10-15-30 minutes, 1-2-6-12-24 hours). The Gumbel distribution, one of the most widely used distributions for frequency analysis of maximum rainfall, was used to estimate the rainfall intensity associated with various return periods. The data from all stations fit the Gumbel distribution quite well. Results for each station are shown in Appendix A (Figure A-1 to Figure A-9). Figure 3 shows the Gumbel distribution of all stations for the 5-year event; Figure 4 shows it for the 100-year event. Table 3 compares the results for a select number of durations and return periods. Some relevant observations are: • The curves for all stations are generally within the same intensity range and follow a similar shape. All curves intertwine, and none stand out as being flawed or significantly different. For example, the La Glace station has the highest short duration intensity, but also has the smallest long duration intensity, while the Grande Prairie A station is the opposite. • For the first 2 hours duration and for all return periods, the City of Grande Prairie IDF curves’ rainfall intensity are generally low, but not unreasonable. Beyond the 2 hours mark, the City’s IDF curves are actually on the high end of the curves.

Beaverlodge CDA Beaverlodge - MSC Eaglesham AARD Grande Prairie A La Glace AARD Peoria AARD Rycroft AGCM Teepee Creek AARD Watino CGP IDF Curve

Rainfall Intensity (mm/hr)

100

1 1

100

1000

Rainfall Duration (minutes)

Figure 3: 5-Year Rainfall Event (Gumbel Distribution) – 9 Stations + City of Grande Prairie IDF Curve

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie Beaverlodge CDA Beaverlodge - MSC Eaglesham AARD Grande Prairie A La Glace AARD Peoria AARD Rycroft AGCM Teepee Creek AARD Watino CGP IDF Curve

Rainfall Intensity (mm/hr)

100

1 1

100

1000

Rainfall Duration (minutes)

Figure 4: 100-Year Rainfall Event (Gumbel Distribution) – 9 Stations + City of Grande Prairie IDF Curve Table 3: Comparison of Gumbel Distribution Results for Select Stations and Select Durations Duration 30 minutes

2 hours

24 hours

Rainfall Intensity (mm/hr) 5-year

100-year

Range: 26.6 – 39.3 Avg: 32.2 CGP IDF: 28.0 (low) Range: 9.1 – 13.1 Avg: 11.0 CGP IDF: 10.2 / 12.0 (avg) Range: 1.8 – 2.5 Avg: 2.1 CGP IDF: 2.3 (mid-high)

Range: 46.5 – 79.8 Avg: 60.6 CGP IDF: 48.3 (low) Range: 14.5 – 24.8 Avg: 19.2 CGP IDF: 17.2 / 21.1 (avg) Range: 2.8 – 4.8 Avg: 3.8 CGP IDF: 4.3 (mid-high)

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.2.3

City of Grande Prairie

Frequency Analysis â&#x20AC;&#x201C; All Stations Combined

Since the curves from all stations are similar, and their average yearly precipitation volume is in the same range (6 AAF stations individual average: from 353mm to 431mm, average of all 6 stations: 382mm), rainfall data from all 9 stations were combined to create a single curve. Figure 5 shows the Gumbel distribution curve for the 5-year event; Figure 6 shows it for the 100-year event. Full results are in Appendix A (Figure A-10 and A-11). Combining data from all 9 stations significantly increased the number of data points used to develop the curves (up to 146 years of data), which narrowed the confidence interval. For example, when using only 10 years of data, the confidence interval would range between 15% (2-year) and 50% (100-year) of the average which is quite large; when using 146 years of data, the confidence interval reduced to between 5% (2-year) and 15% (100-yr).

Beaverlodge CDA Beaverlodge - MSC Eaglesham AARD Grande Prairie A La Glace AARD Peoria AARD Rycroft AGCM Teepee Creek AARD Watino All 9 Stations All 9 Stations (95% C.I.)

Rainfall Intensity (mm/hr)

100

1 1

100

1000

Rainfall Duration (minutes)

Figure 5: 5-Year Rainfall Event (Gumbel Distribution) â&#x20AC;&#x201C; 9 Stations + All Station Combined including 95% Confidence Interval

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie Beaverlodge CDA Beaverlodge - MSC Eaglesham AARD Grande Prairie A La Glace AARD Peoria AARD Rycroft AGCM Teepee Creek AARD Watino All 9 Stations All 9 Stations (95% C.I.)

Rainfall Intensity (mm/hr)

100

1 1

100

1000

Rainfall Duration (minutes)

Figure 6: 100-Year Rainfall Event (Gumbel Distribution) â&#x20AC;&#x201C; 9 Stations + All Station Combined including 95% Confidence Interval 1.2.4

Development of New City of Grande Prairie IDF Curves

The upper 95% confidence interval of the curve using data from all 9 stations was used to develop the new City of Grande Prairie IDF curves. This is because it largely corresponds to the upper envelope of the 9 individual station curves, thus offering a factor of safety. Using the average curve would result in a greater probability of underestimating the rainfall intensity. The developed IDF curves are shown in Figure 7. Single IDF curve equations were used for simplification purposes. The equations are presented in Table 4; the tabulated results are presented in Table 5. The new IDF curves match the Gumbel distribution data points very well for durations less or equal to 1 hour (within 5%). However, they cannot match all data points for the higher duration (up to 20% difference), as the IDF curve equation does not allow the longer duration section of the curves to curve back up (when plotted on log-log chart). The IDF curves were best fitted as to not grossly underestimate the average intensity for rainfalls of longer duration, especially the 24-hour event.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Rainfall Intensity (mm/hr)

100

10 New IDF 1000-yr New IDF 100-yr New IDF 50-yr New IDF 25-yr New IDF 10-yr New IDF 5-yr New IDF 2-yr 1 1

100

1000

Rainfall Duration (minutes)

Figure 7: New City of Grande Prairie IDF Curves (Based on Upper 95% Confidence Interval of All 9 Stations) – Dots are Gumbel Distribution Data Points; Lines are IDF Curves Derived from Equation Table 4: New City of Grande Prairie IDF Curves – Equation and Parameters Return Period 2 year 5 year 10 year 25 year 50 year 100 year 1000 year **

Average Intensity (mm/hr) 271.3 (t + 2.35) -0.713 393.6 (t + 1.64) -0.714 477.6 (t + 1.38) -0.714 585.1 (t + 1.18) -0.715 672.3 (t + 1.12) -0.718 753.0 (t + 1.04) -0.718 1030.8 (t + 0.92) -0.722

Note: t is in minutes ** Use with discretion

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 5: New City of Grande Prairie IDF Curves â&#x20AC;&#x201C; Average Rainfall Intensity Minutes

Hours

5 6 7 8 9 10 11 12 13 14 15 16

0.25

17 18 19 20 21 22 23 24 25 26 27 28 29 30 35 40 45 50

0.50

0.75

55 60 75 90 105 120 150

1.00 1.25 1.50 1.75 2.00 2.50

180 210 240

3.00 3.50 4.00

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

1000-yr **

65.4 59.7 55.1 51.3 48.0 45.2 42.8 40.6 38.7 37.0 35.5 34.1 32.8 31.7 30.6 29.6 28.7 27.9 27.1 26.3 25.6 25.0 24.4 23.8 23.3 22.7 20.5 18.8 17.3 16.1 15.1 14.2 12.2 10.8 9.7 8.8 7.5 6.6 5.9 5.4

101.9 92.2 84.4 78.1 72.7 68.2 64.3 60.9 57.9 55.3 52.9 50.7 48.7 47.0 45.3 43.8 42.4 41.1 39.9 38.8 37.8 36.8 35.9 35.0 34.2 33.4 30.1 27.5 25.3 23.5 22.0 20.8 17.8 15.6 14.0 12.8 10.9 9.6 8.6 7.8

127.2 114.6 104.7 96.6 89.8 84.1 79.2 75.0 71.2 67.9 64.9 62.2 59.7 57.5 55.5 53.6 51.9 50.3 48.8 47.5 46.2 45.0 43.8 42.7 41.7 40.8 36.7 33.5 30.9 28.7 26.8 25.3 21.6 19.0 17.1 15.5 13.3 11.7 10.4 9.5

159.1 142.9 130.2 119.9 111.4 104.1 97.9 92.6 87.9 83.7 79.9 76.6 73.6 70.8 68.3 65.9 63.8 61.8 60.0 58.3 56.7 55.2 53.8 52.4 51.2 50.0 45.0 41.0 37.8 35.1 32.8 30.9 26.4 23.2 20.8 18.9 16.2 14.2 12.7 11.6

183.1 164.2 149.5 137.5 127.6 119.3 112.1 105.9 100.5 95.6 91.3 87.5 84.0 80.8 77.9 75.2 72.8 70.5 68.4 66.4 64.6 62.9 61.3 59.7 58.3 57.0 51.2 46.6 42.9 39.9 37.3 35.1 30.0 26.3 23.6 21.5 18.3 16.1 14.4 13.1

207.0 185.5 168.6 155.0 143.7 134.3 126.2 119.1 113.0 107.5 102.7 98.3 94.4 90.8 87.5 84.5 81.7 79.2 76.8 74.6 72.5 70.6 68.8 67.0 65.4 63.9 57.4 52.3 48.2 44.7 41.8 39.3 33.6 29.5 26.5 24.1 20.5 18.0 16.1 14.7

285.5 255.0 231.4 212.3 196.6 183.5 172.2 162.5 154.0 146.5 139.8 133.7 128.3 123.4 118.9 114.7 110.9 107.4 104.2 101.1 98.3 95.6 93.2 90.8 88.6 86.5 77.7 70.7 65.0 60.4 56.4 53.0 45.2 39.7 35.6 32.3 27.5 24.2 21.6 19.7

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Minutes

Hours

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

1000-yr **

300

5.00

360 420 480 540 600 660

6.00 7.00 8.00 9.00 10.00 11.00

720 780 840 900 960 1020

12.00 13.00 14.00 15.00 16.00 17.00

1080 1140 1200 1260 1320 1380

18.00 19.00 20.00 21.00 22.00 23.00

1440

24.00

4.6 4.1 3.6 3.3 3.0 2.8 2.6 2.5 2.3 2.2 2.1 2.0 1.9 1.9 1.8 1.7 1.7 1.6 1.6 1.5

6.7 5.9 5.3 4.8 4.4 4.1 3.8 3.6 3.4 3.2 3.1 2.9 2.8 2.7 2.6 2.5 2.4 2.3 2.3 2.2

8.1 7.1 6.4 5.8 5.3 5.0 4.6 4.3 4.1 3.9 3.7 3.5 3.4 3.3 3.1 3.0 2.9 2.8 2.7 2.7

9.9 8.7 7.8 7.1 6.5 6.0 5.6 5.3 5.0 4.7 4.5 4.3 4.1 4.0 3.8 3.7 3.5 3.4 3.3 3.2

11.2 9.8 8.8 8.0 7.3 6.8 6.3 6.0 5.6 5.3 5.1 4.9 4.6 4.5 4.3 4.1 4.0 3.9 3.7 3.6

12.5 11.0 9.8 8.9 8.2 7.6 7.1 6.7 6.3 6.0 5.7 5.4 5.2 5.0 4.8 4.6 4.5 4.3 4.2 4.1

16.7 14.7 13.1 11.9 11.0 10.2 9.5 8.9 8.4 8.0 7.6 7.2 6.9 6.6 6.4 6.2 5.9 5.8 5.6 5.4

** Use with discretion

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.2.5

City of Grande Prairie

Comparison of New IDF Curves with Current IDF Curves

Figure 8 shows a comparison of the proposed new City of Grande Prairie IDF curves with the current City of Grande Prairie IDF curves. Here are some observations: • For durations less than 2 hours, the new IDF curves are between 10 to 60% more intense than the current City IDF curves, depending on the duration and the return period. ▪ The new 5-year IDF curve is on average 21% more intense than the current 5-year. ▪ The new 5-year is similar to the current 10-year. ▪ The current 5-year is similar to the new 3.5-year. ▪ The new 100-year IDF curve is on average 34% more intense than the current 100year. ▪ The new 100-year is similar to the current 1500-year (extrapolated estimate). ▪ The current 100-year is similar to the new 22-year. • For durations between 2 and 24 hours, the difference between the City’s current and new curves is less that 14%. The new IDF curves are often slightly higher in intensity for all durations, except for the 24-hour duration intensity where the new curves are about 7% lower in intensity for all return periods. • In summary, compared to the current IDF curves, the new IDF curves have more intense short-duration rainfalls and similar long-duration rainfalls.

Rainfall Intensity (mm/hr)

100

New IDF 1000-yr New IDF 100-yr New IDF 50-y r

New IDF 25-yr

New IDF 10-yr New IDF 5-yr New IDF 2-yr Current IDF 100-yr Current IDF 50-yr Current IDF 25-yr Current IDF 10-yr Current IDF 5-yr

Current IDF 2-yr

1 1

100

1000

Rainfall Duration (minutes)

Figure 8: New City of Grande Prairie IDF Curves (Based on Upper 95% Confidence Interval of All 9 Stations) vs. Current City of Grande Prairie IDF curves Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.2.6

City of Grande Prairie

Comparison of New IDF Curves with City of Edmonton IDF Curves

Figure 9 shows a comparison of the new City of Grande Prairie IDF curves with the current City of Edmonton IDF curves (2015 design standards). Here are some observations: • The new City of Grande Prairie IDF curves are lower in intensity than the current City of Edmonton IDF curves, with few exceptions. • For the 2-year and 5-year curves, the new City of Grande Prairie IDF curves are very similar to the City of Edmonton ones. • For the 100-year event, the City of Edmonton IDF curve have 30% (30-minutes duration) to 70% (24-hours duration) larger intensities than the new City of Grande Prairie IDF curves, which is very significant. • For rainfall events lasting more than 30 minutes, the City of Edmonton’s 100-year IDF curve exceeds the 1000-year IDF curve of the City of Grande Prairie.

Rainfall Intensity (mm/hr)

100

New IDF 1000-yr New IDF 100-yr New IDF 50-y r

New IDF 25-y r

New IDF 10-y r New IDF 5-yr New IDF 2-yr COE (2015 DS) 100-yr COE (2015 DS) 50-yr COE (2015 DS) 25-yr COE (2015 DS) 10-yr COE (2015 DS) 5-y r

COE (2015 DS) 2-y r

1 1

100

1000

Rainfall Duration (minutes)

Figure 9: Proposed New City of Grande Prairie IDF Curves (Based on Upper 95% Confidence Interval of All 9 Stations) vs. Current City of Edmonton IDF curves

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.2.7

City of Grande Prairie

IDF Curves â&#x20AC;&#x201C; Conclusions and Recommendations

On August 2, 2012, about 42 mm of rain fell on parts of Grande Prairie within a 1-hour period and flooded several areas of the City. According to the current City IDF curves, the event was recorded as a 1:3300-year 1-hour event at one of the City gauges, and as a 1:800-year 1-hour event at another (these return periods are extrapolated estimates). Using the new IDF curves, the August 2nd event would be designated as a 1:180-year 1-hour event and a 1:75-year 1-hour event at these two gauges. This is still defined an extremely intense rainfall, but the return periods are more realistic. The new IDF curves generally have larger intensities (10 to 60% more) than the current IDF curves for the smaller durations (less than 2 hours). These high-intensity short duration rainfalls are often responsible for flooding of urban areas, as the City experienced in 2012. For durations larger than 2 hours, the new IDF curves are similar to the current curves. It is recommended that the new IDF curves presented in this section be implemented immediately and be used for the evaluation of existing drainage infrastructure, the design of new infrastructure and the planning of future infrastructure. Furthermore, the City should continue to collect and monitor rainfall data in the City and at surrounding gauges, with an objective to review and/or update the IDF curves on a regular basis.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Synthetic Design Rainfalls Events 1.3.1

Background

Many synthetic rainfall distributions have been developed and studied over the years. These distributions are generally used for computer modeling purposes. The City of Grande Prairie uses three different synthetic design rainfalls for drainage design purposes: The 4-hour Chicago Distribution, the 12-hour AES distribution and the 24-hour SCS design storms. For other Alberta municipalities: • The City of Edmonton uses the 4-hour Chicago distribution, the 24-hour Huff distribution, as well as known historical events. These rainfalls are tabulated in their design standards. • The City of Calgary uses the Chicago distribution for all events from the 1-hour to the 24-hour. These rainfalls are tabulated in their Stormwater Management & Design Manual. • The City of Red Deer uses the Chicago distribution for all rainfall events. They do not provide the tabulated values for these distributions. • The City of Medicine Hat uses both the Chicago and Huff distribution (1st and 3rd quartiles), up to the 24-hour duration event. They do not provide the tabulated values for these distributions. • The City of Fort Saskatchewan uses both the 4-hour Chicago and 24-hour Huff distribution (no mention of which quantile). They also specify the use of the 12-hour rainfall for simulation purposes. They do not provide the tabulated values for these distributions. • Many other Alberta cities do not specify which synthetic rainfall distribution to use, including the City of Lethbridge, the City of St. Albert, the City of Fort McMurray, the City of Spruce Grove, and the City of Leduc. However, most of them specify that the 4hour and 24-hour design storms should be evaluated. The Government of Alberta “Standards and Guidelines for Municipal Waterworks, Wastewater and Storm Drainage Systems – Part 5 (March 2013)” states the following: • For larger municipalities, the minor system should be designed to carry the peak flow resulting from a one in 5-year rainfall event; for several communities faced with limited financial reserves, the use of the 2-year event may be practical. For the major system, the design should be based on a one in 100-year rainfall event. • This document does not discuss or specify which design rainfall should be used for modeling purposes. The Government of Alberta “Stormwater Management Guidelines for the Province of Alberta (January 1999)” states the following: • The most commonly used synthetic method for developing design storms has been the Chicago Method. It is most suitable for analyzing urban runoff and designing sewer

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

capacities as they tend to result in high runoff peaks. They are therefore more conservative. • The document indirectly refers to the Huff distribution method as a recent investigation to develop design storm distributions that are more realistic than the Chicago hydrograph. • It also mentions about studies conducted by the Atmospheric Environment Services (AES) of Canada that analysed 35 stations across Canada for storms of 1 hour to 12 hours in duration. They indicate the 12-hour AES curves to be suitable to analyse runoff in rural areas and to size detention ponds. • The document briefly mentions about the 12-hour SCS storm distribution as a suitable method to analyze runoff from rural area and to size detention ponds.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.3.2

City of Grande Prairie

Chicago Distribution

BACKGROUND The Chicago distribution is a widely used rainfall distribution for purposes of sizing storm sewer pipes and drainage systems. This representation of the temporal distribution of rainfall was proposed by Keifer and Chu in 1957. They developed a storm pattern which would preserve the maximum volume of water falling within a specified duration, the average amount of rainfall before the peak intensity, and the relative time of the peak intensity. To determine the time distribution of rainfall and preserve the previously mentioned characteristics, they adopted the empirical IDF curves. By using IDF curves, they stayed with a procedure and concepts engineers were familiar with and is simple to obtain and therefore, it has become widely accepted for use in engineering practice and provides a reasonable basis for design.1 Although it may be considered to be somewhat too intense in the very short interval immediately around the peak of the storm, because of the way it is derived, the method is still commonly used for small to medium urbanizing watersheds (0.1 to 25 km2) where times to peak are short. These potentially unrealistically peak intensities can be offset by averaging the data into time intervals; 5 to 10 minutes is common. The Government of Alberta “Stormwater Management Guidelines for the Province of Alberta (January 1999)” suggests averaging the peak of the rainfall over 10 minutes – which is equivalent to the time of concentration of the smallest sub-basin – to avoid overestimating the peak runoff. APPLICABILITY The Chicago rainfall distribution was adopted by many U.S. and Canadian municipalities. In Alberta, the City of Edmonton uses the 4-hour Chicago distribution; and the City of Calgary uses the Chicago distribution to simulate 1-hour to 24-hour events. Many other municipalities also use the Chicago distribution. To properly develop a Chicago distribution rainfall, knowing the IDF curve parameters of the locality is necessary. Since the Chicago distribution is based on these IDF curves, its intensity for the various time steps is site specific. Chicago distributions can be developed for any duration, as long as the duration is included in the IDF curves; durations of 1 hour to 24 hours are typical.

Visual OTTHYMO v3.0 Reference Manual (October 2012) (http://www.visualotthymo.com/downloads/VH_Otthymo_Reference_Manual.pdf) 1

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

CURRENT DESIGN STANDARDS The City of Grande Prairie’s design standards provide 4-hour design storms based on the Chicago distribution. Rainfall intensities are tabulated for the 5-, 10-, 25- and 100-year storms at 5 minutes interval. Figure 10 shows these in a chart format. It should be noted that because there are two IDF curves for each return period, the City’s Chicago distributions and are not true to the IDF curves. For example, the 5-year event’s total rainfall volume based on the 4-hour Chicago distribution is 28.0 mm, but it should be 30.5 mm according to the IDF curve equation; this is an 8% difference; 28.0 mm over 4 hours is closer to 4-hour event. It should also be noted that the tabulated City’s 10-year Chicago event is actually slightly less intense than the 5-year event for the entire duration of the rainfall, with the exception of the peak 10-minutes. The total rainfall volume for that 10-year Chicago distribution is also much less than it should be (it is 28.9 mm, it should be 36.2 mm).

100 Current 4-hour Chicago 100-yr

Current 4-hour Chicago 25-yr

Current 4-hour Chicago 10-yr

Rainfall Intensity (mm/hr)

Current 4-hour Chicago 5-y r

70 60 50 40 30 20 10 0 0

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240

Rainfall Duration (minutes)

Figure 10: Current City of Grande Prairie 4-Hour Chicago Distribution Design Rainfalls

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

NEW/UPDATED DESIGN RAINFALLS AND DISCUSSIONS 4-hour and 24-hour Chicago distribution design rainfalls were developed from the new IDF equations presented above. The new 4-hour design rainfalls are illustrated in Figure 11 and tabulated in Table 6 at 5 minutes interval. The new 24-hour design rainfalls are illustrated in Figure 12 and tabulated in Table 7 at 15 minutes interval. For any other rainfall duration, the peak values of the 4-hour or 24-hour Chicago distribution can be used. For example, the 12-hour distribution can be derived by taking the 24-hour distribution values from 4.25 to 16.00 hours, as highlighted in yellow in Table 7. Figure 13 compares the new 4-hour Chicago distributions with the current 4-hour distributions for the 5-year and 100-year events. The main difference between them is at the peak 30 minutes of the rainfall; the new distributions have higher peak intensities, while the current distributions have a more spread out peak. Of note, the peak 10 minutes of the new 5-year and 100-year distribution are 30% and 42% more intense than the current distributions, respectively. This is quite significant and could greatly impact the design of storm sewer systems.

180 New 4-hour Chicago 100-yr

New 4-hour Chicago 50-y r

160

New 4-hour Chicago 25-y r New 4-hour Chicago 10-y r

Rainfall Intensity (mm/hr)

140

New 4-hour Chicago 5-yr

New 4-hour Chicago 2-yr

120 100 80 60 40 20 0 0

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240

Rainfall Duration (minutes)

Figure 11: New City of Grande Prairie 4-Hour Chicago Distribution Design Rainfalls (discretized at 5 minutes interval)

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

80 New 24-hour Chicago 100-yr New 24-hour Chicago 50-yr

New 24-hour Chicago 25-yr

New 24-hour Chicago 10-yr New 24-hour Chicago 5-y r

Rainfall Intensity (mm/hr)

New 24-hour Chicago 2-y r

50 40 30 20 10 0 0

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rainfall Duration (hours)

Figure 12: New City of Grande Prairie 24-Hour Chicago Distribution Design Rainfalls (discretized at 15 minutes interval)

180 New 4-hour Chicago 5-yr

New 4-hour Chicago 100-yr

160 Current 4-hour Chicago 5-yr

Current 4-hour Chicago 100-yr

Rainfall Intensity (mm/hr)

140

60 50 40 30

120 100 80 60

20 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240

0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240

Rainfall Intensity (mm/hr)

Rainfall Duration (minutes)

Figure 13: New City of Grande Prairie 4-Hour Chicago Distribution Design Rainfalls vs. Current for the 5-year (left) and 100-year (right) Events

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 6: New City of Grande Prairie 4-Hour Chicago Distribution Design Rainfall, in mm/hr Minutes

Hours

5 10 15 20 25 30 35 40 45 50 55 60 65

1.00

70 75 80 ** 85 ** 90 95 100 105 110 115 120 125 130 135

2.00

140 145 150 155 160 165 170 175 180 185

3.00

2-yr

5-yr

10-yr

1.6 1.7 1.8 1.9 2.0 2.2 2.3 2.5 2.8 3.1 3.5 4.1 5.0 6.5 10.0 35.5 (44.3) 53.1 (44.3) 17.8 11.4 8.6 7.0 6.0 5.3 4.7 4.3 3.9 3.6 3.4 3.2 3.0 2.9 2.7 2.6 2.5 2.4 2.3 2.2

2.3 2.4 2.6 2.7 2.9 3.1 3.3 3.6 4.0 4.4 5.0 5.8 7.0 9.2 14.0 52.9 (67.0) 81.1 (67.0) 24.6 15.9 12.1 9.9 8.4 7.4 6.7 6.1 5.6 5.2 4.8 4.5 4.3 4.1 3.9 3.7 3.5 3.4 3.3 3.1

2.8 3.0 3.1 3.3 3.5 3.7 4.0 4.4 4.8 5.3 6.0 7.0 8.5 11.0 16.7 64.9 (82.7) 100.4 (82.7) 29.3 18.9 14.4 11.8 10.1 8.9 8.0 7.3 6.7 6.2 5.8 5.5 5.2 4.9 4.7 4.5 4.3 4.1 4.0 3.8

Sameng Inc.

25-yr

50-yr

3.4 3.8 3.6 4.0 3.8 4.2 4.0 4.5 4.2 4.8 4.5 5.1 4.9 5.5 5.3 5.9 5.8 6.5 6.5 7.2 7.3 8.2 8.5 9.5 10.2 11.5 13.3 14.9 20.1 22.6 79.9 91.3 (102.4) (117.3) 124.8 143.2 (102.4) (117.3) 35.1 39.5 22.8 25.6 17.4 19.5 14.3 16.1 12.3 13.8 10.8 12.1 9.7 10.9 8.8 9.9 8.1 9.1 7.5 8.5 7.1 7.9 6.6 7.4 6.3 7.0 5.9 6.7 5.7 6.3 5.4 6.1 5.2 5.8 5.0 5.6 4.8 5.4 4.6 5.2

100-yr

4.3 4.5 4.7 5.0 5.3 5.7 6.1 6.6 7.3 8.1 9.2 10.6 12.8 16.6 25.2 102.7 (132.1) 161.4 (132.1) 43.9 28.5 21.8 17.9 15.4 13.5 12.2 11.1 10.2 9.5 8.8 8.3 7.9 7.5 7.1 6.8 6.5 6.2 6.0 5.8

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo Minutes

Hours

190 195 200 205 210 215 220 225 230 235 240 4.00 4-Hour Precipitation Total (mm) 2-Hour Precipitation Total (mm)

City of Grande Prairie 2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

2.1 2.1 2.0 1.9 1.9 1.8 1.8 1.7 1.7 1.6 1.6

3.0 2.9 2.8 2.8 2.7 2.6 2.5 2.5 2.4 2.4 2.3

3.7 3.6 3.4 3.3 3.2 3.2 3.1 3.0 2.9 2.9 2.8

4.5 4.3 4.2 4.1 3.9 3.8 3.7 3.6 3.5 3.5 3.4

5.0 4.8 4.7 4.5 4.4 4.3 4.2 4.1 4.0 3.9 3.8

5.6 5.4 5.2 5.1 4.9 4.8 4.7 4.5 4.4 4.3 4.2

21.6

31.3

38.0

46.3

52.4

58.7

17.6

25.5

31.0

37.9

42.9

48.1

** Values in blue are average intensities over peak 10 minutes period. Yellow highlight is peak 2-hour of Chicago rainfall distribution.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 7: New City of Grande Prairie 24-Hour Chicago Distribution Design Rainfall, in mm/hr Hours

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.00 0.25 0.50 0.75 1.00 1.25

0.00 0.44 0.45 0.46 0.48 0.49 0.50 0.51 0.53 0.55 0.56 0.58 0.60 0.62 0.65 0.67 0.70 0.74 0.77 0.81 0.86 0.91 0.97 1.05 1.13 1.24 1.38 1.56 1.81 2.18 2.80 4.20 17.34 27.45 7.22 4.74 3.65 3.02 2.59

0.00 0.63 0.65 0.66 0.68 0.70 0.72 0.74 0.76 0.78 0.81 0.83 0.86 0.89 0.93 0.97 1.01 1.05 1.11 1.16 1.23 1.31 1.40 1.50 1.63 1.78 1.97 2.23 2.58 3.11 4.00 5.95 25.33 40.53 10.12 6.71 5.18 4.29 3.70

0.00 0.77 0.79 0.81 0.83 0.85 0.87 0.89 0.92 0.95 0.98 1.01 1.05 1.08 1.13 1.17 1.22 1.28 1.34 1.41 1.49 1.58 1.69 1.82 1.97 2.16 2.39 2.70 3.13 3.76 4.83 7.17 30.85 49.56 12.15 8.08 6.26 5.19 4.47

0.00 0.93 0.95 0.98 1.00 1.03 1.05 1.08 1.12 1.15 1.19 1.23 1.27 1.31 1.37 1.42 1.48 1.55 1.63 1.71 1.81 1.92 2.05 2.20 2.39 2.61 2.90 3.27 3.79 4.56 5.85 8.67 37.77 60.89 14.65 9.77 7.57 6.28 5.42

0.00 1.04 1.06 1.09 1.11 1.14 1.17 1.21 1.24 1.28 1.32 1.36 1.41 1.46 1.52 1.58 1.65 1.73 1.81 1.91 2.02 2.14 2.29 2.46 2.67 2.92 3.24 3.66 4.24 5.10 6.55 9.73 42.94 69.43 16.46 10.97 8.49 7.04 6.07

0.00 1.16 1.19 1.22 1.25 1.28 1.31 1.35 1.39 1.43 1.48 1.53 1.58 1.64 1.70 1.77 1.85 1.93 2.03 2.14 2.26 2.40 2.56 2.76 2.99 3.27 3.63 4.10 4.74 5.71 7.33 10.88 48.16 77.95 18.36 12.25 9.50 7.87 6.79

1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 5.50 5.75 6.00 6.25 6.50 6.75 7.00 7.25 7.50 7.75 8.00 8.25 8.50 8.75 9.00 9.25 9.50

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Hours

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

9.75

2.29 2.06 1.88 1.73 1.61 1.51 1.42 1.34 1.27 1.21 1.16 1.11 1.07 1.03 0.99 0.96 0.93 0.90 0.87 0.85 0.82 0.80 0.78 0.76 0.74 0.73 0.71 0.70 0.68 0.67 0.65 0.64 0.63 0.62 0.61 0.60 0.59 0.58 0.57 0.56 0.55

3.27 2.94 2.69 2.48 2.30 2.16 2.03 1.92 1.82 1.74 1.66 1.59 1.53 1.47 1.42 1.37 1.33 1.29 1.25 1.21 1.18 1.15 1.12 1.09 1.07 1.04 1.02 1.00 0.98 0.96 0.94 0.92 0.90 0.89 0.87 0.86 0.84 0.83 0.81 0.80 0.79

3.96 3.56 3.25 3.00 2.79 2.61 2.46 2.33 2.21 2.10 2.01 1.93 1.85 1.78 1.72 1.66 1.61 1.56 1.51 1.47 1.43 1.39 1.36 1.32 1.29 1.26 1.24 1.21 1.18 1.16 1.14 1.12 1.09 1.07 1.06 1.04 1.02 1.00 0.99 0.97 0.96

4.79 4.32 3.94 3.64 3.38 3.17 2.98 2.82 2.68 2.55 2.44 2.34 2.25 2.16 2.09 2.02 1.95 1.89 1.84 1.78 1.73 1.69 1.65 1.61 1.57 1.53 1.50 1.47 1.44 1.41 1.38 1.35 1.33 1.30 1.28 1.26 1.24 1.22 1.20 1.18 1.16

5.37 4.83 4.41 4.07 3.78 3.54 3.33 3.15 2.99 2.85 2.72 2.61 2.51 2.41 2.33 2.25 2.18 2.11 2.05 1.99 1.93 1.88 1.84 1.79 1.75 1.71 1.67 1.63 1.60 1.57 1.54 1.51 1.48 1.45 1.42 1.40 1.38 1.35 1.33 1.31 1.29

6.01 5.41 4.94 4.55 4.23 3.96 3.73 3.53 3.35 3.19 3.05 2.92 2.81 2.70 2.61 2.52 2.44 2.36 2.29 2.23 2.17 2.11 2.06 2.00 1.96 1.91 1.87 1.83 1.79 1.75 1.72 1.69 1.65 1.62 1.60 1.57 1.54 1.52 1.49 1.47 1.44

10.00 10.25 10.50 10.75 11.00 11.25 11.50 11.75 12.00 12.25 12.50 12.75 13.00 13.25 13.50 13.75 14.00 14.25 14.50 14.75 15.00 15.25 15.50 15.75 16.00 16.25 16.50 16.75 17.00 17.25 17.50 17.75 18.00 18.25 18.50 18.75 19.00 19.25 19.50 19.75

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Hours

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

20.00

0.54 0.53 0.53 0.52 0.51 0.50 0.50 0.49 0.48 0.48 0.47 0.47 0.46 0.46 0.45 0.44 0.44

0.78 0.76 0.75 0.74 0.73 0.72 0.71 0.70 0.69 0.69 0.68 0.67 0.66 0.65 0.65 0.64 0.63

0.94 0.93 0.91 0.90 0.89 0.88 0.86 0.85 0.84 0.83 0.82 0.81 0.80 0.79 0.78 0.77 0.76

1.14 1.12 1.11 1.09 1.08 1.06 1.05 1.03 1.02 1.01 0.99 0.98 0.97 0.96 0.95 0.94 0.93

1.27 1.25 1.23 1.22 1.20 1.18 1.17 1.15 1.14 1.12 1.11 1.09 1.08 1.07 1.05 1.04 1.03

1.42 1.40 1.38 1.36 1.34 1.32 1.31 1.29 1.27 1.26 1.24 1.22 1.21 1.20 1.18 1.17 1.15

36.4

52.5

63.7

77.4

87.1

97.5

29.8

43.0

52.2

63.5

71.6

80.2

20.25 20.50 20.75 21.00 21.25 21.50 21.75 22.00 22.25 22.50 22.75 23.00 23.25 23.50 23.75 24.00 24-hour Precipitation Total (mm) 12-hour Precipitation Total (mm)

Yellow highlight is peak 12-hour of Chicago rainfall distribution.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.3.3

City of Grande Prairie

AES Distribution (Atmospheric Environment Services)

BACKGROUND The Canadian Atmospheric Environment Service (AES) examined the temporal variation of rainfall using close to 2000 extreme events in Canada. Hogg (1980) conducted the analysis of the time distribution of rainfall in short duration events. Rainfall duration of 1 and 12 hours were selected for the analysis. The temporal distribution patterns were found to vary in the different regions of Canada.2 APPLICABILITY We could not find publication of the AES rainfall distributions. We also could not find any Alberta municipalities, other than the City of Grande Prairie, that use the AES distribution. The Government of Alberta’s 1999 “Stormwater Management Guidelines for the Province of Alberta” mentioned the existence of the 12-hour AES distribution, but it is not shown. In summary, the AES distribution does not appear to be common. To develop a 12-hour AES distribution, the only information needed is the total volume of rainfall over that 12-hour period. In other words, the distribution is not site specific, but at least it was derived based on Canadian rainfall data. CURRENT DESIGN STANDARDS The City of Grande Prairie’s design standards provide a tabulated version of the 12-hour AES design rainfall. Rainfall intensities are tabulated for the 100-year storm at 1-hour intervals. Figure 14 shows that table and the values in a chart format. It should be noted that the total rainfall volume based on the 12-hour storm design table is 76.6 mm, but it should be 80.8 mm according to the IDF curve equation; this is a 5% difference. Consequently, the AES table provided in the City’s design standards is representative of a 75-year 12-hour rainfall event, not a 100-year event.

Visual OTTHYMO v3.0 Reference Manual (October 2012) (http://www.visualotthymo.com/downloads/VH_Otthymo_Reference_Manual.pdf) 2

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

30 Current 12-hour AES 100-yr

Rainfall Intensity (mm/hr)

0 0

Rainfall Duration (hours)

Figure 14: Current 100-Year City of Grande Prairie 12-Hour AES Design Rainfall

NEW/UPDATED DESIGN RAINFALLS AND DISCUSSIONS Based on the discrete rainfall percentages for the 12-hour AES design storm (as provided in the City of Grande Prairie design standards) and the total 12-hour rainfall depth from the new IDF curves, the AES rainfall distribution was updated. The following Figure 15 shows the new 12-hour AES design rainfall overlaid by the current distribution; Table 8 shows the tabulated results. The new distribution is more intense and has more volume than the current one, but the difference is small.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

30 NEW 12-hour AES 100-yr Current 12-hour AES 100-yr

Rainfall Intensity (mm/hr)

0 0

Rainfall Duration (hours)

Figure 15: New 100-Year City of Grande Prairie 12-Hour AES Distribution Design Rainfall vs. Current Table 8: New City of Grande Prairie 12-Hour AES Distribution Design Rainfall, in mm/hr Hours

Discrete Rainfall (%)

18%

33%

16%

11%

12-hour Precipitation Total (mm)

Sameng Inc.

100-yr

0.00 0.80 4.01 14.44 26.47 12.83 8.82 5.61 3.21 1.60 0.80 0.80 0.80 80.2

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.3.4

City of Grande Prairie

SCS Distribution (U.S. Soil Conservation Services)

BACKGROUND The U.S. Soil Conservation Service (SCS) analyzed rainfall across the U.S. and determined the mass curve for percent of accumulated rainfall depth over a duration of 6 hours (1975) and 24 hours (1986). For the 24-hour duration, SCS characterized the rainfall using 4 types of storm patterns, applicable to different regions of the U.S. The Type II rainfall distribution applies to most of the continental U.S. In Canada, the Type II curve applies in most areas, however, there are some regions in British Columbia where the Type I curve is used. 3 4 The 24-hour SCS Type II curve is shown in Figure 16.

Cumulative Fraction of Storm Depth

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0

Rainfall Duration (Hours)

Figure 16: 24-hour SCS Type II Distribution

Singh, V.P. â&#x20AC;&#x2DC;Elementary Hydrologyâ&#x20AC;&#x2122;, Prentice Hall, Upper Saddle River, New Jersey, 1992.

Visual OTTHYMO v3.0 Reference Manual (October 2012) (http://www.visualotthymo.com/downloads/VH_Otthymo_Reference_Manual.pdf) 4

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

APPLICABILITY We are not aware of Alberta municipalities, other than the City of Grande Prairie, using the SCS rainfall distributions for design purposes. Some documentation from the U.S. recommended to stop using the SCS distributions for both urban and rural areas and use the NOAA Atlas 14 derived rainfall distributions instead (the first versions of Atlas 14 were developed in 2004). The Atlas 14 rainfall distributions and rainfall depths are continually updated using many years of data from many stations and are much more site specific. In a way, Atlas 14 is similar to the Chicago distribution, where site specific information is used to derive the rainfall distribution. However, the intensities/depth for various return periods are not determined from an equation, but from actual measurements and frequency analysis. Most of the U.S. has now switched to the Atlas 14 distribution, but some are still using the SCS method. Atlas 14 is U.S. specific. The SCS distribution gives results that are similar to the Chicago distribution in terms of peak intensity and shape. However, the SCS distribution is not site specific; it does not require IDF curve parameters. It is based solely on total rainfall depth; therefore, the larger the rainfall depth, the larger the intensity. SCS distributions can be developed for any duration with some adjustments to the ‘Accumulated Depth’ value. CURRENT DESIGN STANDARDS The City of Grande Prairie’s design standards provide a tabulated version of the 24-hour SCS design rainfall. Rainfall intensities are tabulated for the 100-year storm at 0.2 hours interval. Figure 17 shows the chart. It should be noted that the totaI rainfall volume based on the 24-hour storm design table is 100.6 mm, but it should be 103.6 mm according to the IDF curve equation; this is a 3% difference. Consequently, the SCS table provided in the City’s design standards is representative of an 85-year 24-hour rainfall event, not a 100-year event.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

140 Current 24-hour SCS Type II 100-yr

Rainfall Intensity (mm/hr)

120

100

0 0

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rainfall Duration (hours)

Figure 17: Current 100-Year City of Grande Prairie 24-Hour SCS Type II Design Rainfall

NEW/UPDATED DESIGN RAINFALLS AND DISCUSSIONS The SCS Type II rainfall distribution was updated based on the total 24-hour rainfall depth from the new IDF equations. The new 24-hour design rainfalls are illustrated in Figure 18 and tabulated in Table 8 at 15 minutes interval. Figure 19 compares the new 24-hour SCS Type II distributions with the current 24-hour distribution for the 100-year event. The new distribution is slightly less intense and has less volume than the current one, but the difference is small. This is because the 24-hour rainfall volume derived from the new IDF equations is less than the current design standards.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

120 New 24-hour SCS TYPE II 100-yr New 24-hour SCS TYPE II 50-y r New 24-hour SCS TYPE II 25-y r

100

New 24-hour SCS TYPE II 10-y r

Rainfall Intensity (mm/hr)

New 24-hour SCS TYPE II 5-yr New 24-hour SCS TYPE II 2-yr

0 0

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rainfall Duration (hours)

Figure 18: New City of Grande Prairie 24-Hour SCS Type II Distribution Design Rainfalls 120 New 24-hour SCS TYPE II 100-yr Current SCS Ty pe II 100-yr

Rainfall Intensity (mm/hr)

100

0 0

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rainfall Duration (hours)

Figure 19: New City of Grande Prairie 24-Hour SCS Type II Distribution Design Rainfalls vs. Current for the 100-Year Event

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 9: New City of Grande Prairie 24-Hour SCS Type II Design Storm, in mm/hr

0.00 0.25 0.50 0.75

mm/hr for 1mm of total precipitation 0.0000 0.0100 0.0104 0.0106

1.00 1.25 1.50 1.75 2.00 2.25 2.50

0.0110 0.0110 0.0114 0.0116 0.0120 0.0122 0.0122

2.75 3.00 3.25 3.50 3.75 4.00

0.0126 0.0130 0.0130 0.0134 0.0138 0.0138

4.25 4.50 4.75 5.00 5.25 5.50

0.0142 0.0150 0.0150 0.0158 0.0162 0.0166

5.75 6.00 6.25 6.50 6.75 7.00

0.0174 0.0178 0.0182 0.0186 0.0194 0.0198

7.25 7.50 7.75 8.00 8.25 8.50

0.0202 0.0210 0.0210 0.0218 0.0232 0.0256

8.75 9.00 9.25 9.50

0.0286 0.0306 0.0320 0.0320

Hours

Accumulated Depth (%)

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.0000 0.0025 0.0051 0.0078 0.0105 0.0133 0.0161 0.0190 0.0220 0.0251 0.0281 0.0313 0.0345 0.0378 0.0411 0.0446 0.0480 0.0516 0.0553 0.0591 0.0630 0.0671 0.0712 0.0756 0.0800 0.0846 0.0892 0.0941 0.0990 0.1041 0.1093 0.1146 0.1200 0.1258 0.1322 0.1394 0.1470 0.1550 0.1630

0.00 0.36 0.38 0.39 0.40 0.40 0.41 0.42 0.44 0.44 0.44 0.46 0.47 0.47 0.49 0.50 0.50 0.52 0.55 0.55 0.58 0.59 0.60 0.63 0.65 0.66 0.68 0.71 0.72 0.74 0.76 0.76 0.79 0.84 0.93 1.04 1.11 1.16 1.16

0.00 0.53 0.55 0.56 0.58 0.58 0.60 0.61 0.63 0.64 0.64 0.66 0.68 0.68 0.70 0.72 0.72 0.75 0.79 0.79 0.83 0.85 0.87 0.91 0.93 0.96 0.98 1.02 1.04 1.06 1.10 1.10 1.14 1.22 1.34 1.50 1.61 1.68 1.68

0.00 0.64 0.66 0.68 0.70 0.70 0.73 0.74 0.76 0.78 0.78 0.80 0.83 0.83 0.85 0.88 0.88 0.90 0.96 0.96 1.01 1.03 1.06 1.11 1.13 1.16 1.18 1.24 1.26 1.29 1.34 1.34 1.39 1.48 1.63 1.82 1.95 2.04 2.04

0.00 0.77 0.80 0.82 0.85 0.85 0.88 0.90 0.93 0.94 0.94 0.98 1.01 1.01 1.04 1.07 1.07 1.10 1.16 1.16 1.22 1.25 1.28 1.35 1.38 1.41 1.44 1.50 1.53 1.56 1.63 1.63 1.69 1.80 1.98 2.21 2.37 2.48 2.48

0.00 0.87 0.91 0.92 0.96 0.96 0.99 1.01 1.05 1.06 1.06 1.10 1.13 1.13 1.17 1.20 1.20 1.24 1.31 1.31 1.38 1.41 1.45 1.52 1.55 1.59 1.62 1.69 1.72 1.76 1.83 1.83 1.90 2.02 2.23 2.49 2.67 2.79 2.79

0.00 0.98 1.01 1.03 1.07 1.07 1.11 1.13 1.17 1.19 1.19 1.23 1.27 1.27 1.31 1.35 1.35 1.38 1.46 1.46 1.54 1.58 1.62 1.70 1.74 1.77 1.81 1.89 1.93 1.97 2.05 2.05 2.13 2.26 2.50 2.79 2.98 3.12 3.12

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

9.75 10.00 10.25 10.50 10.75

mm/hr for 1mm of total precipitation 0.0340 0.0380 0.0432 0.0488 0.0572

11.00 11.25 11.50 11.75 12.00 12.25

0.0668 0.0844 0.1076 0.4384 1.0816 0.1712

12.50 12.75 13.00 13.25 13.50 13.75

0.1168 0.0804 0.0676 0.0572 0.0508 0.0444

14.00 14.25 14.50 14.75 15.00 15.25

0.0396 0.0362 0.0342 0.0328 0.0308 0.0292

15.50 15.75 16.00 16.25 16.50 16.75

0.0272 0.0258 0.0238 0.0226 0.0222 0.0214

17.00 17.25 17.50 17.75 18.00 18.25

0.0210 0.0200 0.0196 0.0188 0.0184 0.0176

18.50 18.75 19.00 19.25 19.50 19.75

0.0172 0.0164 0.0156 0.0154 0.0146 0.0138

Hours

City of Grande Prairie

Accumulated Depth (%)

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.1715 0.1810 0.1918 0.2040 0.2183 0.2350 0.2561 0.2830 0.3926 0.6630 0.7058 0.7350 0.7551 0.7720 0.7863 0.7990 0.8101 0.8200 0.8291 0.8376 0.8458 0.8535 0.8608 0.8676 0.8741 0.8800 0.8857 0.8912 0.8966 0.9018 0.9068 0.9117 0.9164 0.9210 0.9254 0.9297 0.9338 0.9377 0.9416 0.9452 0.9487

1.24 1.38 1.57 1.78 2.08 2.43 3.07 3.92 15.96 39.37 6.23 4.25 2.93 2.46 2.08 1.85 1.62 1.44 1.32 1.24 1.19 1.12 1.06 0.99 0.94 0.87 0.82 0.81 0.78 0.76 0.73 0.71 0.68 0.67 0.64 0.63 0.60 0.57 0.56 0.53 0.50

1.79 2.00 2.27 2.56 3.00 3.51 4.43 5.65 23.02 56.78 8.99 6.13 4.22 3.55 3.00 2.67 2.33 2.08 1.90 1.80 1.72 1.62 1.53 1.43 1.35 1.25 1.19 1.17 1.12 1.10 1.05 1.03 0.99 0.97 0.92 0.90 0.86 0.82 0.81 0.77 0.72

2.17 2.42 2.75 3.11 3.64 4.26 5.38 6.85 27.93 68.90 10.91 7.44 5.12 4.31 3.64 3.24 2.83 2.52 2.31 2.18 2.09 1.96 1.86 1.73 1.64 1.52 1.44 1.41 1.36 1.34 1.27 1.25 1.20 1.17 1.12 1.10 1.04 0.99 0.98 0.93 0.88

2.63 2.94 3.34 3.78 4.43 5.17 6.53 8.33 33.93 83.72 13.25 9.04 6.22 5.23 4.43 3.93 3.44 3.07 2.80 2.65 2.54 2.38 2.26 2.11 2.00 1.84 1.75 1.72 1.66 1.63 1.55 1.52 1.46 1.42 1.36 1.33 1.27 1.21 1.19 1.13 1.07

2.96 3.31 3.76 4.25 4.98 5.82 7.35 9.37 38.18 94.21 14.91 10.17 7.00 5.89 4.98 4.42 3.87 3.45 3.15 2.98 2.86 2.68 2.54 2.37 2.25 2.07 1.97 1.93 1.86 1.83 1.74 1.71 1.64 1.60 1.53 1.50 1.43 1.36 1.34 1.27 1.20

3.31 3.71 4.21 4.76 5.58 6.51 8.23 10.49 42.74 105.46 16.69 11.39 7.84 6.59 5.58 4.95 4.33 3.86 3.53 3.33 3.20 3.00 2.85 2.65 2.52 2.32 2.20 2.16 2.09 2.05 1.95 1.91 1.83 1.79 1.72 1.68 1.60 1.52 1.50 1.42 1.35

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

20.00 20.25 20.50 20.75 21.00

mm/hr for 1mm of total precipitation 0.0134 0.0130 0.0126 0.0128 0.0124

21.25 21.50 21.75 22.00 22.25 22.50

0.0126 0.0122 0.0124 0.0120 0.0120 0.0116

Hours

22.75 23.00 23.25 23.50 23.75 24.00

Accumulated Depth (%)

0.9520 0.9553 0.9584 0.9616 0.9647 0.9679 0.9709 0.9740 0.9770 0.9800 0.9829 0.9859 0.9887 0.9916 0.9944 0.9973 1.0000

0.0118 0.0114 0.0116 0.0112 0.0114 0.0110 24-hour Precipitation Total (mm)

Sameng Inc.

City of Grande Prairie 2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.49 0.47 0.46 0.47 0.45 0.46 0.44 0.45 0.44 0.44 0.42 0.43 0.41 0.42 0.41 0.41 0.40 36.4

0.70 0.68 0.66 0.67 0.65 0.66 0.64 0.65 0.63 0.63 0.61 0.62 0.60 0.61 0.59 0.60 0.58 52.5

0.85 0.83 0.80 0.82 0.79 0.80 0.78 0.79 0.76 0.76 0.74 0.75 0.73 0.74 0.71 0.73 0.70 63.7

1.04 1.01 0.98 0.99 0.96 0.98 0.94 0.96 0.93 0.93 0.90 0.91 0.88 0.90 0.87 0.88 0.85 77.4

1.17 1.13 1.10 1.11 1.08 1.10 1.06 1.08 1.05 1.05 1.01 1.03 0.99 1.01 0.98 0.99 0.96 87.1

1.31 1.27 1.23 1.25 1.21 1.23 1.19 1.21 1.17 1.17 1.13 1.15 1.11 1.13 1.09 1.11 1.07 97.5

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.3.5

City of Grande Prairie

Huff Distribution

BACKGROUND Huff (1967) examined storm patterns for midwestern U.S. watersheds. He divided the storms into 4 equal probability groups (4 quartiles) depending on the time period in which the majority of the rain occurred. The first quartile represented the most severe storms and the fourth quartile the mildest storms. The rainfall mass curves in each quartile group were determined for various probability levels. 5 6 The 50% probability curve for each quartile are illustrated in Figure 20 and Figure 21. The 1st quartile storms tend to have duration of 6 hours or less, the 2nd quartile 6 to 12 hours, the 3rd quartile 12 to 24 hours, and the 4th quartile greater than 24 hours (Huff and Angel, 1992) 7 When compared to the SCS Type II distribution and the new Chicago distribution (developed for City of Grande Prairie), the Huff distributions have a noticeably smaller peak intensity and the rainfall volume is more spread out over the entire duration of the rainfall (Figure 21).

Singh, V.P. 1992. â&#x20AC;&#x2DC;Elementary Hydrologyâ&#x20AC;&#x2122;, Prentice Hall, Upper Saddle River, New Jersey.

Visual OTTHYMO v3.0 Reference Manual (October 2012) (http://www.visualotthymo.com/downloads/VH_Otthymo_Reference_Manual.pdf) 6

Huff, F. A., and J. R. Angel. 1992. Rainfall Frequency Atlas of the Midwest. Illinois State Water Survey, Champaign, Bulletin 71. 7

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Cumulative Fraction of Storm Depth

0.9 0.8 0.7 0.6 0.5 0.4

Huff - 1st Quartile Huff - 2nd Quartile Huff - 3rd Quartile Huff - 4th Quartile SCS Type II New 24-hour Chicago 100-yr

0.3 0.2 0.1 0 0

Rainfall Duration (Hours)

Figure 20: 24-hour Huff Distribution and SCS Type II Distribution – Cumulative Rainfall Depth 0.3

Fraction of Storm Depth by 15 minutes Time Step

Huff - 1st Quartile Huff - 2nd Quartile 0.25

Huff - 3rd Quartile Huff - 4th Quartile SCS Type II

0.2

New 24-hour Chicago 100-yr

0.15

0.1

0.05

0 0

Rainfall Duration (Hours)

Figure 21: 24-hour Huff Distribution and SCS Type II Distribution – Fraction of Rainfall Depth by 15 minutes Time Step

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

APPLICABILITY The City of Grande Prairie’s design standards do not include the Huff Distribution. If the City of Grande Prairie was to consider the Huff Distribution as a design rainfall, we recommend that the 12-hour and 24-hour Huff distribution be used, mainly to size storm ponds, but also to evaluate the drainage system’s capacity (minor and minor systems) during significantly large long-duration events. The City of Edmonton uses a variation of the 1st quartile (slightly skewed towards the 2nd quartile) of the 24-hour Huff distribution for pond sizing purposes. A few other Alberta municipalities also use the Huff distribution such as Medicine Hat (1st and 3rd quartiles) and the City of Fort Saskatchewan (quartile not specified). A preliminary review of historical 24-hour duration rainfalls in the Grande Prairie area suggests that the 2nd quartile of the Huff distribution is a suitable distribution for the 24-hour event. Nevertheless, a more detailed study should be completed to confirm which quartile distribution is the most adequate. The Huff distribution is not site specific. The only parameters required are the total rainfall intensity and duration of rainfall. Also, a quartile must be selected. NEW DESIGN RAINFALLS AND DISCUSSIONS Huff Distribution (1st and 2nd quartile) rainfall distributions were developed based on the total 12-hour and 24-hour rainfall depth from the new IDF equations. The new 12-hour Huff Distribution (1st quartile) design rainfalls is shown in Figure 22, the 12-hour (2nd quartile) in Figure 23, the 24-hour (1st quartile) in Figure 24 and the 24-hour (2nd quartile) in Figure 25. Table 10 to Table 13 shows the tabulated results for these four design rainfalls, respectively. Figure 26 compare the new 12-hour distributions with one another for the 100-year event. Here are some observations: • The AES distribution has higher peak intensities than the Huff distribution, while the Huff distribution rainfall is spread out over a longer period. Nevertheless, they both have a similar shape, with most of the rainfall applied earlier in the rainfall. The peak intensity of the AES distribution is about halfway between the Huff’s 1st and 2nd quartiles. Figure 27 compare the new 24-hour distributions with one another for the 100-year event. Here are some observations: • The SCS distribution has much higher peak intensities than the Huff distribution, with 38% of the rainfall falling within 30 minutes and 50% of the rainfall within 1.5 hours. For the Huff distribution, only 5% of the total rainfall fell during the peak 30 minutes period of the rainfall, and 50% of the rainfall falling within a 6 hours period. • The Chicago distribution also has large peak intensities, but not as much as the SCS distribution. 32% of the rainfall is falling within 30 minutes and 50% of the rainfall within

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

2.25 hours. The peak of the Chicago distribution is also skewed earlier in the rainfall, while the SCS distribution peak is centered. â&#x20AC;˘ For the Huff distribution (1st quartile), the peak intensity and the bulk of the rainfall volume happens earlier in the rainfall compared to the Huffâ&#x20AC;&#x2122;s 2nd quartile, Chicago and SCS distributions.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

25 New 12-hour Huff (1st quart ile) 100-y r New 12-hour Huff (1st quart ile) 50-yr New 12-hour Huff (1st quart ile) 25-yr

New 12-hour Huff (1st quart ile) 10-yr

Rainfall Intensity (mm/hr)

New 12-hour Huff (1st quart ile) 5-yr New 12-hour Huff (1st quart ile) 2-yr

0 0

Rainfall Duration (hours)

Figure 22: New City of Grande Prairie 12-Hour Huff Distribution (1st quartile) Design Rainfalls

25 New 12-hour Huff (2nd quart ile) 100-yr New 12-hour Huff (2nd quart ile) 50-yr New 12-hour Huff (2nd quart ile) 25-yr

New 12-hour Huff (2nd quart ile) 10-yr

Rainfall Intensity (mm/hr)

New 12-hour Huff (2nd quart ile) 5-yr New 12-hour Huff (2nd quart ile) 2-yr

0 0

Rainfall Duration (hours)

Figure 23: New City of Grande Prairie 12-Hour Huff Distribution (2nd quartile) Design Rainfalls Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

14 New 24-hour Huff 100-y r New 24-hour Huff 50-yr

New 24-hour Huff 25-yr

New 24-hour Huff 10-yr

Rainfall Intensity (mm/hr)

New 24-hour Huff 5-yr

New 24-hour Huff 2-yr

0 0

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rainfall Duration (hours)

Figure 24: New City of Grande Prairie 24-Hour Huff Distribution (1st quartile) Design Rainfalls

14 New 24-hour Huff (2nd quart ile) 100-yr New 24-hour Huff (2nd quart ile) 50-yr

New 24-hour Huff (2nd quart ile) 25-yr

New 24-hour Huff (2nd quart ile) 10-yr

Rainfall Intensity (mm/hr)

New 24-hour Huff (2nd quart ile) 5-yr

New 24-hour Huff (2nd quart ile) 2-yr

0 0

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rainfall Duration (hours)

Figure 25: New City of Grande Prairie 24-Hour Huff Distribution (2nd quartile) Design Rainfalls Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

30 New 12-hour Huff (1st quart ile) 100-y r

New 12-hour Huff (2nd quart ile) 100-yr NEW 12-hour AES 100-yr

Rainfall Intensity (mm/hr)

0 0

Rainfall Duration (hours)

Figure 26: Comparison of New City of Grande Prairie 12-Hour Distributions

110 New 24-hour Huff (1st quart ile) 100-y r

100

New 24-hour Huff (2nd quart ile) 100-yr

New 24-hour SCS TYPE II 100-yr

Rainfall Intensity (mm/hr)

New 24-hour Chicago 100-yr

80 70 60 50 40 30 20 10 0 0

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rainfall Duration (hours)

Figure 27: Comparison of New City of Grande Prairie 24-Hour Distributions

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 10: New City of Grande Prairie 12-Hour Huff (1st quartile) Design Storm, in mm/hr

0.00 0.25 0.50 0.75

mm/hr for 1mm of total precipitation 0.0000 0.0725 0.1315 0.1659

1.00 1.25 1.50 1.75 2.00 2.25

0.2031 0.2400 0.2625 0.2792 0.2823 0.2619

2.50 2.75 3.00 3.25 3.50 3.75

0.2402 0.2123 0.1831 0.1563 0.1312 0.1085

4.00 4.25 4.50 4.75 5.00 5.25

0.0937 0.0798 0.0722 0.0672 0.0625 0.0584

5.50 5.75 6.00 6.25 6.50 6.75

0.0542 0.0500 0.0459 0.0426 0.0401 0.0376

7.00 7.25 7.50 7.75 8.00 8.25

0.0351 0.0326 0.0308 0.0291 0.0274 0.0257

8.50 8.75 9.00 9.25

0.0241 0.0224 0.0208 0.0191

Hours

Accumulated Depth (%)

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.00% 1.81% 5.10% 9.24% 14.32% 20.31% 26.87% 33.85% 40.90% 47.45% 53.45% 58.75% 63.33% 67.24% 70.51% 73.23% 75.57% 77.56% 79.37% 81.05% 82.61% 84.07% 85.42% 86.67% 87.82% 88.89% 89.89% 90.83% 91.71% 92.52% 93.29% 94.02% 94.70% 95.35% 95.95% 96.51% 97.03% 97.50%

0.00 2.16 3.92 4.94 6.05 7.15 7.82 8.32 8.41 7.80 7.16 6.33 5.46 4.66 3.91 3.23 2.79 2.38 2.15 2.00 1.86 1.74 1.62 1.49 1.37 1.27 1.20 1.12 1.05 0.97 0.92 0.87 0.82 0.77 0.72 0.67 0.62 0.57

0.00 3.12 5.65 7.13 8.73 10.32 11.29 12.00 12.14 11.26 10.33 9.13 7.87 6.72 5.64 4.67 4.03 3.43 3.11 2.89 2.69 2.51 2.33 2.15 1.97 1.83 1.73 1.62 1.51 1.40 1.32 1.25 1.18 1.11 1.04 0.96 0.89 0.82

0.00 3.78 6.86 8.66 10.60 12.53 13.70 14.57 14.74 13.67 12.54 11.08 9.56 8.16 6.85 5.67 4.89 4.17 3.77 3.51 3.27 3.05 2.83 2.61 2.39 2.23 2.09 1.96 1.83 1.70 1.61 1.52 1.43 1.34 1.26 1.17 1.08 1.00

0.00 4.60 8.35 10.53 12.90 15.24 16.67 17.73 17.93 16.63 15.25 13.48 11.63 9.92 8.33 6.89 5.95 5.07 4.59 4.27 3.97 3.71 3.44 3.18 2.91 2.71 2.55 2.39 2.23 2.07 1.95 1.85 1.74 1.64 1.53 1.42 1.32 1.21

0.00 5.19 9.42 11.88 14.54 17.18 18.80 19.99 20.22 18.75 17.20 15.20 13.11 11.19 9.40 7.77 6.71 5.71 5.17 4.82 4.48 4.18 3.88 3.58 3.28 3.05 2.87 2.69 2.51 2.34 2.20 2.08 1.96 1.84 1.72 1.61 1.49 1.37

0.00 5.81 10.55 13.30 16.29 19.25 21.05 22.39 22.64 21.00 19.26 17.03 14.69 12.53 10.53 8.70 7.52 6.40 5.79 5.39 5.02 4.68 4.35 4.01 3.68 3.42 3.22 3.02 2.82 2.62 2.47 2.33 2.20 2.07 1.93 1.80 1.66 1.53

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo Hours 9.50 9.75 10.00 10.25 10.50 10.75 11.00 11.25 11.50 11.75 12.00

mm/hr for 1mm of total precipitation 0.0174 0.0158 0.0141 0.0124 0.0107

Accumulated Depth (%)

97.94% 98.33% 98.68% 98.99% 99.26% 99.49% 99.68% 99.82% 99.92% 99.98% 100.00%

0.0091 0.0074 0.0057 0.0041 0.0024 0.0008 12-hour Precipitation Total (mm)

Sameng Inc.

City of Grande Prairie 2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.52 0.47 0.42 0.37 0.32 0.27 0.22 0.17 0.12 0.07 0.02 29.8

0.75 0.68 0.61 0.53 0.46 0.39 0.32 0.25 0.18 0.10 0.03 43.0

0.91 0.82 0.74 0.65 0.56 0.47 0.39 0.30 0.21 0.13 0.04 52.2

1.11 1.00 0.89 0.79 0.68 0.58 0.47 0.37 0.26 0.15 0.05 63.5

1.25 1.13 1.01 0.89 0.77 0.65 0.53 0.41 0.29 0.17 0.05 71.6

1.40 1.26 1.13 1.00 0.86 0.73 0.59 0.46 0.33 0.19 0.06 80.2

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 11: New City of Grande Prairie 12-Hour Huff (2nd quartile) Design Storm, in mm/hr

0.00 0.25 0.50 0.75

mm/hr for 1mm of total precipitation 0.0000 0.0092 0.0234 0.0326

1.00 1.25 1.50 1.75 2.00 2.25

0.0387 0.0447 0.0554 0.0679 0.0819 0.0985

2.50 2.75 3.00 3.25 3.50 3.75

0.1148 0.1279 0.1404 0.1515 0.1615 0.1711

4.00 4.25 4.50 4.75 5.00 5.25

0.1796 0.1878 0.1931 0.1973 0.1970 0.1887

5.50 5.75 6.00 6.25 6.50 6.75

0.1792 0.1602 0.1394 0.1227 0.1093 0.0969

7.00 7.25 7.50 7.75 8.00 8.25

0.0875 0.0783 0.0704 0.0629 0.0563 0.0513

8.50 8.75 9.00 9.25

0.0463 0.0420 0.0379 0.0342

Hours

Accumulated Depth (%)

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.00% 0.23% 0.81% 1.63% 2.60% 3.72% 5.10% 6.80% 8.84% 11.31% 14.17% 17.37% 20.88% 24.66% 28.70% 32.98% 37.47% 42.16% 46.99% 51.92% 56.84% 61.56% 66.04% 70.04% 73.53% 76.59% 79.33% 81.75% 83.93% 85.89% 87.65% 89.22% 90.63% 91.91% 93.07% 94.12% 95.07% 95.92%

0.00 0.27 0.70 0.97 1.15 1.33 1.65 2.02 2.44 2.94 3.42 3.81 4.18 4.51 4.81 5.10 5.35 5.60 5.76 5.88 5.87 5.62 5.34 4.77 4.15 3.66 3.26 2.89 2.61 2.33 2.10 1.87 1.68 1.53 1.38 1.25 1.13 1.02

0.00 0.39 1.01 1.40 1.66 1.92 2.38 2.92 3.52 4.24 4.93 5.50 6.04 6.51 6.94 7.36 7.72 8.08 8.30 8.48 8.47 8.12 7.70 6.89 5.99 5.27 4.70 4.17 3.76 3.37 3.03 2.70 2.42 2.20 1.99 1.81 1.63 1.47

0.00 0.48 1.22 1.70 2.02 2.34 2.89 3.54 4.27 5.14 5.99 6.68 7.33 7.91 8.43 8.93 9.37 9.80 10.08 10.30 10.28 9.85 9.35 8.36 7.28 6.40 5.71 5.06 4.57 4.09 3.67 3.28 2.94 2.68 2.42 2.19 1.98 1.78

0.00 0.58 1.49 2.07 2.46 2.84 3.52 4.31 5.20 6.25 7.29 8.12 8.91 9.62 10.26 10.87 11.40 11.92 12.26 12.53 12.51 11.99 11.38 10.17 8.85 7.79 6.94 6.15 5.55 4.97 4.47 3.99 3.57 3.25 2.94 2.67 2.41 2.17

0.00 0.66 1.68 2.34 2.77 3.20 3.96 4.86 5.86 7.05 8.22 9.16 10.05 10.85 11.56 12.25 12.86 13.45 13.83 14.13 14.10 13.51 12.83 11.47 9.98 8.78 7.83 6.94 6.26 5.61 5.04 4.50 4.03 3.67 3.32 3.01 2.71 2.45

0.00 0.74 1.88 2.62 3.10 3.59 4.44 5.44 6.57 7.90 9.20 10.26 11.26 12.15 12.95 13.73 14.40 15.06 15.49 15.82 15.80 15.14 14.37 12.85 11.18 9.84 8.77 7.77 7.01 6.28 5.64 5.04 4.51 4.11 3.72 3.37 3.04 2.74

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo Hours 9.50 9.75 10.00 10.25 10.50 10.75 11.00 11.25 11.50 11.75 12.00

mm/hr for 1mm of total precipitation 0.0308 0.0275 0.0242 0.0208 0.0175

Accumulated Depth (%)

96.69% 97.38% 97.98% 98.50% 98.94% 99.29% 99.57% 99.77% 99.90% 99.98% 100.00%

0.0142 0.0110 0.0081 0.0052 0.0030 0.0009 12-hour Precipitation Total (mm)

Sameng Inc.

City of Grande Prairie 2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.92 0.82 0.72 0.62 0.52 0.42 0.33 0.24 0.16 0.09 0.03 29.8

1.33 1.18 1.04 0.90 0.75 0.61 0.47 0.35 0.22 0.13 0.04 43.0

1.61 1.44 1.26 1.09 0.91 0.74 0.57 0.42 0.27 0.16 0.05 52.2

1.96 1.75 1.53 1.32 1.11 0.90 0.70 0.51 0.33 0.19 0.06 63.5

2.21 1.97 1.73 1.49 1.25 1.01 0.79 0.58 0.37 0.22 0.07 71.6

2.47 2.21 1.94 1.67 1.40 1.14 0.88 0.65 0.42 0.24 0.08 80.2

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 12: New City of Grande Prairie 24-Hour Huff (1st quartile) Design Storm, in mm/hr

0.00 0.25 0.50 0.75

mm/hr for 1mm of total precipitation 0.0000 0.0225 0.0500 0.0615

1.00 1.25 1.50 1.75 2.00 2.25

0.0700 0.0784 0.0875 0.0969 0.1063 0.1156

2.50 2.75 3.00 3.25 3.50 3.75

0.1244 0.1292 0.1333 0.1375 0.1417 0.1436

4.00 4.25 4.50 4.75 5.00 5.25

0.1388 0.1335 0.1283 0.1231 0.1171 0.1098

5.50 5.75 6.00 6.25 6.50 6.75

0.1025 0.0952 0.0879 0.0812 0.0750 0.0687

7.00 7.25 7.50 7.75 8.00 8.25

0.0625 0.0564 0.0522 0.0486 0.0451 0.0415

8.50 8.75 9.00 9.25

0.0383 0.0367 0.0355 0.0343

Hours

Accumulated Depth (%)

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.00% 0.56% 1.81% 3.35% 5.10% 7.06% 9.24% 11.66% 14.32% 17.21% 20.31% 23.54% 26.87% 30.31% 33.85% 37.44% 40.90% 44.24% 47.45% 50.52% 53.45% 56.19% 58.75% 61.13% 63.33% 65.36% 67.24% 68.95% 70.51% 71.92% 73.23% 74.44% 75.57% 76.61% 77.56% 78.48% 79.37% 80.22%

0.00 0.82 1.82 2.24 2.55 2.85 3.19 3.53 3.87 4.21 4.53 4.70 4.85 5.01 5.16 5.23 5.05 4.86 4.67 4.48 4.26 4.00 3.73 3.47 3.20 2.96 2.73 2.50 2.28 2.05 1.90 1.77 1.64 1.51 1.39 1.34 1.29 1.25

0.00 1.18 2.63 3.23 3.67 4.11 4.59 5.09 5.58 6.07 6.53 6.78 7.00 7.22 7.44 7.54 7.28 7.01 6.74 6.46 6.15 5.76 5.38 5.00 4.62 4.27 3.94 3.61 3.28 2.96 2.74 2.55 2.37 2.18 2.01 1.93 1.86 1.80

0.00 1.43 3.19 3.92 4.46 4.99 5.57 6.17 6.77 7.37 7.92 8.23 8.49 8.76 9.02 9.15 8.84 8.51 8.17 7.84 7.46 6.99 6.53 6.06 5.60 5.18 4.78 4.38 3.98 3.59 3.32 3.10 2.87 2.65 2.44 2.34 2.26 2.18

0.00 1.74 3.87 4.76 5.42 6.07 6.77 7.50 8.22 8.95 9.63 10.00 10.32 10.64 10.97 11.11 10.74 10.34 9.93 9.53 9.06 8.50 7.93 7.37 6.80 6.29 5.80 5.32 4.84 4.36 4.04 3.76 3.49 3.22 2.96 2.84 2.75 2.65

0.00 1.96 4.36 5.36 6.10 6.83 7.62 8.44 9.25 10.07 10.83 11.25 11.61 11.98 12.34 12.51 12.09 11.63 11.18 10.72 10.20 9.56 8.93 8.29 7.66 7.08 6.53 5.99 5.44 4.91 4.54 4.24 3.93 3.62 3.33 3.20 3.09 2.98

0.00 2.19 4.88 6.00 6.82 7.64 8.53 9.45 10.36 11.27 12.13 12.59 13.00 13.41 13.81 14.00 13.53 13.02 12.51 12.00 11.42 10.70 9.99 9.28 8.57 7.92 7.31 6.70 6.09 5.49 5.09 4.74 4.40 4.05 3.73 3.58 3.46 3.34

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

9.50 9.75 10.00 10.25 10.50

mm/hr for 1mm of total precipitation 0.0330 0.0318 0.0307 0.0297 0.0287

10.75 11.00 11.25 11.50 11.75 12.00

0.0276 0.0266 0.0255 0.0245 0.0235 0.0224

12.25 12.50 12.75 13.00 13.25 13.50

0.0216 0.0210 0.0204 0.0198 0.0191 0.0185

13.75 14.00 14.25 14.50 14.75 15.00

0.0179 0.0172 0.0166 0.0160 0.0156 0.0152

15.25 15.50 15.75 16.00 16.25 16.50

0.0148 0.0143 0.0139 0.0135 0.0131 0.0127

16.75 17.00 17.25 17.50 17.75 18.00

0.0122 0.0118 0.0114 0.0110 0.0106 0.0102

18.25 18.50 18.75 19.00 19.25 19.50

0.0098 0.0093 0.0089 0.0085 0.0081 0.0077

Hours

City of Grande Prairie

Accumulated Depth (%)

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

81.05% 81.84% 82.61% 83.35% 84.07% 84.76% 85.42% 86.06% 86.67% 87.26% 87.82% 88.36% 88.89% 89.40% 89.89% 90.37% 90.83% 91.28% 91.71% 92.12% 92.52% 92.91% 93.29% 93.66% 94.02% 94.37% 94.70% 95.03% 95.35% 95.65% 95.95% 96.23% 96.51% 96.77% 97.03% 97.27% 97.50% 97.73% 97.94% 98.14% 98.33%

1.20 1.16 1.12 1.08 1.04 1.01 0.97 0.93 0.89 0.85 0.82 0.79 0.76 0.74 0.72 0.70 0.67 0.65 0.63 0.61 0.58 0.57 0.55 0.54 0.52 0.51 0.49 0.48 0.46 0.45 0.43 0.42 0.40 0.39 0.37 0.35 0.34 0.32 0.31 0.29 0.28

1.73 1.67 1.61 1.56 1.51 1.45 1.40 1.34 1.29 1.23 1.18 1.14 1.10 1.07 1.04 1.00 0.97 0.94 0.91 0.87 0.84 0.82 0.80 0.77 0.75 0.73 0.71 0.69 0.66 0.64 0.62 0.60 0.58 0.56 0.53 0.51 0.49 0.47 0.45 0.42 0.40

2.10 2.03 1.96 1.89 1.83 1.76 1.69 1.63 1.56 1.49 1.43 1.38 1.34 1.30 1.26 1.22 1.18 1.14 1.10 1.06 1.02 0.99 0.97 0.94 0.91 0.89 0.86 0.83 0.81 0.78 0.75 0.73 0.70 0.67 0.65 0.62 0.59 0.57 0.54 0.51 0.49

2.55 2.46 2.38 2.30 2.22 2.14 2.06 1.98 1.90 1.82 1.74 1.67 1.63 1.58 1.53 1.48 1.43 1.38 1.34 1.29 1.24 1.21 1.17 1.14 1.11 1.08 1.04 1.01 0.98 0.95 0.92 0.88 0.85 0.82 0.79 0.75 0.72 0.69 0.66 0.63 0.59

2.87 2.77 2.68 2.59 2.50 2.41 2.32 2.22 2.13 2.04 1.95 1.88 1.83 1.77 1.72 1.67 1.61 1.56 1.50 1.45 1.40 1.36 1.32 1.28 1.25 1.21 1.18 1.14 1.10 1.07 1.03 0.99 0.96 0.92 0.89 0.85 0.81 0.78 0.74 0.70 0.67

3.22 3.10 3.00 2.90 2.80 2.69 2.59 2.49 2.39 2.29 2.19 2.11 2.05 1.99 1.93 1.86 1.80 1.74 1.68 1.62 1.56 1.52 1.48 1.44 1.40 1.36 1.32 1.28 1.23 1.19 1.15 1.11 1.07 1.03 0.99 0.95 0.91 0.87 0.83 0.79 0.75

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

19.75 20.00 20.25 20.50 20.75

mm/hr for 1mm of total precipitation 0.0072 0.0068 0.0064 0.0060 0.0056

21.00 21.25 21.50 21.75 22.00 22.25

0.0052 0.0048 0.0043 0.0039 0.0035 0.0031

22.50 22.75 23.00 23.25 23.50 23.75

0.0027 0.0023 0.0018 0.0014 0.0010 0.0006

Hours

24.00

Accumulated Depth (%)

98.51% 98.68% 98.84% 98.99% 99.13% 99.26% 99.38% 99.49% 99.59% 99.68% 99.75% 99.82% 99.88% 99.92% 99.96% 99.98% 100.00% 100.00%

0.0002 24-hour Precipitation Total (mm)

Sameng Inc.

City of Grande Prairie 2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.26 0.25 0.23 0.22 0.20 0.19 0.17 0.16 0.14 0.13 0.11 0.10 0.08 0.07 0.05 0.04 0.02 0.01 36.4

0.38 0.36 0.34 0.32 0.29 0.27 0.25 0.23 0.21 0.18 0.16 0.14 0.12 0.10 0.07 0.05 0.03 0.01 52.5

0.46 0.44 0.41 0.38 0.36 0.33 0.30 0.28 0.25 0.22 0.20 0.17 0.14 0.12 0.09 0.06 0.04 0.01 63.7

0.56 0.53 0.50 0.46 0.43 0.40 0.37 0.34 0.30 0.27 0.24 0.21 0.17 0.14 0.11 0.08 0.05 0.01 77.4

0.63 0.60 0.56 0.52 0.49 0.45 0.41 0.38 0.34 0.30 0.27 0.23 0.20 0.16 0.12 0.09 0.05 0.01 87.1

0.71 0.67 0.63 0.59 0.54 0.50 0.46 0.42 0.38 0.34 0.30 0.26 0.22 0.18 0.14 0.10 0.06 0.02 97.5

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Table 13: New City of Grande Prairie 24-Hour Huff (2nd quartile) Design Storm, in mm/hr

0.00 0.25 0.50 0.75

mm/hr for 1mm of total precipitation 0.0000 0.0025 0.0067 0.0104

1.00 1.25 1.50 1.75 2.00 2.25

0.0130 0.0155 0.0172 0.0186 0.0201 0.0215

2.50 2.75 3.00 3.25 3.50 3.75

0.0232 0.0261 0.0292 0.0324 0.0355 0.0389

4.00 4.25 4.50 4.75 5.00 5.25

0.0430 0.0472 0.0513 0.0555 0.0592 0.0624

5.50 5.75 6.00 6.25 6.50 6.75

0.0655 0.0686 0.0717 0.0745 0.0770 0.0795

7.00 7.25 7.50 7.75 8.00 8.25

0.0820 0.0845 0.0867 0.0887 0.0908 0.0929

8.50 8.75 9.00 9.25

0.0949 0.0960 0.0971 0.0981

Hours

Accumulated Depth (%)

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.00% 0.06% 0.23% 0.49% 0.81% 1.20% 1.63% 2.10% 2.60% 3.14% 3.72% 4.37% 5.10% 5.91% 6.80% 7.77% 8.84% 10.02% 11.31% 12.69% 14.17% 15.73% 17.37% 19.08% 20.88% 22.74% 24.66% 26.65% 28.70% 30.81% 32.98% 35.20% 37.47% 39.79% 42.16% 44.56% 46.99% 49.44%

0.00 0.09 0.24 0.38 0.47 0.56 0.62 0.68 0.73 0.78 0.84 0.95 1.06 1.18 1.29 1.42 1.57 1.72 1.87 2.02 2.16 2.27 2.38 2.50 2.61 2.71 2.80 2.89 2.98 3.08 3.15 3.23 3.31 3.38 3.45 3.50 3.53 3.57

0.00 0.13 0.35 0.55 0.68 0.81 0.90 0.98 1.05 1.13 1.22 1.37 1.54 1.70 1.86 2.04 2.26 2.48 2.69 2.91 3.11 3.27 3.44 3.60 3.77 3.91 4.04 4.17 4.30 4.44 4.55 4.66 4.77 4.88 4.98 5.04 5.10 5.15

0.00 0.16 0.42 0.66 0.83 0.98 1.09 1.19 1.28 1.37 1.48 1.66 1.86 2.06 2.26 2.48 2.74 3.00 3.27 3.54 3.77 3.97 4.17 4.37 4.57 4.75 4.90 5.06 5.22 5.38 5.52 5.65 5.79 5.92 6.04 6.12 6.18 6.25

0.00 0.19 0.52 0.81 1.01 1.20 1.33 1.44 1.55 1.67 1.80 2.02 2.26 2.51 2.75 3.01 3.33 3.65 3.97 4.30 4.59 4.83 5.07 5.31 5.55 5.77 5.96 6.15 6.35 6.54 6.71 6.87 7.03 7.19 7.34 7.43 7.51 7.59

0.00 0.22 0.58 0.91 1.13 1.35 1.50 1.62 1.75 1.88 2.02 2.28 2.55 2.82 3.09 3.39 3.75 4.11 4.47 4.83 5.16 5.43 5.71 5.98 6.25 6.49 6.71 6.92 7.14 7.36 7.55 7.73 7.91 8.09 8.26 8.37 8.46 8.55

0.00 0.24 0.65 1.02 1.27 1.51 1.67 1.82 1.96 2.10 2.26 2.55 2.85 3.16 3.46 3.79 4.19 4.60 5.00 5.41 5.78 6.08 6.39 6.69 7.00 7.26 7.51 7.75 7.99 8.24 8.45 8.65 8.86 9.06 9.25 9.36 9.47 9.57

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

9.50 9.75 10.00 10.25 10.50

mm/hr for 1mm of total precipitation 0.0992 0.0995 0.0975 0.0954 0.0933

10.75 11.00 11.25 11.50 11.75 12.00

0.0913 0.0879 0.0827 0.0775 0.0723 0.0671

12.25 12.50 12.75 13.00 13.25 13.50

0.0630 0.0597 0.0563 0.0530 0.0497 0.0472

13.75 14.00 14.25 14.50 14.75 15.00

0.0449 0.0426 0.0403 0.0380 0.0361 0.0343

15.25 15.50 15.75 16.00 16.25 16.50

0.0324 0.0305 0.0288 0.0275 0.0262 0.0250

16.75 17.00 17.25 17.50 17.75 18.00

0.0238 0.0226 0.0215 0.0205 0.0195 0.0184

18.25 18.50 18.75 19.00 19.25 19.50

0.0175 0.0167 0.0158 0.0150 0.0142 0.0133

Hours

City of Grande Prairie

Accumulated Depth (%)

2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

51.92% 54.41% 56.84% 59.23% 61.56% 63.84% 66.04% 68.11% 70.04% 71.85% 73.53% 75.10% 76.59% 78.00% 79.33% 80.57% 81.75% 82.87% 83.93% 84.94% 85.89% 86.79% 87.65% 88.46% 89.22% 89.94% 90.63% 91.29% 91.91% 92.50% 93.07% 93.61% 94.12% 94.61% 95.07% 95.50% 95.92% 96.32% 96.69% 97.04% 97.38%

3.61 3.62 3.55 3.47 3.40 3.32 3.20 3.01 2.82 2.63 2.44 2.29 2.17 2.05 1.93 1.81 1.72 1.63 1.55 1.47 1.39 1.31 1.25 1.18 1.11 1.05 1.00 0.96 0.91 0.86 0.82 0.78 0.75 0.71 0.67 0.64 0.61 0.58 0.55 0.52 0.49

5.21 5.22 5.12 5.01 4.90 4.79 4.62 4.34 4.07 3.80 3.52 3.31 3.13 2.96 2.78 2.61 2.48 2.36 2.24 2.12 2.00 1.90 1.80 1.70 1.60 1.51 1.44 1.38 1.31 1.25 1.19 1.13 1.08 1.02 0.97 0.92 0.87 0.83 0.79 0.74 0.70

6.32 6.34 6.21 6.08 5.95 5.81 5.60 5.27 4.94 4.60 4.27 4.01 3.80 3.59 3.38 3.17 3.00 2.86 2.71 2.57 2.42 2.30 2.18 2.06 1.94 1.83 1.75 1.67 1.59 1.51 1.44 1.37 1.31 1.24 1.17 1.11 1.06 1.01 0.96 0.90 0.85

7.68 7.70 7.55 7.39 7.22 7.06 6.80 6.40 6.00 5.60 5.19 4.88 4.62 4.36 4.10 3.85 3.65 3.47 3.30 3.12 2.95 2.80 2.65 2.51 2.36 2.23 2.13 2.03 1.94 1.84 1.75 1.67 1.59 1.51 1.43 1.35 1.29 1.23 1.16 1.10 1.03

8.64 8.66 8.49 8.31 8.13 7.95 7.66 7.20 6.75 6.30 5.84 5.49 5.20 4.91 4.62 4.33 4.11 3.91 3.71 3.51 3.31 3.15 2.98 2.82 2.66 2.51 2.40 2.29 2.18 2.07 1.97 1.88 1.79 1.69 1.60 1.52 1.45 1.38 1.31 1.23 1.16

9.67 9.70 9.51 9.30 9.10 8.90 8.57 8.06 7.56 7.05 6.54 6.14 5.82 5.49 5.17 4.85 4.60 4.38 4.15 3.93 3.71 3.52 3.34 3.16 2.97 2.81 2.68 2.56 2.44 2.32 2.20 2.10 2.00 1.90 1.80 1.71 1.62 1.54 1.46 1.38 1.30

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

19.75 20.00 20.25 20.50 20.75

mm/hr for 1mm of total precipitation 0.0125 0.0117 0.0108 0.0100 0.0092

21.00 21.25 21.50 21.75 22.00 22.25

0.0083 0.0075 0.0067 0.0059 0.0051 0.0044

22.50 22.75 23.00 23.25 23.50 23.75

0.0037 0.0029 0.0023 0.0018 0.0013 0.0007

Hours

24.00

Accumulated Depth (%)

97.69% 97.98% 98.25% 98.50% 98.73% 98.94% 99.13% 99.29% 99.44% 99.57% 99.68% 99.77% 99.84% 99.90% 99.95% 99.98% 99.99% 100.00%

0.0002 24-hour Precipitation Total (mm)

Sameng Inc.

City of Grande Prairie 2-yr

5-yr

10-yr

25-yr

50-yr

100-yr

0.46 0.42 0.39 0.36 0.33 0.30 0.27 0.24 0.21 0.19 0.16 0.13 0.11 0.08 0.06 0.05 0.03 0.01 36.4

0.66 0.61 0.57 0.53 0.48 0.44 0.39 0.35 0.31 0.27 0.23 0.19 0.15 0.12 0.09 0.07 0.04 0.01 52.5

0.80 0.74 0.69 0.64 0.58 0.53 0.48 0.42 0.37 0.33 0.28 0.23 0.19 0.15 0.11 0.08 0.05 0.01 63.7

0.97 0.90 0.84 0.77 0.71 0.64 0.58 0.52 0.45 0.40 0.34 0.28 0.23 0.18 0.14 0.10 0.06 0.02 77.4

1.09 1.02 0.94 0.87 0.80 0.73 0.65 0.58 0.51 0.45 0.38 0.32 0.26 0.20 0.15 0.11 0.06 0.02 87.1

1.22 1.14 1.06 0.98 0.89 0.81 0.73 0.65 0.57 0.50 0.43 0.36 0.29 0.22 0.17 0.12 0.07 0.02 97.5

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

1.3.6

City of Grande Prairie

Synthetic Design Rainfalls – Conclusions and Recommendations

The City of Grande Prairie currently uses three synthetic design rainfall events of various duration for design purposes of the drainage network. They are the 4-hour Chicago, the 12hour AES and the 24-hour SCS distributions. Our review found that all three of these design rainfalls underestimate the total rainfall volume compared to the current IDF curves. These three design rainfall distributions were updated according to the newly developed IDF curves. The following synthetic rainfall distributions are recommended for the evaluation and design of sewer pipes, the major drainage system, ponds and any other drainage elements in the City of Grande Prairie. • The 4-hour Chicago distribution, discretized at 5-minutes interval and the peak intensity averaged over 10 minutes, is recommended. This is in line with what the City currently uses. The City should use the newly created distribution tabulated in Table 6, which have higher peak intensities than the current distributions. This design rainfall often guides the design of sewer pipes, given its very intense peak rainfall. Since the Chicago distribution is based on the IDF curve, using a shorter duration Chicago distribution rainfall (e.g. 1-hour) will not be any more conservative than the 4hour distribution; it may actually be less conservative. • The 12-hour AES and/or Huff Distribution (1st and/or 2nd quartile), discretized at 15-minutes interval, are recommended. The 12-hour event may govern pond sizes. Although the AES distribution is not commonly used by other municipalities, it appears to be in line with the more well-known Huff distributions. Since it has a higher peak intensity than the Huff distributions, it is believed that the AES method is more conservative for design purposes. The City should use the newly created distributions tabulated in Table 8 (AES), Table 10 (Huff, 1st quartile) and Table 11 (Huff, 2nd quartile). Through modeling exercises, one or two of these distributions could be eliminated (the ones that are less conservative). Although many municipalities do not use a 12-hour rainfall distribution for modeling purposes, it is good practice to simulate the drainage system under that event as it may be more conservative than the 24-hour events. • The 24-hour Huff Distribution (1st and/or 2nd quartile), discretized at 15-minutes interval, are recommended. Most municipalities in Alberta use the 24-hour Huff distribution as part of their design standards, and our review of rainfall distribution suggests that it is an adequate distribution for the City of Grande Prairie. The 24-hour event would generally govern pond sizes. The City currently uses the 24-hour SCS distribution which is extremely intense and conservative (even more so than the Chicago distribution). The SCS method is not commonly used by municipalities, and are being abandoned by most of the U.S., as they are not representative of actual rainfalls. It is recommended that the City stops using the 24-hour SCS distribution for modeling purposes. If the City still wants to

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

model an extremely peaky rainfall distribution for a 24-hour duration, the 24-hour Chicago distribution, discretized at 15-minutes interval, is recommended and is more suitable. Same as for the IDF curves, the City should continue to monitor rainfall in and around the City, and update the design rainfalls as needed. Through computer modeling, the City may add or remove synthetic design rainfalls from their design standards.

Sameng Inc.

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Appendix A: Gumbel Distribution for Various Rainfall Stations

Sameng Inc.

A-1

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-1 - Beaverlodge CDA â&#x20AC;&#x201C; Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 54.4 81.1 98.7 10 min 40.8 61.2 74.8 15 min 32.7 48.3 58.6 30 min 20.5 28.6 33.9 1 hr 12.4 16.7 19.6 2 hr 7.6 9.8 11.3 6 hr 3.8 4.9 5.6 12 hr 2.5 3.3 3.9 24 hr 1.7 2.5 3.1

25-yr (4% POE)

50-yr (2% POE)

121.0 91.9 71.7 40.7 23.3 13.2 6.5 4.6 3.8

137.6 104.6 81.3 45.7 26.0 14.6 7.2 5.2 4.3

100-yr 1000-yr (1% POE) (0.1% POE)

154.0 117.2 90.9 50.7 28.6 16.0 7.9 5.7 4.8

208.3 158.9 122.6 67.2 37.5 20.6 10.1 7.4 6.5

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-2

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-2 – Beaverlodge - MSC – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 10 min 15 min 23.3 42.7 55.5 30 min 15.4 26.6 33.9 1 hr 10.7 16.1 19.7 2 hr 6.7 9.1 10.8 6 hr 3.4 4.4 5.1 12 hr 2.2 3.2 3.8 24 hr 1.5 2.1 2.5

25-yr (4% POE)

50-yr (2% POE)

71.7 43.2 24.2 12.9 5.9 4.6 3.0

83.7 50.2 27.6 14.4 6.6 5.2 3.3

100-yr 1000-yr (1% POE) (0.1% POE)

95.6 57.0 30.9 15.9 7.2 5.8 3.7

135.0 79.7 41.9 21.0 9.3 7.7 4.9

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-3

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-3 – Eaglesham - AARD – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 10 min 15 min 38.7 56.2 67.8 30 min 26.2 37.5 45.0 1 hr 14.9 20.8 24.7 2 hr 8.3 11.4 13.4 6 hr 3.7 4.6 5.3 12 hr 2.4 3.2 3.8 24 hr 1.4 1.9 2.3

25-yr (4% POE)

50-yr (2% POE)

82.5 54.4 29.6 16.0 6.1 4.4 2.7

93.4 61.4 33.3 17.9 6.7 4.9 3.0

100-yr 1000-yr (1% POE) (0.1% POE)

104.2 68.4 36.9 19.8 7.2 5.4 3.3

140.0 91.4 49.0 26.0 9.2 7.0 4.3

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-4

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-4 – Grande Prairie A – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 52.7 73.8 87.8 10 min 39.2 54.3 64.3 15 min 31.7 43.6 51.6 30 min 19.9 27.0 31.7 1 hr 12.2 16.2 18.9 2 hr 7.5 10.1 11.8 6 hr 3.9 5.5 6.5 12 hr 2.5 3.5 4.1 24 hr 1.6 2.3 2.8

25-yr (4% POE)

50-yr (2% POE)

105.4 77.0 61.6 37.7 22.3 13.9 7.8 5.0 3.4

118.5 86.4 69.0 42.1 24.8 15.5 8.7 5.6 3.9

100-yr 1000-yr (1% POE) (0.1% POE)

131.5 95.7 76.4 46.5 27.3 17.1 9.7 6.2 4.3

174.5 126.5 100.7 61.0 35.5 22.3 12.8 8.2 5.8

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-5

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-5 – La Glace - AARD – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 10 min 15 min 36.5 60.1 75.8 30 min 24.6 39.3 49.1 1 hr 14.5 22.0 26.9 2 hr 8.7 12.0 14.2 6 hr 3.9 4.9 5.5 12 hr 2.3 2.8 3.2 24 hr 1.5 1.8 2.1

25-yr (4% POE)

50-yr (2% POE)

95.5 61.5 33.1 17.0 6.3 3.6 2.4

110.2 70.7 37.7 19.0 6.9 3.9 2.6

100-yr 1000-yr (1% POE) (0.1% POE)

124.7 79.8 42.3 21.0 7.5 4.2 2.8

172.7 109.8 57.5 27.8 9.5 5.3 3.5

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-6

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-6 – Peoria – AARD – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 10 min 15 min 36.2 56.6 70.1 30 min 23.8 36.2 44.4 1 hr 13.5 21.0 26.0 2 hr 8.6 12.6 15.3 6 hr 3.9 5.0 5.7 12 hr 2.4 3.2 3.8 24 hr 1.5 2.1 2.4

25-yr (4% POE)

50-yr (2% POE)

87.1 54.8 32.3 18.6 6.6 4.5 2.9

99.7 62.4 36.9 21.1 7.3 5.0 3.3

100-yr 1000-yr (1% POE) (0.1% POE)

112.3 70.1 41.5 23.5 7.9 5.5 3.6

153.7 95.3 56.8 31.6 10.2 7.2 4.8

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-7

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-7 – Rycroft - AGCM – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 10 min 15 min 27.9 37.3 43.5 30 min 20.2 28.9 34.7 1 hr 13.4 19.4 23.3 2 hr 8.6 11.8 13.8 6 hr 4.1 5.3 6.2 12 hr 2.7 3.5 4.1 24 hr 1.8 2.4 2.8

25-yr (4% POE)

50-yr (2% POE)

51.3 42.0 28.3 16.4 7.3 4.8 3.3

57.1 47.4 32.0 18.4 8.1 5.3 3.6

100-yr 1000-yr (1% POE) (0.1% POE)

62.8 52.8 35.7 20.3 8.9 5.8 4.0

81.8 70.6 47.9 26.6 11.5 7.6 5.2

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-8

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-8 – Teepee Creek - AARD – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 10 min 15 min 29.1 38.3 44.4 30 min 21.0 29.3 34.8 1 hr 12.8 17.2 20.1 2 hr 7.4 9.3 10.6 6 hr 3.4 4.2 4.7 12 hr 2.3 3.1 3.6 24 hr 1.4 2.0 2.4

25-yr (4% POE)

50-yr (2% POE)

52.1 41.7 23.8 12.2 5.4 4.2 2.8

57.9 46.9 26.5 13.4 5.8 4.7 3.2

100-yr 1000-yr (1% POE) (0.1% POE)

63.5 52.0 29.2 14.5 6.3 5.1 3.5

82.3 68.9 38.1 18.4 7.9 6.6 4.6

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-9

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-9 – Watino – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 64.7 102.4 127.4 10 min 43.5 63.9 77.4 15 min 35.1 51.0 61.5 30 min 24.1 36.0 43.9 1 hr 14.5 22.0 26.9 2 hr 8.8 13.1 15.9 6 hr 4.0 5.4 6.3 12 hr 2.4 3.3 3.9 24 hr 1.5 2.2 2.6

25-yr (4% POE)

50-yr (2% POE)

159.0 94.5 74.8 53.8 33.1 19.5 7.5 4.7 3.2

182.4 107.2 84.7 61.2 37.7 22.2 8.4 5.2 3.6

100-yr 1000-yr (1% POE) (0.1% POE)

205.7 119.8 94.5 68.5 42.3 24.8 9.3 5.8 4.0

282.5 161.4 126.8 92.7 57.4 33.5 12.1 7.7 5.4

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-10

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-10 – All Nine Stations (Average) – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 57.9 89.4 110.3 10 min 41.1 59.9 72.4 15 min 32.5 48.7 59.4 30 min 21.5 31.8 38.5 1 hr 13.0 18.8 22.6 2 hr 8.0 11.1 13.1 6 hr 3.8 5.0 5.8 12 hr 2.4 3.3 3.8 24 hr 1.6 2.2 2.7

25-yr (4% POE)

50-yr (2% POE)

136.7 88.2 72.9 47.1 27.4 15.7 6.8 4.5 3.2

156.3 99.9 83.0 53.5 31.0 17.6 7.5 5.1 3.6

100-yr 1000-yr (1% POE) (0.1% POE)

175.7 111.5 92.9 59.8 34.6 19.5 8.3 5.6 4.0

240.0 149.9 125.9 80.7 46.3 25.8 10.7 7.3 5.4

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-11

1000

Storm Drainage Master Plan 2018 Design Rainfall Assessment Memo

City of Grande Prairie

Figure A-11 – All Nine Stations (Upper 95% Confidence Interval) – Gumbel Distribution 2-yr

5-yr

10-yr

Rainfall Intensity (mm/hr)

Duration (50% POE) (20% POE) (10% POE) 5 min 65.3 101.9 127.2 10 min 45.5 67.4 82.6 15 min 35.3 53.4 65.7 30 min 23.2 34.7 42.5 1 hr 14.0 20.4 24.8 2 hr 8.5 11.9 14.3 6 hr 4.0 5.3 6.3 12 hr 2.6 3.5 4.2 24 hr 1.7 2.4 2.9

25-yr (4% POE)

50-yr (2% POE)

159.5 101.9 81.4 52.5 30.4 17.3 7.4 5.0 3.5

183.5 116.3 93.2 59.9 34.6 19.5 8.3 5.6 4.0

100-yr 1000-yr (1% POE) (0.1% POE)

207.5 130.6 104.8 67.3 38.7 21.7 9.1 6.2 4.5

286.7 178.0 143.4 91.8 52.4 29.1 12.0 8.2 6.1

100

1000-yr 100-yr

50-yr 25-yr

10-yr 5-yr 2-yr 1 1

100

Rainfall Duration (minutes)

Sameng Inc.

A-12

1000

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Appendix B: Memo â&#x20AC;&#x201C; Flow and Rainfall Monitoring Memo (March 26, 2018)

Sameng Inc.

1500 Baker Centre, 10025-106 Street Edmonton, AB T5J 1G3 Phone: (780) 482-2557 Fax: (780) 482-2538 maxime.belanger@sameng.com www.sameng.com

March 26, 2018

Our File: 1293

City of Grande Prairie Engineering Services 1st Floor, 10205 98 Street Grande Prairie, AB T8V 2E7 Attention: Re:

Richard Sali Design & Environmental Supervisor

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

Dear Mr. Sali, As part of the Storm Drainage Master Plan work and further to discussions during the meeting of March 13, 2018, Sameng has identified locations for flow monitoring and rain gauge placement that will help collect some useful data to characterize the storm runoff characteristics. We propose that the 3 rain gauge locations used in the past be maintained. We have also identified 2 City facilities where additional rain gauges may be placed for long term data collection. The first location is at the maintenance building for Ivy lake, while the second is at the Eastlink Centre Knowledge Campus. We have identified a total of 6 locations for flow monitoring, to collect data that represent different types of landuse throughout the City. Hopefully, there will be sufficient rainfall this year to help with a comparison of model results versus the flow monitoring data. We have also identified 2 locations for water quality measurements coinciding with the flow monitoring locations. The first location is upstream of the Canfor Ditch, while the second is downstream of the highway commercial area at 116 Avenue. The attached memo provides a summary of past monitoring activities, and information of the proposed locations. Sincerely,

Nathan Forsyth, P.Eng. Municipal / Water Resources Engineer

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

City of Grande Prairie

1.0 Overview 1.1

Introduction

The following describes the recommended rainfall and flow monitoring program for the City of Grande Prairie (City). As part of the Storm Drainage Master Plan preparation, Sameng has reviewed the past monitoring activities and prepared recommendations for monitoring in 2018. The key purposes of monitoring rainfall and storm runoff flows are to provide a better understanding of the relationship between rainfall and runoff. This would then extend to provide information for calibrating the computer simulation models used to evaluate and design storm infrastructure in the City. A number of factors influence how runoff are derived from rainfall events. Having measured data to calibrate the computer models provides for improved confidence on system assessment results. 1.2

Rainfall Monitoring

The City uses electronic â&#x20AC;&#x2DC;tipping bucketâ&#x20AC;&#x2122; style rain gauges that can measure rainfall continuously. Data from these gauges was recorded at 1 minute intervals, and collected wirelessly by the City. Another weather station is operated by NAVCAN at the Grande Prairie Airport, measuring rainfall at 6-hour intervals, as well as other climate data such as wind speed and direction. Gauges measure rainfall at a single location, so multiple gauges, spaced throughout the City is necessary to determine the distribution of rainfall throughout the City. Alternatively, detailed rainfall distributions can be measured using a weather radar station. Environment Canada operates a weather radar stations, such as the one near Spirit River, to observe rainfall over wide areas. As this technology has improved in its operational simplicity and became economical, some municipalities have started operating their own stations for local observations with greater refinement. The City may consider future rainfall monitoring to include weather radar installations. 1.3

Flow Monitoring

The City uses Depth-Velocity sensors to measure flow rates in sewer pipes. These sensors, installed by SFE Global are used to directly measure the depth and velocity of flows in a pipe, and calculate flow rate based on the pipe geometry. Flow depth is measured by a submerged pressure transducer that measures the depth of water above the sensor. Velocity is measured by ultra-sonic doppler emitted from the sensor. The sensor is connected to a base located at a nearby manhole, near the access point, where it can continuously collect and transmit readings. Velocity, depth, and flowrate measurements are recorded separately at five-minute intervals. The raw data is collected wirelessly.

Sameng Inc.

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

1.4

City of Grande Prairie

Quality Assurance and Data Verification.

Rainfall and pipe flow measurements can provide valuable information for the operation and maintenance of stormwater drainage systems. Regular maintenance and inspection can help ensure the quality of the data collected. Tipping-bucket rain gauges are typically calibrated before installation, and are checked during installation and removal. Data from these gauges can be verified with a graduated cylinder gauge placed beside tipping bucket, checked manually at regular intervals. Flow monitors are calibrated prior to installation, and verified at installation and removal. Monitors should be checked regularly to ensure they remain clean and in place. They should also be verified regularly by manual measurements of depth. A staff gauge can be used to verify the high water mark recorded by the gauge. The City should consider implementing both rainfall and flow monitoring data verification procedures for all future monitoring activities. 1.5

Past and Current Monitoring

The City maintains 3 rain gauges, as shown on Figure 1. These stations are maintained from May to September each year and taken down for the winter. Two of the stations are located on the rooftops of Fire Halls, while the third is located on the roof to the City Operations building. The City maintained 3 flow monitors from 2009-2012, and 4 monitors from 2013. The location of these sensors is shown in Figure 1. A total of 7 locations have flow monitoring information, though three of these locations have only a single year of data recorded. The past flow record data is summarized in Table 1. Table 1: Past Flow Monitoring Locations

Location MH#

Location (Description)

Pipe Size (mm)

Years Active

54017

108 Street & 107 Avenue North of Hospital Near Ditch

1400

2017

97003

88 Street South of 116 Avenue

1000

2017

1200

2010-2017

57100 75001

92 Street South of 92 Avenue 109 Street & 89 Avenue 116 Avenue near Outfall

1650 1500

57299

97 Avenue & 114 Street

1050

63507

92 Avenue, East of 98A Street

550

2017 2009-2016 2009, 20112016 2009, 20132016

96006

Sameng Inc.

LEGEND

CR E

CITY BOUNDARY

PROPERTY LINE STORM PIPE (BASIN BY COLOUR) WATERCOURSE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE

132 AVENUE R BEA

CRYSTAL LAKE STORM FACILITY

INT

RAIN GAUGE AND FLOW MONITOR LEGEND

EEK CR

ROYAL OAKS NORTH

RAIN GAUGE

100 STREET

INT INT

INT

INT INT

INT

FLOW MONITOR RAIN GAUGE CATCHMENT DIVIDE

INT

CREE

INT

BEAR

WETLAND

INT

INT INT

INT

INT INT

2009-2016

CRYSTAL LAKE

INT

2017

INT

IN/OUTLET

INT IN/OUTLET

IN/OUTLET

INT INT

INT

116 AVENUE

INT

AR INT

CR INT

2017 RESERVOIR

10.97

12.19

WESTGATE EAST

IN/OUTLET

INT

BEAR

IVY LAKE

INT

100 AVENUE

INT

K CREE

HIGHWAY 43

2009, 2013-2016 500 CMP 1980 16.50 0.00

2017

2010-2017 INT

84 STREET

CREE K

92 STREET

BEAR

84 AVENUE

WOOD LAKE

Prepared By:

REE

INT

BEA

116 STREET

2009, 2011-2016

INT

108 STREET

INT

INT INT

BE INT

INT INT INT

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

INT

INT INT

Client:

INT INT

INT

INT INT

INT

PINNACLE LAKE

INT

FLYINGSHOT LAKE

CR E

INT INT

68 AVENUE

INT

BEAR CREEK

K CREE BEAR

Stormwater Master Plan 2017

INT

IN/OUTLET

RESOURCES ROAD

Project: O'BRIEN LAKE

INT

Title: BICKELL'S POND

Existing Monitoring Locations 2009 - 2017 Scale:

Figure:

1:40,000

LEGEND

CR E

CITY BOUNDARY

PROPERTY LINE STORM PIPE (BASIN BY COLOUR) WATERCOURSE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE

132 AVENUE R BEA

CRYSTAL LAKE STORM FACILITY

INT

EEK CR

ROYAL OAKS NORTH

RAIN GAUGE AND FLOW MONITOR LEGEND

100 STREET

INT INT

RG - GRANDE PRAIRIE FIRE DEPARTMENT SALMOND STATION

RAIN GAUGE FLOW MONITOR INT

INT

CREE

INT

BEAR

WETLAND

INT

RAIN GAUGE CATCHMENT DIVIDE

CRYSTAL LAKE

INT

IN/OUTLET

IN/OUTLET INT INT

INT INT

INT

116 AVENUE

INT

1 - MH 80004 INT

INT

CR INT

RESERVOIR

10.97

12.19

WESTGATE EAST

IN/OUTLET

INT

INT INT

INT

BEAR

IVY LAKE

INT

100 AVENUE

INT

CREE

HIGHWAY 43

RG - GRANDE PRAIRIE TRANSIT

6 - MH 57204

500 CMP 1980 16.50 0.00

2 - MH 63198 INT

5 - MH 57100

RG - GRANDE PRAIRIE FIRE DEPARTMENT EAGAR STATION

WOOD LAKE

Prepared By:

INT

RC REE K

INT

3 - MH 56136

84 STREET

84 AVENUE

92 STREET

CREE K

BEA

116 STREET

BEAR

INT

108 STREET

INT

INT INT

INT

BE INT

x2 x2

INT INT INT

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

INT

4 - MH 52003

Client:

INT

B INT

INT

PINNACLE LAKE

INT

EE BE

FLYINGSHOT LAKE

INT INT

68 AVENUE

INT

BEAR CREEK

K CREE BEAR

Stormwater Master Plan 2017

INT

IN/OUTLET

RESOURCES ROAD

Project: O'BRIEN LAKE

INT

Title: BICKELL'S POND

Proposed Monitoring Locations 2018 Scale:

Figure:

1:40,000

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

City of Grande Prairie

2.0 Monitoring Recommendations Sameng has considered where flow monitoring should be located in 2018 to aid in calibrating the integrated storm model used in developing the new Storm Drainage Master Plan. The recommended monitoring locations are shown in Figure 2. 2.1

Rainfall Monitors

The previous flow monitoring locations should be maintained, as they are well distributed for the City. An additional 2 locations are recommended to improve the quality of rainfall data for calibration purposes. These locations have been selected to maintain even spacing between gauges, and where City facilities exist. In selecting locations for this area of the City, we had discussed the potential for a location close to Crystal Lake. On further investigation however, the City facility building at Crystal Lake is close to trees that may impact the performance of the rain gauge. NEW RAIN GAUGE LOCATION A A new rain gauge is recommended on the maintenance shed north of Ivy Lake. This location will measure rainfall for the northeast corner of the City, and can be used to calibrate models for this area.

Figure 3: New Rain Gauge Location A

Sameng Inc.

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

City of Grande Prairie

NEW RAIN GAUGE LOCATION B To measure rainfall in the Southwest section of the City, a rain gauge is recommended on the roof of the City Facility at the Eastlink Centre, as shown in Figure 4.

Figure 4: New Rain Gauge Location B

POTENTIAL MONITORING AT GRANDE PRAIRIE AIRPORT A rain gauge is operated by NAVCAN at the Grande Prairie airport. Rainfall is recorded at six-hour intervals, which is less useful for calibrating purposes, but can be used to confirm total volumes of rainfall events. We have also discussed the potential for measuring continuous rainfall at the Grande Prairie Airport. Although this location is too distant from most of the City to be very useful for model calibration, it is useful in establishing general rainfall data, for the purposes of updating IDF curves.

Sameng Inc.

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

2.2

City of Grande Prairie

Flow Monitoring Locations

As requested by the City, we have identified 6 locations for measuring flows in 2018. These locations were selected based on the expected usefulness in calibrating the model, as well as to characterize the storm runoff characteristics of different land use types. NEW FLOW MONITORING LOCATION #1 A new flow monitor is recommended in the 2100mm diameter storm pipe on 116 Avenue, as shown on Figure 5. A monitor at this location will measure flows from the Highway Commercial Area north of 116 Avenue, around 101 Street and 102 Street. This location is also recommended for water quality monitoring. As there are no storage or water quality facilities between this location and the outfall, this will be a suitable location for measuring typical, unbuffered highway commercial development loading to the creek. Discrete monitoring would be preferable to measure how water quality varies throughout a runoff event, so that efficient improvements can be designed.

Figure 5: Flow Monitoring Location #1

Sameng Inc.

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

City of Grande Prairie

NEW FLOW MONITORING LOCATION #2 A number of locations were considered in monitoring flows in the central portion of the City. The area is complex due to the number of outfalls, and the interconnections between the various systems. The 750mm diameter storm pipe shown on Figure 6 was selected based on it being downstream of an area known to have flooding concerns.

Figure 6: Flow Monitoring Location #2

Sameng Inc.

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

City of Grande Prairie

NEW FLOW MONITORING LOCATION #3 Figure 7 shows the proposed location of a flow monitor in the 1050mm diameter storm pipe on 84 Avenue, outside the Grande Prairie Cemetery. The basin for this pipe is a recently completed residential area with a dry pond. This neighborhood is representative of new developments with a storm pond. As such, runoff and flow characteristics from this flow monitor will serve as a good proxy for new developments.

Figure 7: Flow Monitoring Location #3

Sameng Inc.

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

City of Grande Prairie

NEW FLOW MONITORING LOCATION #4 Monitoring flow in the 600mm diameter storm pipe shown in Figure 8 will allow calibration of a residential neighborhood that is characteristic of other established areas of the City. The basin of this pipe relies on long roadside gutters to collect runoff at catchbasins. As much of the travel distance for runoff is on the surface, the parameters used for runoff may be different than other residential areas. Monitoring in this area will allow differentiation in parameters for residential areas of this type.

Figure 8: Flow Monitoring Location #4

Sameng Inc.

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

City of Grande Prairie

NEW FLOW MONITORING LOCATION #5 & #6 In 2017, a flow monitor was installed on 89 Avenue at location #5, as shown in Figure 9. This monitor is being used to determine flow rates in the Canfor Ditch, located east across 108 Street. Continuing monitoring at this location is recommended to help determine the effectiveness of a new stormwater facility to be built in this area. Water quality should be measured at this location to provide measurements that capture a large commercial/industrial area, upstream of the CanFor ditch. In addition, a new flow monitoring location upstream in the same basin is recommended at Location #6, as shown in Figure 10.

Figure 9: Flow Monitoring Location #5

Sameng Inc.

Storm Drainage Master Plan 2018 Flow and Rainfall Monitoring Memo

City of Grande Prairie

Figure 10: Flow Monitoring Location #6

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Appendix C: Stormwater Management Facility Summary Sheets

Sameng Inc.

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Ivy Lake Estates

Facility Type

Wet Pond

Location

Northwest corner of 100 Avenue & 88 Street

Catchment Area

130 ha

Year of Construction

1980

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (Ivy Lake Estates, Crystal Heights) are fully developed.

Inlet / Outlet

Inlets: 675mm to the west (656.53m); 375mm to the southwest (657.70m); 1200mm to the northeast (655.88m); 450mm to the northeast (does it exists?) Outlets: 900mm reducing to 600mm to the southeast (655.20m), flowing towards Pond 27 (west cell)

Control Structure

NWL is controlled by invert of 380mm pipe just downstream of MH96205 (657.27m). Flow Rate is controlled by a 1m length 380mm diameter pipe constriction just downstream of MH96205, which is followed by a 600mm pipe. Others: A normally closed 200mm flow bypass (655.05m) with valve located at MH96205 allows the draining of the pond to the downstream storm sewers.

Overflow

Into Pond: From the northeast near 1200mm inlet. Out of Pond: Emergency Overflow to the northeast at 659.59m (from LiDAR) or 659.00m (from design drawings), overflowing to the 88 Street grassed corridor, south towards north ditch of 100 Avenue, and east into Pond 27 (west cell).

Comments

Design NWL (657.33m) is higher than pipe controlling NWL (657.27m).

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

659.00

1.67

115,000

Normal Water Level (NWL)

657.33

0.00

Pond Bottom

655.55

-1.78

Surface Overflow to Downstream

659.59

2.32

151,400

Building Flooding

659.14

1.87

117,500

100-year 24-hour

658.36

1.09

63,900

100-year 4-hour

658.03

0.76

43,200

5-year 4-hour

657.66

0.39

21,300

Normal Water Level (NWL)

657.27

0.00

Design

Modeled / LiDAR

659.5

Water Elevation (m)

659.0

658.5

658.0

657.5

657.0

20,000

40,000

60,000 80,000 Live Storage (m3)

100,000

120,000

140,000

Note: Stage-Storage Curve derived from LiDAR (collected in 2014).

Sameng Inc.

C-1

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Woodgrove

Facility Type

Dry Pond (controlled surge pond)

Location

East of 88 Street, south of 116 Avenue

Catchment Area

52 ha

Year of Construction

1993

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (Ivy Lake Estates, Crystal Heights) are fully developed.

Inlet / Outlet: 1000mm to the west (667.05m)

Inlet / Outlet

Flow Rate is controlled by smaller pipes downstream of the dry pond (1000mm pipe reduced to 700mm and 400mm downstream of pond). City documentation indicate the design flow to be 85 L/s.

Control Structure

Into Pond: None. Out of Pond: No defined Emergency Overflow. Overflow will likely be to the southeast of the pond over the berm that surrounds the pond, into the parking area, agricultural area and undeveloped natural area at an elevation of 670.11m (from LiDAR). Top of berm is at elevation of 670.00m according to the design drawings.

Overflow

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

669.55

2.50

14,250

Pond Bottom

667.05

0.00

Design

Modeled / LiDAR Building Flooding

No risk

N/A

Surface Overflow to Downstream

670.00

2.95

16,600

100-year 24-hour

669.78

2.73

14,000

100-year 4-hour

669.60

2.55

12,100

5-year 4-hour

668.83

1.78

5,200

Pond Bottom

667.05

0.00

670.5 670.0

Water Elevation (m)

669.5 669.0

668.5 668.0 667.5 667.0 666.5

2,000

4,000

6,000

8,000 10,000 Live Storage (m3)

12,000

14,000

16,000

18,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-2

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Country Club West

Facility Type

Dry Pond (controlled surge pond)

Location

63 Avenue & 99 Street

Catchment Area

33 ha

Year of Construction

1995

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (Country Club West) are fully developed.

Inlet / Outlet

Inlet / Outlet: 1050mm to the east (649.90m), flowing into a 375mm pipe after going through the control structure.

Control Structure

Flow Rate is controlled by an orifice at the 375mm outlet of MH 50190. The orifice size is unknown, but is estimated equivalent to a 172mm diameter orifice. The Country Club West Stormwater Design Report indicate the design flow to be 124 L/s.

Overflow

Into Pond: From the northeast at 63 Avenue, and from the easement east of the pond (near 1050mm inlet/outlet). Out of Pond: Emergency Overflow to the southwest via a culvert at an elevation of 652.87m (estimated from LiDAR, culvert diameter unknown) and into a ditch overflowing into Bear Creek. By overland, water will overflow at the same location and into the same ditch at an elevation of 653.59m (from LiDAR).

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

652.12

1.20

6,000

Pond Bottom

650.92

0.00

Building Flooding

No risk

N/A

Surface Overflow to Downstream

653.59

2.67

15,100

100-year 24-hour

653.37

2.45

13,000

100-year 4-hour

653.22

2.30

11,700

5-year 4-hour

652.24

1.32

4,300

Pond Bottom

650.92

0.00

Design

Water Elevation (m)

Modeled / LiDAR

653.6 653.4 653.2 653.0 652.8 652.6 652.4 652.2 652.0 651.8 651.6 651.4 651.2 651.0 650.8 650.6

2,000

4,000

6,000 8,000 Live Storage (m3)

10,000

12,000

14,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-3

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Mountview

Facility Type

Dry Pond (surge pond)

Location

112 Avenue and 97 Street

Catchment Area

65 ha

Year of Construction

Late 1990's

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (West end of Mountainview) are fully developed. Inlet / Outlet: 375mm pipe at south end of pond (assumed size and location) connecting to the 375mm pipe just east of the pond.

Inlet / Outlet

Flow Rate is uncontrolled.

Control Structure

Into Pond: From the northeast, east and southeast of pond. Out of Pond: No defined Emergency Overflow. Water will overflow to the west into a shallow ditch at an elevation of 666.49m, and will overflow the railroad tracks at an elevation of 666.70m (from LiDAR).

Overflow

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

6,800

Pond Bottom

100-year 24-hour

667.02

2.82

100-year 4-hour

666.98

2.78

Building Flooding

666.52

2.32

Surface Overflow to Downstream

666.49

2.29

4,400

5-year 4-hour

666.46

2.26

4,200

Bottom

664.20

0.00

Design

Modeled / LiDAR

666.8 666.6 666.4

Water Elevation (m)

666.2 666.0 665.8 665.6 665.4 665.2 665.0 664.8 664.6

664.4 664.2 664.0

500

1,000

1,500

2,000 2,500 3,000 Live Storage (m3)

3,500

4,000

4,500

5,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-4

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Richmond Industrial

Facility Type

Dry Pond (flow-through)

Location

78 Avenue @ 108A Street

Catchment Area

30 ha

Year of Construction

1997

City of Grande Prairie

The area draining to this pond (southeast corner of Richmond Industrial Park serviced by Neighbourhood Development Stage ditches, along 78 Avenue) appears fully developed, but has lots of open gravel/asphalt space.

Inlet / Outlet

Inlets: 500mm culvert to the west (north) (661.06m); 500mm culvert to the west (south) (660.89m); east ditch of 108A Street coming in on west side of pond; west ditch of 108 Street coming in at southeast end of pond. Outlets: 300mm pipe to the east of the pond (569.46m), connecting to an existing storm sewer pipe flowing north on 108 Street.

Control Structure

Flow Rate is controlled by outlet and downstream sewer capacity. Others: There is a sluice gate located downstream of the outlet. Its purpose is unknown.

Overflow

Into Pond: None. Out of Pond: Emergency Overflow to the northeast and into the west ditch of 108 Street at 661.08m (from LiDAR), flowing north.

Comments

Although categorized as a dry pond, there is water pooling at the bottom of this pond with wetland-type vegetation. Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

660.80

1.20

1,900

Pond Bottom

659.60

0.00

Design

Modeled / LiDAR Building Flooding

No risk

N/A

100-year 24-hour

661.45

1.65

100-year 4-hour

661.38

1.58

5-year 4-hour

661.14

1.34

Surface Overflow to Downstream

661.08

1.28

2,300

Bottom

659.80

0.00

661.2 661.0

Water Elevation (m)

660.8 660.6 660.4 660.2 660.0 659.8 659.6

500

1,000 1,500 Live Storage (m3)

2,000

2,500

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-5

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Crystal Ridge

Facility Type

Dry Pond (controlled surge pond)

Location

124 Avenue & 98 Street

Catchment Area

14 ha

Year of Construction

1997

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (northwest part of Crystal Ridge) are fully developed.

Inlet / Outlet

Inlet / Outlet: A catchbasin manhole is located at the east end of the pond (inv. 676.43m). A 300mm and 450mm pipe comes to that CBMH, and a 525mm pipe leaves that CBMH. The flow eventually reaches the control structure just downstream of the pond.

Control Structure

Flow Rate is controlled by an orifice at the 450mm outlet of MH 80246 (676.29m). The orifice size is unknown, but the design drawings indicate a control to 190 L/s. The estimated equivalent circular orifice diameter is 225mm. Into Pond: From the northwest (alley). Out of Pond: Emergency Overflow to the south into the adjacent Pond 10 at northeast at 679.46m (from LiDAR) or 679.65m (from design drawings). Water may also overflow the pond to the west into a shallow swale flowing south, east of the railroad at an elevation of 679.49m (from LiDAR).

Overflow

Works in combination with Pond 10.

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

679.65

1.20

1,200

Pond Bottom

678.45

0.00

Building Flooding

No risk

N/A

100-year 24-hour

679.64

1.19

100-year 4-hour

679.63

1.18

5-year 4-hour

679.57

1.12

Surface Overflow to Downstream

679.46

1.01

600

Bottom

678.45

0.00

Design

Modeled / LiDAR

679.6

Water Elevation (m)

679.4 679.2

679.0 678.8 678.6

678.4 678.2

100

200

300 400 Live Storage (m3)

500

600

700

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-6

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Royal Oaks

Facility Type

Dry Pond (controlled surge pond)

Location

108 Street & 117 Avenue

Catchment Area

65 ha

Year of Construction

1999

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (south half of Royal Oaks) are fully developed.

Inlet / Outlet

Inlets: 1200mm to the east (660.95m) Inlet/Outlets: A catchbasin manhole is located in the center of the pond. A 600mm comes to that CBMH from the east and a 600mm pipe leaves that CBMH flowing southwest.

Control Structure

Flow Rate is controlled by smaller pipes downstream of the dry pond (1200mm and 1000mm pipes coming into pond, 600mm pipe leaving the pond). Design drawings indicate the peak release rate to be 120 L/s. Others: A sluice gate is located at MH83002 in front of the 600mm pipe leaving the manhole to the south. Its purpose is unknown. It is assumed to be fully open. Into Pond: From the southeast corner. Out of Pond: Emergency Overflow 900mm pipe to the southwest of the pond (662.23m) overflowing directy into Bear Creek via pipe, followed by overflow of 108 Street at 664.16m (from LiDAR).

Overflow

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

662.29

1.56

16,822

Pond Bottom

660.73

0.00

Surface Overflow to Downstream

664.16

3.43

51,800

Building Flooding

663.99

3.26

48,300

100-year 24-hour

662.39

1.66

16,600

100-year 4-hour

662.30

1.57

15,100

5-year 4-hour

661.60

0.87

4,200

Bottom

660.73

0.00

Design

Modeled / LiDAR

664.5 664.0

Water Elevation (m)

663.5 663.0 662.5

662.0 661.5 661.0 660.5

10,000

20,000

30,000 Live Storage (m3)

40,000

50,000

60,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-7

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Countryside South

Facility Type

Wet Pond

Location

90 Street & 60 Avenue

Catchment Area

93 ha

Year of Construction

1996

City of Grande Prairie

The area flowing into this pond is still being developed (Countryside South (complete) and Neighbourhood Development Stage Summerside (development starting)). Inlets: 1200mm to the northwest (642.00m). Outlets: 900mm to the northeast (644.92m) flowing into a ditch and ultimately into Woody Creek. The ultimate outlet structure is to the southeast of the pond (not yet constructed).

Inlet / Outlet

NWL is currently controlled by invert of 900mm outlet pipe at north corner of pond (644.25m). Flow Rate is controlled by downstream pipe sizes, until a proper control structure is constructed at southeast corner of pond. Design drawings indicate the peak release rate to be 340 L/s. Into Pond: No well defined overflow yet. Out of Pond: Emergency Overflow to the northeast into the ditch and ultimately to Woody Creek.

Control Structure

Overflow

The pond is not yet complete; it is constructed in stages as development happens.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

645.35

1.15

56,500

Normal Water Level (NWL)

644.20

0.00

Pond Bottom

643.00

-1.20

Design

Modeled / LiDAR Building Flooding

N/A

Surface Overflow to Downstream

645.64

1.44

35,700

100-year 24-hour

645.02

0.82

16,600

100-year 4-hour

644.92

0.72

14,100

5-year 4-hour

644.60

0.40

7,800

Normal Water Level (NWL)

644.20

0.00

645.8 645.6 Water Elevation (m)

645.4 645.2 645.0 644.8 644.6 644.4 644.2 644.0

5,000

10,000

15,000 20,000 25,000 Live Storage (m3)

30,000

35,000

40,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-8

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Pinnacle Ridge

Facility Type

Wet Pond

Location

Between Pinnacle Lake Drive & 108 Street

Catchment Area

64 ha

Year of Construction

2004

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (east half of Pinnacle Ridge) are fully developed.

Inlet / Outlet

Inlets: 1200mm to the north (657.10m); 600mm to the southwest (657.30m). Outlets: 450mm to the southeast (657.60m), reducing to 375mm after the control structure.

Control Structure

NWL is controlled by Hydrovex and 375mm pipe invert elevation at MH 1040 (659.30m). Flow Rate is controlled by Hydrovex 250 VHV-2 U/S (Design H=1.5m, Design Q=82L/s) at downstream outlet of MH 1040.

Overflow

Into Pond: From the north near 1200mm inlet. Out of Pond: Emergency Overflow to the east to 108 Street ditch at 661.19m (from LiDAR) or 660.80m (from design drawings). Once in that ditch, water flow south along the west ditch of 108 Street.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

660.80

1.50

24,000

Normal Water Level (NWL)

659.30

0.00

Pond Bottom

657.30

-2.00

Building Flooding

No risk

N/A

Surface Overflow to Downstream

661.19

1.89

30,500

100-year 24-hour

661.07

1.77

28,200

100-year 4-hour

660.60

1.30

19,500

5-year 4-hour

659.93

0.63

8,400

Normal Water Level (NWL)

659.30

0.00

Design

Modeled / LiDAR

661.4 661.2

Water Elevation (m)

661.0 660.8 660.6 660.4 660.2 660.0 659.8 659.6 659.4 659.2

5,000

10,000

15,000 20,000 Live Storage (m3)

25,000

30,000

35,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-9

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Crystal Ridge

Facility Type

Dry Pond (controlled surge pond)

Location

West of 98 Street & 123 Avenue

Catchment Area

14 ha

Year of Construction

Between 1997 and 2005

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (northwest part of Crystal Ridge) are fully developed. Inlet / Outlet: A catchbasin manhole is located at the east end of the pond (inv. 676.40m). It is connected to the main 450mm storm sewer east of the pond via a 450mm pipe just upstream of the control structure.

Inlet / Outlet

Flow Rate is controlled by an orifice at the 450mm outlet of MH 80245 (676.07m). The orifice size is unknown, but the design drawings indicate a control to 206 L/s. The estimated equivalent circular orifice diameter is 230mm.

Control Structure

Into Pond: From the north (from pond 6). Out of Pond: Emergency Overflow to the south into a swale at 678.46m (from LiDAR) or 678.60m (from design drawings).

Overflow

Works in combination with Pond 6.

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

678.60

1.20

3,250

Pond Bottom

677.40

0.00

Building Flooding

No risk

N/A

100-year 24-hour

678.61

1.21

100-year 4-hour

678.60

1.20

Surface Overflow to Downstream

678.46

1.06

2,100

5-year 4-hour

678.11

0.71

900

Bottom

677.40

0.00

Design

Modeled / LiDAR

678.6

Water Elevation (m)

678.4 678.2 678.0 677.8 677.6 677.4 677.2

500

1,000 1,500 Live Storage (m3)

2,000

2,500

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-10

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

NE of Country Club Estates

Facility Type

Wetland

Location

Northeast of 68 Avenue & Resources Road

Catchment Area

13 ha

Year of Construction

1999

Neighbourhood Development Stage

City of Grande Prairie

Collects drainage from Resources Road from about 68 to 76 Avenue, as well as the undeveloped land between Resources Road and the railroad north of the pond. Inlets: 750mm to the northwest (652.76m); 375mm to the southwest (652.96m). There is also a large area from the north between Resources Road and the railroad flowing into that wetland area. Outlets: 450mm reducing to 300mm to the southwest (653.14m). A 600mm culvert is located as the southeast corner of the pond (653.20m).

Inlet / Outlet

NWL is controlled by outlet pipe invert (653.14m). Flow Rate is controlled by smaller pipes downstream of the wetland (down to 300mm diameter).

Control Structure

Overflow

Into Pond: None other than overland drainage from the north. Out of Pond: Overflow of the wetland at 654.31m (from LiDAR) will be to the southwest onto Resources Road and into the undeveloped land to the southeast of the intersection,

Comments

Information on this pond is very sparse and the above should be reviewed for accuracy. Pond may also act as surge pond. Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

653.80

0.90

8,067

Normal Water Level (NWL)

652.90

0.00

Pond Bottom

652.20

-0.70

Building Flooding

No risk

N/A

Surface Overflow to Downstream

654.31

1.17

37,600

100-year 24-hour

653.55

0.41

4,500

100-year 4-hour

653.52

0.38

3,900

5-year 4-hour

653.36

0.22

1,200

Normal Water Level (NWL)

653.14

0.00

Design

Modeled / LiDAR

654.4

654.2 Water Elevation (m)

654.0 653.8 653.6 653.4 653.2 653.0 652.8 652.6

5,000

10,000

15,000 20,000 25,000 Live Storage (m3)

30,000

35,000

40,000

Note: Stage Storage data from LiDAR (2014). Sameng Inc.

C-11

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

East of Patterson Place

Facility Type

Wet Pond

Location

East of Resources Road at 76 Avenue

Catchment Area

13 ha

Year of Construction

1999

Neighbourhood Development Stage

Collects drainage from Resources Road from about 76 to 84 Avenue, as well as the land between Resources Road and the railroad north of the pond.

Inlet / Outlet

Inlets: 525mm to the northwest from private site (654.00m); 600mm to the northwest from the east ditch of Resources Road (654.00m); 375mm to the southwest draining a few catchbasins (653.50m). Outlets: 500mm reducing to 450mm to the west (653.50m) onto 76 Avenue.

City of Grande Prairie

NWL is controlled by outlet pipe invert (653.50m). Flow Rate is controlled by downstream sewer system. Others: Sluice Gate in MH56269 (normally open)

Control Structure

Into Pond: None. Out of Pond: Overflow of the pond at 655.82m (from LiDAR) will be to the west onto Resources Road and then south, making its way into the undeveloped land east of Resources Road. Overflow at the southeast corner of the pond is also possible at 655.89m (from LiDAR) directly into the undeveloped land, flowing south to Pond 11.

Overflow

Pond may also act as surge pond.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

654.91

1.41

10,494

Normal Water Level (NWL)

653.50

0.00

Pond Bottom

653.00

-0.50

Building Flooding

No risk

N/A

Surface Overflow to Downstream

655.82

2.32

18,700

100-year 24-hour

654.94

1.44

9,500

100-year 4-hour

654.80

1.30

8,300

5-year 4-hour

654.19

0.69

3,400

Normal Water Level (NWL)

653.50

0.00

Design

Water Elevation (m)

Modeled / LiDAR

656.0 655.8 655.6 655.4 655.2 655.0 654.8 654.6 654.4 654.2 654.0 653.8 653.6 653.4 653.2

2,000

4,000

6,000

8,000 10,000 12,000 Live Storage (m 3)

14,000

16,000

18,000

20,000

Note: Stage Storage data from LiDAR (2014). Sameng Inc.

C-12

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Westgate

Facility Type

Wet Pond

Location

Northwest of 104 Avenue & 114 Street

Catchment Area

61 ha

Year of Construction

2008-2010

City of Grande Prairie

The area flowing into this pond is still being developed (Westgate - about 50% developed, Neighbourhood Development Stage mostly area northwest of pond is undeveloped). Inlets: 750mm to the northwest (656.19m); 1050mm to the southeast (655.84m). Inlet/Outlet: 1050mm the southeast (655.84m).

Inlet / Outlet

Control Structure

NWL is controlled by pipe invert at pond outlet (657.73m). Flow Rate is controlled by 170mm orifice in MH 20013. Others: The control structure at MH20013 also has an overflow weir (see below) and a sluice gate to allow draining of the pond to the downstream storm sewers. Into Pond: From the southeast near 1050mm inlet at 661.19m (from LiDAR). Out of Pond: There is an Emergency Overflow weir located at MH20013 set at elevation of 659.80m. The natural pond overflow is to the southeast of the pond at 661.19m (from LiDAR).

Overflow

The control structure (MH20013) information might be outdated.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

660.00

2.27

11,716

Normal Water Level (NWL)

657.73

0.00

Pond Bottom

655.89

-1.84

Building Flooding

661.48

3.75

Surface Overflow to Downstream

661.19

3.46

88,500

100-year 24-hour

659.50

1.77

38,000

100-year 4-hour

658.94

1.21

24,300

5-year 4-hour

658.31

0.58

10,600

Normal Water Level (NWL)

657.73

0.00

Design

Water Elevation (m)

Modeled / LiDAR

660.4 660.2 660.0 659.8 659.6 659.4 659.2 659.0 658.8 658.6 658.4 658.2 658.0 657.8 657.6

10,000

20,000

30,000 Live Storage (m3)

40,000

50,000

60,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-13

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Crystal Lake

Facility Type

Wetland / Lake (Natural)

Location

East of Lakeland Drive & South of Lakeshore Drive

Catchment Area

36.6 ha

Year of Construction

2000 - 2004

City of Grande Prairie

All areas draining to Crystal Lake (Lakeland, north of Crystal Lake Estates, Northeast of Neighbourhood Development Stage Crystal Ridge) are fully developed. Inlets: 600mm culvert cross Lakeland Dr and 750mm (681.45m) to the northwest; 750mm (681.45m), 525mm (681.37m), 750mm (681.42m), 525mm (681.41m) to the north; 300mm (681.80m) from Pond #16, and 300mm (681.76m) from Pond #17. Outlets: Box culvert (681.79m) to a 300mm pipe at northeast corner to 127 Ave.

Inlet / Outlet

Control Structure

NWL is 681.49 m based on yearly averaged ice level. HWL is controlled by invert of the box culvert at the outlet (681.79m). Flow Rate is controlled by the 2 of F51 inlet grate at the box culvert outlet structure (160 L/s by design). Into Pond: From adjacent land around the lake. Out of Pond: Overflow to the northeast at 682.17m (from LiDAR) overflowing to Lakeshore Dr and 127 Ave; Overflow to the south at 682.31m (from LiDAR) overflowing to Crystal Lake Dr and 92 St.

Overflow

Average yearly ice level - 681.49m; July 2012 water level - 681.68 m.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

681.79

0.11

107,000

Normal Water Level (NWL)

681.68

0.00

Pond Bottom

680.25

-1.43

Building Flooding

682.25

0.57

Surface Overflow to Downstream

682.17

0.49

26,000

100-year 24-hour

681.95

0.27

13,400

100-year 4-hour

681.87

0.19

9,200

5-year 4-hour

681.81

0.13

6,600

Normal Water Level (NWL)

681.68

0.00

Design

Modeled / LiDAR

Water Elevation (m)

682.2

682.0

681.8

681.6

5,000

10,000

15,000 Live Storage (m3)

20,000

25,000

30,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-14

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Fire Hall

Facility Type

Wet Pond (used for diving/training purposes)

Location

East of Resources Road and South of 84 Avenue

Catchment Area

N/A

Year of Construction

Unknown

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

Normal Water Level (NWL)

Pond Bottom

City of Grande Prairie

Neighbourhood Development Stage Fully developed.

Inlet / Outlet

No information available.

Control Structure

No information available.

Overflow

No information available.

Comments

Design

Modeled / LiDAR Building Flooding

No risk

100-year 4-hour

100-year 24-hour

Surface Overflow to Downstream

5-year 4-hour

Normal Water Level (NWL)

658.0

Water Elevation (m)

657.8 657.6 657.4 657.2 657.0 656.8

100

200

300

400 500 Live Storage (m3)

600

700

800

900

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-15

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Crystal Ridge

Facility Type

Forebay (Wet)

Location

East of Lakeland Drive, North of 121 Avenue

Catchment Area

12 ha

Year of Construction

1978

City of Grande Prairie

All areas draining to this forebay (Central east portion of Crystal Ridge) are fully Neighbourhood Development Stage developed. Inlets: 750mm to the west (681.98m) Outlets: 300mm to the east (681.88m), flowing through control structure and into Crystal Lake (Pond 14).

Inlet / Outlet

Control Structure

NWL is controlled by adjustable weir in MH 30225 (682.39m). Flow Rate is controlled by same weir, combined with diameter of outlet pipe (300mm).

Into Pond: From the west near 750mm inlet. Out of Pond: Emergency Overflow to the northeast at 682.96m (from LiDAR) or 683.00m (from design), overflowing into Crystal Lake (Pond 14).

Overflow Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

683.00

0.61

970

Normal Water Level (NWL)

682.39

0.00

Pond Bottom

681.88

-0.51

Building Flooding

No risk

N/A

100-year 24-hour

683.19

0.80

100-year 4-hour

683.19

0.80

5-year 4-hour

683.12

0.73

Surface Overflow to Downstream

682.96

0.57

600

Normal Water Level (NWL)

682.39

0.00

Design

Modeled / LiDAR

683.0

Water Elevation (m)

682.8 682.6 682.4 682.2 682.0 681.8

100

200

300 400 Live Storage (m3)

500

600

700

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-16

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Crystal Ridge

Facility Type

Forebay (Wet)

Location

East of Lakeland Drive, at 125 Avenue

Catchment Area

14 ha

Year of Construction

1979

City of Grande Prairie

All areas draining to this forebay (Central east portion of Crystal Ridge) are fully Neighbourhood Development Stage developed. Inlets: 750mm to the west (681.95m) Outlets: 300mm to the east (682.39m), flowing through control structure and into Crystal Lake (Pond 14).

Inlet / Outlet

NWL is controlled by adjustable weir in MH 30225 (682.39m). Flow Rate is controlled by same weir, combined with diameter of outlet pipe (300mm).

Control Structure

Overflow

Into Pond: From the west near 750mm inlet. Out of Pond: Emergency Overflow to the northeast at 682.86m (from LiDAR) or 682.39m (from design), overflowing into Crystal Lake (Pond 14).

Comments

An oil skimmer is located downstream of the control structure at the outfall with Pond 14.

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

683.00

0.61

Normal Water Level (NWL)

682.39

0.00

Pond Bottom

681.88

-0.51

Design

Modeled / LiDAR Building Flooding

No risk

N/A

100-year 24-hour

683.02

0.63

100-year 4-hour

683.02

0.63

5-year 4-hour

683.01

0.62

Surface Overflow to Downstream

682.86

0.47

200

Normal Water Level (NWL)

682.39

0.00

682.9

Water Elevation (m)

682.8 682.7 682.6 682.5 682.4 682.3

80 100 Live Storage (m3)

120

140

160

180

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-17

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

N/A

Facility Type

Wet Pond (recreational)

Location

Muskoseepi Park

Catchment Area

N/A

Year of Construction

Unknown

City of Grande Prairie

Neighbourhood Development Stage N/A Inlets: None. Overland drainage only. Outlets: 200mm to the west and into Bear Creek.

Inlet / Outlet

Control Structure

Outlet is teed with a valve so that pond can be drained.

Into Pond: From the west near 750mm inlet. Out of Pond: Emergency Overflow to the northwest at 649.02m (from LiDAR), overflowing into Bear Creek.

Overflow

This pond was not designed for stormwater rentention purposes. It is recreational and fed by water mains.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

648.50

0.00

Normal Water Level (NWL)

648.50

0.00

Pond Bottom

646.50

-2.00

Design

Modeled / LiDAR Building Flooding

No risk

N/A

Surface Overflow to Downstream

649.02

0.52

2,400

100-year 4-hour

648.50

0.00

100-year 24-hour

648.50

0.00

5-year 4-hour

648.50

0.00

Normal Water Level (NWL)

648.50

0.00

649.1

Water Elevation (m)

649.0 648.9 648.8

648.7 648.6 648.5 648.4

500

1,000

1,500 Live Storage (m3)

2,000

2,500

3,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-18

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Mission Heights

Facility Type

Dry Pond (controlled surge pond)

Location

Community Knowledge Campus Kateri Drive & 68 Avenue

Catchment Area

60 ha

Year of Construction

Late 1990's

Neighbourhood Development Stage

Inlet / Outlet

City of Grande Prairie

All areas draining to this pond (South end of Mission Heights) are developed, with the exception of a site northwest of 68 Avenue and Kateri Drive. Inlets: 300mm to the west (651.59m); 375mm to the southwest (651.07m). Inlet/Outlets: 1500mm to the southeast (650.35m).

Control Structure

Flow Rate is controlled by orifices in MH25087: a 250mm diameter orifice at 649.70m and a 540mm diameter orifice at 651.32m.

Overflow

Into Pond: From the northeast near 1200mm inlet. Out of Pond: Emergency Overflow weir located in MH25087 at 651.90m. Natural overflow of the pond is to the southeast near the 1500mm inlet/outlet pipe at 653.93m (from LiDAR).

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

651.72

1.41

11,800

Pond Bottom

650.31

0.00

Building Flooding

No risk

N/A

Surface Overflow to Downstream

653.59

3.28

67,800

100-year 24-hour

652.04

1.73

20,000

100-year 4-hour

651.95

1.64

17,700

5-year 4-hour

651.34

1.03

5,800

Bottom

650.31

0.00

Design

Water Elevation (m)

Modeled / LiDAR

653.6 653.4 653.2 653.0 652.8 652.6 652.4 652.2 652.0 651.8 651.6 651.4 651.2 651.0 650.8 650.6 650.4 650.2 650.0

10,000

20,000

30,000 40,000 Live Storage (m3)

50,000

60,000

70,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-19

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Crystal Lake Estates

Facility Type

Wet Pond

Location

Southwest of 88 Street & 132 Avenue

Catchment Area

36 ha

Year of Construction

2003

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (north end of Crystal Lake Estates) are fully developed.

Inlet / Outlet

Control Structure

Inlets: 750mm to the south (673.50m); 300mm to the west (673.50m). Outlets: 525mm to the northeast (673.50m)

NWL is controlled by invert of 525mm pipe at downstream end of MH6001 (675.30m). Flow Rate is controlled by semi-circle orifice at 525mm outlet pipe in MH6001 (Design Q=179L/s at 1.2m Head). Into Pond: From the northeast near 1200mm inlet. Out of Pond: Emergency Overflow to the east and overtopping 88 Street at elevation of 677.20m (from LiDAR).

Overflow Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

676.50

1.20

18,300

Normal Water Level (NWL)

675.30

0.00

Pond Bottom

673.30

-2.00

Building Flooding

No risk

N/A

Surface Overflow to Downstream

677.20

1.90

28,900

100-year 24-hour

677.17

1.87

28,300

100-year 4-hour

676.47

1.17

15,900

5-year 4-hour

675.80

0.50

6,000

Normal Water Level (NWL)

675.30

0.00

Design

Modeled / LiDAR

677.4 677.2

Water Elevation (m)

677.0 676.8 676.6 676.4

676.2 676.0 675.8 675.6 675.4 675.2

5,000

10,000

15,000 20,000 Live Storage (m3)

25,000

30,000

35,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-20

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Country Club West

Facility Type

Dry Pond (controlled surge pond)

Location

South of 68 Avenue & West of 100 Street

Catchment Area

6 ha

Year of Construction

1999

City of Grande Prairie

All areas draining to this pond (Southwest corner of South Patterson Place) are fully Neighbourhood Development Stage developed. Inlets: 600mm to the northeast (651.10m); Outlets: 300mm to the west (650.82m).

Inlet / Outlet

Flow Rate is controlled by smaller pipes downstream of the dry pond (600mm pipe coming into pond, 300mm pipe leaving the pond).

Control Structure

Into Pond: No defined overflow to the pond. Out of Pond: No defined Emergency Overflow. Water will overflow to the west at 654.03m (from LiDAR) or to a ditch at the southwest corner at 654.15m (from LiDAR).

Overflow

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

651.60

0.78

Pond Bottom

650.82

0.00

Building Flooding

No risk

N/A

Surface Overflow to Downstream

654.03

3.21

5,500

100-year 24-hour

652.85

2.03

2,400

100-year 4-hour

652.73

1.91

2,100

5-year 4-hour

651.74

0.92

500

Bottom

650.82

0.00

Design

Modeled / LiDAR

654.0

Water Elevation (m)

653.5 653.0 652.5 652.0 651.5 651.0 650.5

500

1,000

1,500

2,000 2,500 Live Storage (m3)

3,000

3,500

4,000

4,500

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-21

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Westpointe

Facility Type

Dry Pond (controlled surge pond)

Location

South of 84 Avenue & East of 113 Street

Catchment Area

80 ha

Year of Construction

2002 - 2005

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (Westpointe) are fully developed. Inlets: 1400mm to the west (659.83m); 600mm to the southeast (660.60m) Outlets: 450mm to the north (659.41m), flowing into 1050mm pipe along 84 Ave

Inlet / Outlet

Control Structure

Flow Rate is controlled by Hydrovex 250 SVHV-2 (Design H=3.81m, Design Q=140L/s, Invert 659.39m) at downstream of MH 1031.

Overflow

Into Pond: From the west near 1400mm inlet; from southeast near 600mm inlet. Out of Pond: Emergency Overflow to the north at 663.29m (from LiDAR), overflowing to 84 Ave.

Comments

Pond was not dry in 2011; drains really slow and a lot of siltation was observed in 2012. LiDAR suggetes bottome of pond is highter than design. Storage volume is only 15,720 m 3 according to LiDAR. Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

662.90

1.50

31,090

Pond Bottom

661.40

0.00

Building Flooding

No risk

N/A

100-year 24-hour

663.39

1.99

Surface Overflow to Downstream

663.29

1.89

25,600

100-year 4-hour

663.13

1.73

21,900

5-year 4-hour

662.53

1.13

9,400

Bottom

661.40

0.00

Design

Modeled / LiDAR

663.4 663.2

Water Elevation (m)

663.0 662.8 662.6 662.4 662.2 662.0 661.8 661.6 661.4 661.2

5,000

10,000

15,000 Live Storage (m3)

20,000

25,000

30,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-22

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Westgate

Facility Type

Dry Pond (controlled surge pond)

Location

101 Avenue & 118 Street

Catchment Area

120 ha

Year of Construction

2010

City of Grande Prairie

Development in Westgate, west of 116 Street is at its early stages with many Neighbourhood Development Stage undeveloped sites. Bruchu Industrial, which is serviced by a ditches and culverts drainage system and is mostly developed, also flows into this stormwater management facility. Inlet/Outlets: 1050mm pipe to the southwest (660.24m); 1050mm pipe to the east (660.00m); 1050mm pipe to the southeast (659.90m).

Inlet / Outlet

Control Structure

Flow Rate is controlled by 180mm diameter orifice plate installed in MH1001, at invert of 658.65m. This manhole is a CBMH at the southwest corner of 116 Street and 101 Avenue. Others: A slide gate (with integrated orifice) is installed in MH1001 to lift the orifice away from the outlet pipe.

Overflow

Into Pond: From the southwest near 1050mm inlet/outlet pipe; from the east near 1050mm inlet/outlet pipe; from the southeast near the 1050mm inlet/outlet pipe; from the northeast (appears temporary to drain the undeveloped sites). Out of Pond: Emergency Overflow to the southeast onto 101 Avenue at 663.52m (from LiDAR).

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

663.00

3.08

38,900

Pond Bottom

659.92

0.00

Building Flooding

No risk

N/A

100-year 24-hour

663.65

3.45

Surface Overflow to Downstream

663.52

3.32

81,100

100-year 4-hour

662.96

2.76

57,600

5-year 4-hour

662.03

1.83

22,300

Bottom

660.20

0.00

Design

Modeled / LiDAR

664.0 663.5 663.0 Water Elevation (m)

662.5 662.0 661.5 661.0 660.5 660.0 659.5 659.0 658.5 658.0

10,000

20,000

30,000 40,000 50,000 Live Storage (m3)

60,000

70,000

80,000

Note: Stage Storage data from LiDAR (2014). Sameng Inc.

C-23

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Northridge

Facility Type

Dry Pond (controlled surge pond)

Location

South of 121 Avenue at 103 Street

Catchment Area

55 ha

Year of Construction

2006

Neighbourhood Development Stage

Majority of areas draining to this pond (west part of North Ridge) are fully developed. The northern part of that area (between 126 Avenue and 132 Avenue) is still being developed.

Inlet / Outlet

Inlet/Outlets: 1 CBMH in west pond connecting to a 300mm pipe; 5 CBMH in east pond connecting to a 300mm pipe (4 of them) and a 900mm pipe (1 of them).

Control Structure

Flow Rate is controlled by Hydrovex 350 SVHV-2 (Design H=3.09m, Design Q=288L/s) at downstream outlet of MH 577784, at invert of 661.97m.

City of Grande Prairie

Into Pond: From the northwest between the two ponds (from cul-de-sac); from the southeast (through walkway). Out of Pond: Emergency Overflow to the south through private property (grassed area) at 665.40m (from LiDAR) or 665.50m (from design drawings). Overflow between west and east cell is at 665.32m, at south end of ponds.

Overflow

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

664.90 / 665.32

1.05

19,000

663.85

0.00

Building Flooding

No risk

N/A

Surface Overflow to Downstream

665.40

1.30

16,200

100-year 24-hour

665.17

1.07

9,700

100-year 4-hour

664.62

0.52

900

5-year 4-hour

664.51

0.41

400

664.10 (west) 663.85 (East)

0.00

Design High Water Level (HWL) Pond Bottom Modeled / LiDAR

Bottom 665.6 665.4

Water Elevation (m)

665.2 665.0 664.8 664.6 664.4 664.2 664.0

663.8 663.6 663.4

2,000

4,000

6,000

8,000 10,000 Live Storage (m3)

12,000

14,000

16,000

18,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-24

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Oâ&#x20AC;&#x2122;Brien Lake

Facility Type

Wet Pond (Natural)

Location

West of 108 Street & South of 65 Avenue

Catchment Area

50 ha

Year of Construction

2005

City of Grande Prairie

All areas draining to this pond (Northeast of O'Brien Lake, East of Pinnacle Ridge) are Neighbourhood Development Stage fully developed. Inlets: 600mm to the northwest (652.40m); 750mm to the northeast (652.20m); Ditch to the northeast corner from Pond #9 (654.05m from LiDAR). Outlets: Sheet Pile Compound Weir to two culverts crossing 112 St at the southwest corner, following north to a ditch.

Inlet / Outlet

Control Structure

NWL is controlled by sheet pile weir (652.40m). Flow Rate is controlled by a 5m wide sheet pile weir at the southwest corner with a notch of 0.39m width and Q = 162 L/s. Into Pond: From the north near the 750mm inlet, from north at 111 St; from northwest near the 600mm inlet, from southwest near the weir. Out of Pond: Emergency Overflow to the west at the top of the weir (652.90m).

Overflow

Pond live storage volume is less than design volume based on LiDAR (32,390 m 3).

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

652.76

0.36

36,579

Normal Water Level (NWL)

652.40

0.00

Design

Pond Bottom Modeled / LiDAR Building Flooding

No risk

N/A

Surface Overflow to Downstream

652.90

0.50

42,300

100-year 24-hour

652.71

0.31

23,900

100-year 4-hour

652.65

0.25

18,900

5-year 4-hour

652.51

0.11

8,000

Normal Water Level (NWL)

652.40

0.00

653.6

Water Elevation (m)

653.4

653.2 653.0 652.8 652.6 652.4 652.2

20,000

40,000

60,000 Live Storage (m3)

80,000

100,000

120,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-25

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Pinnacle Ridge

Facility Type

Wet Pond

Location

East of 116 Street & North of 68 Avenue

Catchment Area

43 ha

Year of Construction

2006

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (West Pinnacle Ridge) are fully developed. Inlets: 450mm to the northwest (658.65m); 375mm to the north (658.88m); 750mm to the east (658.70m). Outlets: 525mm to the southwest (650.50m), flowing to the south through a culvert.

Inlet / Outlet

Control Structure

NWL is controlled by invert of 525mm outlet pipe (660.50m). Flow Rate is controlled by Hydrovex 350-VHV-2 (Design H=2.0m, Design Q=201L/s, Invert 660.00m) Into Pond: From the north near 375mm inlet; from east near 750mm inlet. Out of Pond: Emergency Overflow via a swale to the west at 662.04 m (from LiDAR) or 662.00m (from design drawings), overflowing to the road side ditch along 116 St.

Overflow

Live storage volume is higher than the design from LiDAR (14,000 m 3).

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

662.00

1.50

13,400

Normal Water Level (NWL)

660.50

0.00

Pond Bottom

658.50

-2.00

Design

Modeled / LiDAR Building Flooding

No risk

N/A

Surface Overflow to Downstream

662.04

1.54

14,500

100-year 24-hour

662.03

1.53

14,400

100-year 4-hour

661.84

1.34

12,300

5-year 4-hour

661.11

0.61

5,100

Normal Water Level (NWL)

660.50

0.00

662.2

662.0 Water Elevation (m)

661.8 661.6 661.4 661.2

661.0 660.8 660.6 660.4

2,000

4,000

6,000

8,000 10,000 Live Storage (m3)

12,000

14,000

16,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-26

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Crystal Landing

Facility Type

Wetland

Location

South of 100 Avenue & East of 87 Street

Catchment Area

45 ha (direct)

Year of Construction

2005

City of Grande Prairie

Most areas draining to this pond (West of Crystal Landing and Trumpeter Village) are fully Neighbourhood Development Stage developed as per 2016 air photo. Inlets: 450mm (652.80m) and 750mm (652.80m) to the northwest; 1050mm (652.80m) and 900mm (652.80m) to the northeast; 750mm to the southwest (654.30m) from Pond #1. Outlets: 2x900mm to the south (653.87m) from the eastern pond.

Inlet / Outlet

Control Structure

NWL is controlled by invert of orifice plate inside of MH downstream of the 2x900mm outlet pipes (654.30m). Flow Rate is controlled by a 0.95mx0.40m oriface plate with invert of 654.30m inside the MH downstream of the outlets.

Overflow

Into Pond: From the southwest near 750mm inlet; from the northwest near 450mm inlet; from northeast near 1050mm inlet. Out of Pond: Emergency Overflow to the south at 655.38m through a weir across the outlet MH (width 2.44m). 2 Parts to Pond, West Side and East Side, West side Drains to East.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

655.38

1.08

26,490

Normal Water Level (NWL)

654.30

0.00

Pond Bottom

652.30

-2.00

N/A

Surface Overflow to Downstream

655.31

1.01

24,600

100-year 24-hour

655.29

0.99

23,900

100-year 4-hour

655.15

0.85

19,800

5-year 4-hour

654.79

0.49

10,300

Normal Water Level (NWL)

654.30

0.00

Design

Modeled / LiDAR Building Flooding

655.6

Water Elevation (m)

655.4 655.2 655.0 654.8 654.6 654.4 654.2

5,000

10,000

15,000 Live Storage (m3)

20,000

25,000

30,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-27

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Signature Falls

Facility Type

Wet Pond / Conveyance Channel

Location

West of Range Road 55 & Norh of 68 Avenue

Catchment Area

75 ha

Year of Construction

2007

City of Grande Prairie

Areas draining to this pond in Countryside North are fully developed. The southwest part Neighbourhood Development Stage of Signature Falls is still being developed as per 2016 air photo. Inlet / Outlet

Control Structure

Inlets: 2x1500mm culvert to the west end (648.75m); 900mm to the west end (648.48m); ditch inlet to the north from Pond #60; 600mm (648.00m) and 300mm (648.00m) to the southwest; 600mm (646.20m) to the south end. Outlets: 3x1800mm culvert to the south (648.00m) to downstream ditch. NWL is controlled by invert of outlet culverts (648.00m). Flow Rate is controlled by the size of the outlet culverts. Into Pond: From the west end near 900mm inlet; from the north and southwest near 600mm inlet; from east of Range Road 55. Out of Pond: To the south at 650.65m (from LiDAR) near 3x1800 mm outlets across 68 Ave to downstream ditch.

Overflow

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

649.60

1.60

36,700

Normal Water Level (NWL)

648.00

0.00

Pond Bottom

646.00

-2.00

Design

Modeled / LiDAR Building Flooding

No risk

N/A

Surface Overflow to Downstream

650.65

2.65

53,800

100-year 24-hour

650.40

2.40

53,700

100-year 4-hour

650.27

2.27

53,700

5-year 4-hour

649.56

1.56

35,300

Normal Water Level (NWL)

648.00

0.00

650.2 650.0

Water Elevation (m)

649.8

649.6 649.4 649.2 649.0 648.8 648.6 648.4 648.2 648.0 647.8

10,000

20,000

30,000 Live Storage (m3)

40,000

50,000

60,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-28

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Signature Falls

Facility Type

Wet Pond

Location

North of 68 Avenue & West of 86 Street

Catchment Area

40 ha

Year of Construction

2006/2007

City of Grande Prairie

Neighbourhood Development Stage All areas draining to this pond (South of Signature Falls) are fully developed. Inlets: 750mm to the southwest (647.09m); 750mm to the northeast (647.10m). Outlets: 600mm to the southeast (647.20m).

Inlet / Outlet

Control Structure

NWL is controlled by invert of 600mm pipe at MH23182 (649.00m). Flow Rate is controlled the size of 600mm outlet pipe.

Overflow

Into Pond: From the east near 750mm inlet. Out of Pond: Emergency Overflow to the east at 651.92m to 86 St.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

650.50

1.50

9,700

Normal Water Level (NWL)

649.00

0.00

Pond Bottom

647.00

-2.00

Surface Overflow to Downstream

651.92

2.92

Building Flooding

651.78

2.78

22,200

100-year 24-hour

650.90

1.90

13,000

100-year 4-hour

650.61

1.61

10,600

5-year 4-hour

649.64

0.64

3,600

Normal Water Level (NWL)

649.00

0.00

Design

Water Elevation (m)

Modeled / LiDAR

652.2 652.0 651.8 651.6 651.4 651.2 651.0 650.8 650.6 650.4 650.2 650.0 649.8 649.6 649.4 649.2 649.0 648.8

5,000

10,000 15,000 Live Storage (m3)

20,000

25,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-29

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Center West Business Park

Facility Type

Dry Pond (controlled surge pond)

Location

South of 94 Avenue & West of 116 Street

Catchment Area

168 ha (design report) 105 ha (measured)

Year of Construction

2008 & 2015

Neighbourhood Development Stage

City of Grande Prairie

Half of areas draining to this pond (Vision West Business Park, Central West Business Park) are fully developed as per 2016 air photo.

Inlet / Outlet

Inlets: 600mm to the east (659.71m). Inlets / Outlets: 900mm to the north (659.59m) @ 94 Ave & 117 St. French Drain to the east (does it exist?)

Control Structure

Flow Rate is controlled by Hydrovex 350SVHV-2 (Design H=4.50m, Design Q=320L/s) at downstream outlet at MH 577832, at invert of 659.42m.

Into Pond: From the southeast along 116 St; from northwest corner. Out of Pond: No defined Emergency Overflow.

Overflow

Catchment area is 168.8 ha per design report. Design head of the control structure is 4.5m, but actuall head from the HWL is only 2.38m. Design live Storage is much higher than the actual storage based on LiDAR.

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

661.80

1.95

15,600

Pond Bottom

659.85

0.00

Building Flooding

No risk

N/A

100-year 24-hour

662.69

2.84

100-year 4-hour

662.53

2.68

Surface Overflow to Downstream

661.85

2.00

10,000

5-year 4-hour

661.77

1.92

9,300

Bottom

659.85

0.00

Design

Modeled / LiDAR

662.0 661.8 661.6 Water Elevation (m)

661.4 661.2 661.0 660.8

660.6 660.4 660.2 660.0 659.8 659.6

1,000

2,000

3,000

4,000 5,000 6,000 Live Storage (m3)

7,000

8,000

9,000

10,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-30

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Albinati Industrial

Facility Type

Forebay (Wet)

Location

East of 97 Street & North of 133 Avenue

Catchment Area

5 ha

Year of Construction

2003

City of Grande Prairie

All areas draining to this pond are fully developed. Some areas in the neighbourhood are Neighbourhood Development Stage not developed as per 2016 air photo. Inlet / Outlet

Control Structure

Inlets: 3.0 m wide armoured channel at SW corner Outlets: 3.0 m wide armoured channel at SE corner

NWL is controlled by invert of oulet ditch at Southeast corner (design elevation at 682.64m). Flow Rate is uncontrolled. Into Pond: None. Out of Pond: None.

Overflow Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

683.49

0.85

963

Normal Water Level (NWL)

682.64

0.00

Pond Bottom

681.14

-1.50

Design

Modeled / LiDAR Building Flooding

No risk

N/A

Surface Overflow to Downstream

683.80

1.16

12,400

100-year 24-hour

683.29

0.65

300

100-year 4-hour

683.29

0.65

300

5-year 4-hour

683.01

0.37

Normal Water Level (NWL)

682.64

0.00

684.0

Water Elevation (m)

683.8 683.6 683.4 683.2 683.0 682.8 682.6 682.4

2,000

4,000

6,000 8,000 Live Storage (m3)

10,000

12,000

14,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-31

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Stone Ridge

Facility Type

Wet Pond

Location

South of 67th Avenue & West of Stone Ridge Way

Catchment Area

14 ha

Year of Construction

2016

City of Grande Prairie

The area draining into this pond is still being developed (North of Stone Ridge is 70% Neighbourhood Development Stage developed, areas south and west of the pond is undeveloped). Inlets: 600mm to the northwest (648.63m). Outlets: 600mm to the east (648.58m) to Pond 37.

Inlet / Outlet

NWL is controlled by downstream invert of 600mm pipe at the outlet of Pond 37 (650.28m). Flow Rate is eventually controlled by the size of the outlet pipe of Pond 37.

Control Structure

Into Pond: From the northwest near 600mm inlet via a swale; from northeast corner. Out of Pond: Emergency Overflow to the east at 653.73m (from LiDAR), overflowing into Pond 37.

Overflow

Design Drawing shows Freeboard at 653.30 m.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

651.48

1.20

13,430

NWL

650.28

0.00

Pond Bottom

648.28

-2.00

Design

Modeled / LiDAR Building Flooding

N/A

Surface Overflow to Downstream

653.30

5.02

45,700

100-year 24-hour

651.06

2.78

8,100

100-year 4-hour

650.93

2.65

6,500

5-year 4-hour

650.56

2.28

2,600

Bottom

648.28

0.00

653.5

Water Elevation (m)

653.0 652.5 652.0 651.5

651.0 650.5 650.0

5,000

10,000

15,000

20,000 25,000 30,000 Live Storage (m3)

35,000

40,000

45,000

50,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-32

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Stone Ridge

Facility Type

Wet Pond

Location

South of 67th Avenue & East of Stoneridge Way

Catchment Area

8 ha (direct)

Year of Construction

2016

City of Grande Prairie

Neighbourhood Development Stage The area draining into this pond is still being developed.

Inlet / Outlet

Control Structure

Overflow

Inlets: 600mm to the northwest (648.60m) from Pond 36. Outlets: 600mm to the southeast (648.64m).

NWL is controlled by downstream invert of 600mm pipe at the outlet (650.28m). Flow Rate is the size of the outlet pipe. Into Pond: From Pond 36 at the west near 600mm inlet. Out of Pond: Emergency Overflow to the southeast at 652.78m (from LiDAR) or 652.20m (from design), overflowing to the road right of way. This might change when the area is developed.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

651.48

1.20

2,170

Normal Water Level (NWL)

650.28

0.00

Pond Bottom

649.28

-1.00

Design

Modeled / LiDAR Building Flooding

N/A

Surface Overflow to Downstream

652.78

2.50

7,000

100-year 24-hour

651.18

0.90

1,100

100-year 4-hour

651.08

0.80

900

5-year 4-hour

650.54

0.26

200

Normal Water Level (NWL)

650.28

0.00

653.0

Water Elevation (m)

652.5 652.0

651.5 651.0 650.5 650.0

1,000

2,000

3,000

4,000 5,000 Live Storage (m3)

6,000

7,000

8,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-33

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Vision West Business Park

Facility Type

Dry Pond (controlled surge pond)

Location

South of 120 Street & 97 Avenue

Catchment Area

30 ha

Year of Construction

2010 - 2013

Neighbourhood Development Stage

City of Grande Prairie

Areas draining to this pond (Southwest of Vision West Business Park) are partially developed. Southeast area of the pond are still under construction as per 2016 air photo. Inlets: Overland drainage from swales to the northwest and northeast of the pond. Inlets / Outlets : 900mm to the west pond (660.36m); 900mm to the east pond (660.37m).

Inlet / Outlet

Control Structure

Flow Rate is not controlled. Others: A normally closed 200mm flow bypass (655.05m) with valve located at MH96205 allows the draining of the pond to the downstream storm sewers.

Overflow

Into Pond: None. Out of Pond: Emergency Overflow to the east at 662.49m (from LiDAR) overflowing to a ditch then to Pond #33.

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

662.20

1.40

Pond Bottom

660.80

0.00

N/A

100-year 24-hour

662.90

2.10

100-year 4-hour

662.87

2.07

Surface Overflow to Downstream

662.20

1.40

10,300

5-year 4-hour

662.15

1.35

9,800

Bottom

660.80

0.00

Design

Modeled / LiDAR Building Flooding

662.4 662.2

Water Elevation (m)

662.0 661.8 661.6 661.4 661.2 661.0 660.8

660.6

2,000

Note: Stage Storage data from LiDAR (2014)

4,000

6,000 Live Storage (m3)

8,000

10,000

12,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-34

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

N/A

Facility Type

Dry Pond (controlled surge pond)

Location

West of 116 Street & South of Railway near 89 Avenue

Catchment Area

50 ha

Year of Construction

2016

City of Grande Prairie

This pond only picks up the roadway drainage along 116 Street south of the Railway. A Neighbourhood Development Stage large undeveloped land southwest of the pond drains directly into it. Inlet / Outlet

Inlets / Outlets: 750mm to the southeast (660.62m);

Control Structure

Flow Rate is controlled by an 280mm orifice plate ((Design Q=230L/s at 2.1m Head)) just downstream of MH57186, which is followed by a 800mm CSP pipe.

Overflow

Into Pond: From the surrounding land to the pond Out of Pond: Emergency Overflow to the northeast at 662.98m (from LiDAR) or 662.60m (from design drawings), overflowing to the south ditch along Railway.

Comments

Water Elevation

Depth to Bottom

Total Live Storage

(m)

(m3)

High Water Level (HWL)

661.71

1.09

1,800

Pond Bottom

660.62

0.00

Design

Modeled / LiDAR Building Flooding

N/A

100-year 24-hour

663.25

2.63

100-year 4-hour

663.11

2.49

Surface Overflow to Downstream

662.98

2.36

6,400

5-year 4-hour

661.22

0.60

800

Bottom

660.62

0.00

663.2 663.0 662.8

Water Elevation (m)

662.6 662.4 662.2 662.0 661.8 661.6 661.4 661.2 661.0 660.8 660.6 660.4

1,000

2,000

3,000 4,000 Live Storage (m3)

5,000

6,000

7,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-35

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Royal Oaks

Facility Type

Wet Pond

Location

South of 132 Avenue & East of 108 Street

Catchment Area

75 ha

Year of Construction

2012

City of Grande Prairie

Half of the areas draining to this pond (North of Royal Oaks) are fully developed. The rest Neighbourhood Development Stage is still being developed. Inlet / Outlet

Inlets: 2X600mm to the southeast (660.10m); 900mm to the southeast (660.08m); 2x900mm pipes to the north overflowing from Pond 48. Outlets: 900mm to the northwest (655.20m) to Pond 47.

Control Structure

NWL is controlled by invert of a weir at the downstream MH of the 900mm outlet pipe (Elevation: 662.70m). Flow Rate is controlled by a 330mmx330mm orifice plate further downstream at the inlet pipe to Pond 47.

Overflow

Into Pond: From the southeast near both 600mm inlets and the 900mm inlet; from 132 Ave and 108 St at the northwest cornor. Out of Pond: Emergency Overflow to the northwest at 664.16m (from LiDAR) or 664.30m (from design drawings).

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

664.30

1.60

63,800

Normal Water Level (NWL)

662.70

0.00

Pond Bottom

660.70

-2.00

Design

Modeled / LiDAR Building Flooding

No risk

N/A

100-year 24-hour

664.52

1.82

100-year 4-hour

664.42

1.72

Surface Overflow to Downstream

664.16

1.46

54,700

5-year 4-hour

663.89

1.19

42,900

Normal Water Level (NWL)

662.70

0.00

664.6 664.4

Water Elevation (m)

664.2

664.0 663.8 663.6 663.4 663.2 663.0 662.8 662.6

10,000

20,000

30,000 40,000 Live Storage (m3)

50,000

60,000

70,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-36

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Hidden Valley

Facility Type

Wet Pond

Location

West of 108 Street & South of Bear Creek

Catchment Area

25 ha (Current)

Year of Construction

2017

City of Grande Prairie

Neighbourhood Development Stage Most of the areas draining to this pond is being developed. Inlets: 1650mm to the northwest (665.16m) of south cell Outlets: 1200mm to the northeast (655.80m) of north cell.

Inlet / Outlet

Control Structure

NWL and Flow Rate are controlled by Series 95 Fontaine Stop Logs as part of a water control gate, which is followed by a 1050mm pipe. Into Pond: From the southeast conor of south pond. Out of Pond: Emergency Overflow at the northeast corner of north pond at 661.42m (from LiDAR) or 661.30m (from design drawings).

Overflow

Pond live storage estimated from LiDAR is much smaller than the design storage.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

659.75

1.50

12,200

Normal Water Level (NWL)

658.25

0.00

Pond Bottom

655.50

-2.75

Design

Modeled / LiDAR Building Flooding

No risk

N/A

Surface Overflow to Downstream

661.42

3.17

10,900

100-year 24-hour

659.98

1.73

4,000

100-year 4-hour

659.65

1.40

2,900

5-year 4-hour

658.71

0.46

2,200

Normal Water Level (NWL)

658.25

0.00

659.4

Water Elevation (m)

659.2 659.0 658.8 658.6 658.4 658.2

1,000

2,000

3,000 Live Storage (m3)

4,000

5,000

6,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-37

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Trader Ridge

Facility Type

Wet Pond

Location

132 Ave & 103 St

Catchment Area

63 ha

Year of Construction

2016

City of Grande Prairie

Neighbourhood Development Stage The area draining into this pond is still being developed.

Inlet / Outlet

No information available.

Control Structure

No information available.

Overflow

No information available.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

Design High Water Level (HWL)

678.18

34,770

Unknown

676.60

Building Flooding

100-year 4-hour

Normal Water Level (NWL) Pond Bottom Modeled / LiDAR

100-year 24-hour

678.48

5-year 4-hour

Normal Water Level (NWL)

Surface Overflow to Downstream

678.4 678.2

Water Elevation (m)

678.0 677.8 677.6 677.4 677.2 677.0

676.8 676.6 676.4

10,000

20,000

30,000 Live Storage (m3)

40,000

50,000

60,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-38

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Oâ&#x20AC;&#x2122;Brien Lake

Facility Type

Wet Pond

Location

South of 59 Avenue & 113 Street

Catchment Area

26 ha

Year of Construction

2013

City of Grande Prairie

Neighbourhood Development Stage The area draining into this pond is still being developed.

Inlet / Outlet

Inlets: 1050mm to the northwest (647.11m); drainage ditch to the northeast. Outlets: 750mm to the southwest (655.80m) then a 900mm to creek.

Control Structure

NWL is controlled by weir invert at the outlet structure (649.40m). Flow Rate is controlled by rectangular 600mm(width) x 400mm (height) orifice plate at 648.70mm with overflow weir at 651.10m at outlet structure.

Overflow

Into Pond: None. Out of Pond: Emergency Overflow to the southwest at 651.45m (from LiDAR) to creek.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

651.10

1.70

27,790

Normal Water Level (NWL)

649.40

0.00

Pond Bottom

647.40

-2.00

Design

Modeled / LiDAR Building Flooding

N/A

Surface Overflow to Downstream

651.45

2.05

31,900

100-year 24-hour

650.04

0.64

8,000

100-year 4-hour

649.90

0.50

6,200

5-year 4-hour

649.61

0.21

2,500

Normal Water Level (NWL)

649.40

0.00

651.8 651.6

Water Elevation (m)

651.4 651.2

651.0 650.8 650.6 650.4 650.2 650.0 649.8 649.6 649.4 649.2

5,000

10,000

15,000 20,000 Live Storage (m3)

25,000

30,000

35,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-39

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Arbour Hills

Facility Type

Wet Pond

Location

North of 132 Avenue & West of Arbour Hills Blvd.

Catchment Area

6 ha

Year of Construction

2016

City of Grande Prairie

Neighbourhood Development Stage The area draining into this pond is still being developed. Inlets: 450mm to the northwest (661.02m); 600mm to the north (660.72m); 1500mm to the northeast (660.00m); 1200mm to the southeast (660.10m) from east Pond #47. Outlets: 1050mm to the southwest (660.57m).

Inlet / Outlet

NWL is controlled by outlet pipe invert (662.32m). Flow Rate is controlled by downstream sewer system, 750mm pipe.

Control Structure

Into Pond: From 132 Avenue from southeast corner. Out of Pond: Emergency overflow to 132 Avenue at 663.95m (LiDAR) from the southwest corner.

Overflow

As shown in City's database, only the 1200mm inlet pipe and 1050mm outlet pipe were modeled.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

664.30

1.98

21,000

Normal Water Level (NWL)

662.32

0.00

Pond Bottom

660.32

-2.00

N/A

Surface Overflow to Downstream

663.95

1.63

16,400

100-year 24-hour

663.77

1.45

14,000

100-year 4-hour

663.69

1.37

13,100

5-year 4-hour

663.69

1.37

13,100

Normal Water Level (NWL)

662.32

0.00

Design

Modeled / LiDAR Building Flooding

665.5

Water Elevation (m)

665.0 664.5

664.0 663.5 663.0 662.5

662.0

5,000

10,000

15,000 20,000 25,000 Live Storage (m3)

30,000

35,000

40,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-40

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Arbour Hills

Facility Type

Wet Pond

Location

North of 132 Avenue & West of 108 Street

Catchment Area

9 ha

Year of Construction

2016

City of Grande Prairie

Neighbourhood Development Stage The area draining into this pond is still being developed.

Inlet / Outlet

Control Structure

Overflow Comments

Inlets: 900mm to the east (660.80m) from Pond #48; 600mm to the southeast (660.80m) from Pond #41 and Pond #48. Outlets: 1200mm to the southwest (660.50m) to Pond #46.

NWL is controlled by outlet pipe invert (662.70m). Flow Rate is controlled by downstream sewer system. Into Pond: From 132 Avenue at southeast corner. Out of Pond: No information provided. Pond is not fully developed yet. Pond surroundings is not completed.

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

664.30

1.60

7,100

Normal Water Level (NWL)

662.70

0.00

Pond Bottom

660.70

-2.00

Design

Modeled / LiDAR Building Flooding

N/A

Surface Overflow to Downstream

665.20

2.50

13,700

100-year 24-hour

664.00

1.30

5,400

100-year 4-hour

663.93

1.23

4,900

5-year 4-hour

663.69

0.99

3,700

Normal Water Level (NWL)

662.70

0.00

665.5

Water Elevation (m)

665.0 664.5 664.0 663.5 663.0 662.5

2,000

4,000

6,000 8,000 Live Storage (m3)

10,000

12,000

14,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-41

Appendix C - Stormwater Management Facility Summary Sheets Pond ID

Storm Drainage Master Plan 2018 Neighbourhood

Arbour Hills

Facility Type

Wet Pond

Location

North of 132 Avenue & East of 108 Street

Catchment Area

24 ha (current)

Year of Construction

2014

City of Grande Prairie

Neighbourhood Development Stage Inlets: 900mm (661.00m) to the southeast; 600mm (666.40) culvert to the northeast. Outlets: 2x900mm (663.40m) culverts to the south to Pond #41; 600mm to the southwest (661.30m) and 900mm to the west (611.30m) to Pond #47.

Inlet / Outlet

NWL is controlled by 600mm outlet pipe invert (663.70m), and the weir invert (663.70m) at outlet structure downstream of 900mm outlet pipe. Flow Rate is controlled by the weir downstream of the 900mm outlet and the orifice downstream of the 600mm oulet. Into Pond: From 132 Avenue from southeast corner. Out of Pond: Emergency overflow to 132 Avenue at 665.72m (from LiDAR) or 665.20m (from design drawings).

Control Structure

Overflow

The northeast 600mm culvert is not modeled as it is not included in City's Database.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

664.30

0.60

5,080

Normal Water Level (NWL)

663.70

0.00

Pond Bottom

661.20

-2.50

Design

Modeled / LiDAR Building Flooding

N/A

Surface Overflow to Downstream

665.20

1.50

15,200

100-year 24-hour

664.67

0.97

9,400

100-year 4-hour

664.48

0.78

7,200

5-year 4-hour

663.88

0.18

1,400

Normal Water Level (NWL)

663.70

0.00

665.4 665.2 Water Elevation (m)

665.0 664.8 664.6 664.4 664.2 664.0 663.8 663.6

2,000

4,000

6,000

8,000 10,000 Live Storage (m3)

12,000

14,000

16,000

18,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-42

Appendix C - Stormwater Management Facility Summary Sheets

Storm Drainage Master Plan 2018

Pond ID

Neighbourhood

Fieldbrook

Facility Type

Wet Pond

Location

East end of 84 Avenue

Catchment Area

7.2 ha + Creek from N

Year of Construction

2013

City of Grande Prairie

Neighbourhood Development Stage The areas draining into the pond is not developed yet. Inlets: 600mm to the southwest. Outlets: 2.4m x 1.2 m box culvert at south end of pond to control structure.

Inlet / Outlet

NWL is controlled by weir invert (650.50m) at control structure. Flow Rate is controlled by the weir at the control structure.

Control Structure

Into Pond: From 84a Avenue from west. Out of Pond: Emergency overflow to downstream south ditch at 652.93m (from LiDAR).

Overflow

Inlet pipe was not modeled as it is not included in City's database.

Comments

Water Elevation

Depth to NWL

Total Live Storage

(m)

(m3)

High Water Level (HWL)

652.05

1.55

8,300

Normal Water Level (NWL)

650.50

0.00

Pond Bottom

648.00

-2.50

Design

Modeled / LiDAR Building Flooding

N/A

100-year 24-hour

653.10

2.60

Surface Overflow to Downstream

652.93

2.43

16,000

100-year 4-hour

652.92

2.42

15,900

5-year 4-hour

651.64

1.14

5,200

Normal Water Level (NWL)

650.50

0.00

653.5

Water Elevation (m)

653.0 652.5 652.0 651.5 651.0 650.5

650.0

2,000

4,000

6,000

8,000 10,000 Live Storage (m3)

12,000

14,000

16,000

18,000

Note: Stage Storage data from LiDAR (2014).

Sameng Inc.

C-43

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Appendix D: Detailed Assessment of High Flood Risk Areas

Sameng Inc.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 1 â&#x20AC;&#x201C; Northridge (southeast) Main Flood Mechanisms and Flood Risk Areas Surface drainage in most of Northridge converges to a ditch located between 100 Street and 102 Street flowing south. This means that if the storm sewers cannot capture all the runoff (5-year event and larger), the major drainage overflow will get here. Unfortunately, modeling results suggest that the amount of water trying to flow into this ditch during extreme events is much larger than the ditch capacity and poses a flood risk to the surrounding areas. Topography

A 100 Street

124 Avenue

102 Street

C 116 Avenue / HWY 43

Sameng Inc.

D-1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 1 â&#x20AC;&#x201C; Northridge (southeast) Area A (124 Avenue): During a 5-year and 100-year event, these two depressions will fill with more than 50cm of water and overflow south into a ditch between two private properties and towards 121 Avenue and into Area B. Most of the surface water flowing to this depression comes from the north via 100 Street and 101 Street. At the peak of the 100-year runoff event, the model estimates close to 4,100 L/s flowing towards this area, which is significant. It should be noted that, although a 1050mm pipe services the easternmost depression of 124 Avenue, this area is lower than the ground elevation on 100 Street where the downstream pipe is located. Consequently, if the pipe on 100 Street is surcharged near grade (which happens during both the 5-year and 100-year events), this depression cannot be drained out via the pipe, and water from the downstream system may even backflow into this depression. Two buildings appear to be at risk of flooding due to the large ponding depths, as well as many parking stalls. All other buildings appear to be high enough and should not flood.

61cm

100 Street

102 Street

101 Street

See Section 8.3.1 for the improvement concept.

124 Avenue

Sameng Inc.

75cm

D-2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 1 â&#x20AC;&#x201C; Northridge (southeast) Area B (121 Avenue): During a 100-year event, this depression will fill with about 102 cm of water (64cm during 5-year event). During both the 5-year and 100-year events, the ponding overflows south into a ditch between private properties and towards 117 Avenue through Area C. Most of the surface water flowing to this depression comes from the east from 100 Street, as well as the ditch conveying overflow from Area A. The model suggests that more than 5,000 L/s of water flows into this depression during a 100-year event, which is a very large quantity of water. Many of the townhouse units as well as many parking stalls in this complex as well as the parking lot south of 121 Avenue are at risk. The building southeast of the 121 Avenue and 102 Street intersection also appears to be at risk. It should be noted that the townhouses are at risk of flooding not only due to the large ponding depths, but also due to capacity restrictions in the ditch north of 121 Avenue (ditch too small).

100 Street

See Section 8.3.1 for the improvement concept.

102cm 121 Avenue

102 Street

89cm

Sameng Inc.

D-3

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 1 â&#x20AC;&#x201C; Northridge (southeast) Area C (Between 117 Avenue and 121 Avenue): During a 100-year event, this area may see more than 50cm of water pooling in the parking lots (but generally less than 35cm during the 5-year event). This is because this commercial development is located in a large depression with poor major drainage overflow. Furthermore, the south flowing ditch appears to become shallower and less defined closer to 117 Avenue, and overflows onto the adjacent properties. Along 100 Street, a large ponding area is also observed near the motel. This large ponding extent will likely flood many cars parked on the commercial site. A few of the buildings are also at-risk of flooding. See Section 8.3.1 for the improvement concept.

100cm

100 Street

120 Avenue

77cm

102 Street

94cm

Sameng Inc.

D-4

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 1 â&#x20AC;&#x201C; Northridge (southeast) Area D (116 Avenue at 102 Street): During a 100-year event, this area may see more than 89cm of water pooling on 116 Avenue (Highway 43) (72cm during 5-year event). During both the 5-year and 100-year events, the ponding overflows south via 102 Street and into the Avondale neighbourhood (Location 2). At the peak of the 100-year event, the water overflows at a rate of 7,200 L/s into Avondale, which is very significant. This large ponding extent may flood vehicles driving on the road, and completely prevent vehicles from driving on this important highway as the ponding depths will be too deep to pass safely, even for emergency vehicles. A few buildings to the northeast appear to be at risk from the large ponding depths. See Section 8.3.1 for the improvement concept.

117 Avenue

116 Avenue / HWY 43

102 Street

89cm

Sameng Inc.

D-5

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 2 â&#x20AC;&#x201C; Avondale / Montrose Main Flood Mechanisms and Flood Risk Areas Most of the Avondale and Montrose neighbourhoods are at some level of flood risk due to large major drainage flows, the many depressions which fill with water, poor private lot grading and the lack of capacity in the storm sewer system. Topography in the area slopes southwest towards Bear Creek. - Major Drainage Overflow: A significant amount of major drainage overflow from the north (from 116 Avenue / Highway 43) via 99 Street (1.6m3/s), 100 Street (1.2m3/s) and especially 102 Street (7.2m3/s) flows into Avondale. This major drainage flow combines with runoff originating from Avondale and South Avondale to result in very large surface flows (generally 1 to 4 m3/s) and flow depths (generally 15 to 30cm) on most streets in the neighbourhoods. This drainage fills all street depressions along the way and eventually makes its way in a southwest direction into Bear Creek via the ground surface, generally between 108 Avenue and 100 Avenue. - Flooding at Depressions: Many depressions in the area are susceptible of flooding in excess of 35cm during a 100-yr event, but most of the flooding is quite localized with only a few residences at risk of flooding at each depression. The map below shows 15 locations where ponding in excess of 35cm in anticipated; some of these locations will even have ponding exceeding 50cm. - Poor Lot Grading: The elevation of private properties in this mature neighbourhood is generally quite flat in comparison with the road. Consequently, a ponding (or flowing) water depth above the curb height (more than 15cm) can flood some low-lying properties and residences. In newer subdivisions, houses are generally well graded and are much higher than the road elevation.

Sameng Inc.

D-6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 2 â&#x20AC;&#x201C; Avondale / Montrose

100 Street Avenue

102 Street Avenue

104 Street Avenue

116 Avenue / HWY 43

108 Avenue

Topography

Sameng Inc.

D-7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 2 â&#x20AC;&#x201C; Avondale / Montrose Area A (111/112 Avenue near 103 Street): During a 100-year event, the depressions between 102 and 104 Street fill with water and overflow to the south via a narrow walkway and then through the school yard to the south. The large ponding depths and extents, combined with the large surface flows, pose a high flood risk to the area. Many residences are at risk of flooding in the area during a 100-year event, and a few during a 5-year event. Vehicles parked on the street or on driveways are also at risk. See Section 8.3.1 and 8.3.2 for the improvement concepts.

73cm

102 Street

104 Street

113 Avenue

112 Avenue

54cm

111 Avenue

41cm

110 Avenue

Sameng Inc.

D-8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 2 â&#x20AC;&#x201C; Avondale / Montrose Area B (105/110 Avenue near 102 Street): During a 100-year event, many small depressions in this area will fill with water and overflow either via the roads or through private properties. The peak surface flow flowing south on 102 Street exceeds 4,000 L/s and this flow divides into all the local roads such that street flow depths generally exceed 15cm. The large ponding depths and extents, combined with the large surface flows, pose a high flood risk to the area, as shown in the figure below. Many residences and properties are at risk of flooding in the area during a 100-year event, and a few during a 5-year event. Vehicles parked/driving on the street or on driveways are also at risk. See Section 8.3.1 and 8.3.2 for the improvement concepts.

110 Avenue

46cm

108 Avenue

102 Street

104 Street

52cm

48cm

57cm

64cm

52cm

46cm

Sameng Inc.

D-9

106 Avenue

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 2 â&#x20AC;&#x201C; Avondale / Montrose Area C (100 Street from 108 to 113 Avenue): During a 100-year event, many depressions in this area will fill with water and overflow either via the roads or through private properties. The main reason for all these properties flooding is the large amount of water overflowing the tracks from the east (see Location 4, Area B) (more than 4,000 L/s at the peak runoff) and making its way west on 112 Avenue (after flowing over the high point at the 99 Street intersection) and then south on 100 Street. The east service road of 100 Street is quite at risk. The large ponding depths and extents, combined with the large surface flows, pose a high flood risk to the area, as shown in the figure below. Many residences, buildings and properties are at risk of flooding in the area during a 100year event, and a few during a 5-year event. Vehicles parked/driving on the street or on driveways are also at risk.

112 Avenue

100 Street

56cm

97cm 108 Avenue

Sameng Inc.

D-10

Railroad

See Section 8.3.1 and 8.3.2 for the improvement concepts.

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 3 â&#x20AC;&#x201C; Highland Park Main Flood Mechanisms and Flood Risk Areas The Highland Park neighbourhood is at risk of flooding for many reasons including a lack of capacity in the sewer system (pipes in the area are small and surcharged to ground during the 5-year or larger events), the fact that sewers flow towards an area with higher ground elevation (some sewer flow west while topography slopes east), and poor major drainage overflow (including many large depressions). Poor private lot grading is also a flood risk factor for some of these lots. Topography in the area is generally to the east through what appears to be an extension of the Woody Channel.

96 Avenue Topography

99 Street Avenue

100 Street Avenue

92 Avenue

88 Avenue

Sameng Inc.

D-11

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 3 â&#x20AC;&#x201C; Highland Park Area A (96 Avenue east of 100 Street): During a 100-year event, this depression will fill with just over 1.0 metre of water, and up to 65cm of water is expected during the 5-year event. This ponding overflows south onto 100 Street towards Area B. Most of the surface water flowing to this depression comes from the northeast via 99 Street (peak surface runoff of 2,600 L/s). Water is anticipated to pool at this depression for more than 4 hours during the 100-year event. One of the main reasons why this area floods and water pools on the street for several hours, is that this depression must flow through a small piped system that is flowing west towards an area with higher elevation before reaching the outfall. This is a concern because if the downstream system is surcharged to ground, there is no capacity to drain this depression, and water might actually backflow from the downstream end of the system into this depression. Model simulation results suggests that is the case during the 100-year event, as illustrated in the profile figure below. See Section 8.3.3 for the improvement concept.

Depression at 96 Avenue Backflow into depression

Higher ground elevation downstream (about 1m higher)

Due to the large ponding depths and extent, many residences and buildings are at risk of flooding in the area during a 100-year event, and a few during a 5-year event. Vehicles parked/driving on the street or on driveways are also at risk.

Sameng Inc.

D-12

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

100 Street

Location 3 â&#x20AC;&#x201C; Highland Park

96 Avenue

103cm

Sameng Inc.

D-13

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 3 â&#x20AC;&#x201C; Highland Park Area B (99 Street at 93/94 Avenue, and west of 100 Street): During a 100-year event, this large depression will fill with 86cm of water, and about 54cm is expected during the 5-year event. This ponding overflows south onto 99 Street towards Area D. Most of the surface water flowing to this depression comes from the northwest (100 Street / 94 Avenue). Water is anticipated to pool at this depression for more than 4 hours during the 100-year event. Similar to Area A, one of the main reasons why this area floods and water pools on the street for several hours, is that this depression must flow through a small piped system that is flowing west towards an area with higher elevation before reaching the outfall. Due to the large ponding depths and extent, many residences and buildings are at risk of flooding in the area during a 100-year event, and a few during a 5-year event. Vehicles parked/driving on the street or on driveways/parking lots are also at risk. Further to the west of 100 Street at 92 Avenue and 93 Avenue, some small depressions seem to pose a flood risk to the surrounding residences, although the ponding depths are quite reasonable. The area floods because the downstream sewers are very surcharged. See Section 8.3.3 for the improvement concept.

99 Street

100 Street

94 Avenue

38cm

37cm

86cm

92 Avenue

Sameng Inc.

D-14

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 3 â&#x20AC;&#x201C; Highland Park Area C (94 Avenue west of Resources Road): During a 100-year event, this depression will fill with 95cm of water on the street, and about 41cm is expected during the 5-year event. This ponding overflows west along 94 Avenue into the Area B depression, but will cause much flooding in the area prior to doing so. Water comes into this depression mostly due to backwater from the downstream sewers along Resources Road (water flows out of the catchbasins onto the street), as well as some major drainage overflow from the east. Due to the large ponding depths and extent, some buildings and parking lots are at risk of flooding to the south of 94 Avenue. North of 94 Avenue, a large trailer home site also appears to be at a high risk of flooding. Vehicles parked/driving on the street or on driveways/parking lots are also at risk. See Section 8.3.3 for the improvement concept.

94 Avenue

95cm

Sameng Inc.

D-15

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 3 â&#x20AC;&#x201C; Highland Park Area D (Near 91 Avenue and 98 Street): During a 100-year event, this very large depression in a green space will fill with up to 126cm of water, and up to 73cm is expected during the 5-year event. This ponding overflows southeast to 88 Avenue, across 98 Street and Resources Road, and into the Woody Channel. In overflowing to the southeast, the water needs to cross a few roads and high points along the way, which will create some pooling of water in the green space. This pooling is expected to flood some yards, but it generally stays away from most houses. A few houses may be at risk of flooding along the way during the most extreme events, and the school to the southeast of the figure is also at risk. In the area of 90 and 91 Avenue, many residences appear to be at risk of flooding. This area received major drainage overflow from an area to the south, in excess of 2,500 L/s during a 100-year event. This water overflows into the green space discussed above, but it might still flood many homes in the process of overflowing.

99 Street

See Section 8.3.3 for the improvement concept.

119cm

109cm

126cm

98 Street

54cm

Sameng Inc.

D-16

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 4 â&#x20AC;&#x201C; Mountview (west) and Crystal Ridge (southwest) Main Flood Mechanisms and Flood Risk Areas Part of the Mountview and Crystal Ridge neighbourhoods along the railroad tracks are at an enhanced flood risk due to large major drainage flows in the area and lack of sewer capacity downstream. Topography in the area is generally to the west towards the railroad, and then south. 119A Avenue

Railroad

96 Street

116 Avenue

112 Avenue

Railroad

Topography

108 Avenue

Sameng Inc.

D-17

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 4 â&#x20AC;&#x201C; Mountview (west) and Crystal Ridge (southwest) Area A (west of 98 Street and north of 116 Avenue): The southwest corner of Crystal Ridge is at the downstream end of the major drainage system of Crystal Ridge. At the peak 100-year runoff, the swale along the east of the railroad conveys 4,600 L/s towards 116 Avenue; 1,100 L/s comes from the dry pond in Scenic Ridge (123 Avenue and 98 Street) which overflows during the 100-year event. Part of this water overflows to the west onto 116 Avenue; part of it overflows south along the east of the railroad into Mountview and into Area B. During a 5-year event, the peak runoff is only 900 L/s towards 116 Avenue and 116 Avenue does not overflow. Many residences backing on to the railroad swale are at-risk of flooding from the large volume of major drainage overflow going towards 116 Avenue, as well as major drainage overflowing from the local roads towards that swale. See Section 8.3.1 for the improvement concept.

119A Avenue

98 Street

Railroad

91cm

118 Avenue

106cm

116 Avenue

Sameng Inc.

D-18

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 4 â&#x20AC;&#x201C; Mountview (west) and Crystal Ridge (southwest) Area B (west of 97 Street and south of 116 Avenue): A lack of capacity in the downstream storm sewer system (pipes surcharged to grade during 5-year event), a lack of storage capacity in the SWMF (overflows during 5-year event), a large influx of major drainage flow from the north and east, and the presence of the railroad blocking major drainage overflow to the west are the main flood mechanisms. - Major Drainage Overflow: During a 100-year rainfall event, an estimated 2 m3/s of runoff comes from the north of the neighbourhood and into the SWMF (swale east of railroad). This surface drainage originates from the area north of 116 Avenue in Crystal Village (Area A). This large flow and flow depth in the green space east of the railroad (from 116 Avenue to the SWMF) has the potential to flood properties in Mountview. A significant amount of major drainage flow also comes from Mountview towards the SWMF (about 9.5 m3/s during 100-year event). - SWMF: The Mountview surge pond (SWMF #4) fills up and overflows as it is quite under capacity to handle all this flow. Modeling results suggest that the pond overflows during a 1:5-year event. - Overflow out of Mountview: Major drainage overflow out of this area is to the west across the railroad, just west of the Mountview SWMF. Many properties and residences backing onto that railroad will be at risk of flooding if the railroad overflows; flooding will mostly affect backyards, with more than 50cm of water pooling in some areas. The railroad overflow makes its way through the Avondale neighbourhood (Location 2), which also has significant flood risks. Substantial overflow of the railroad is anticipated during a 100-year event, but not for the 5-year event. Flood risks also exist during a 5-year event, but they are minimal. It should also be noted that large street flows and velocities in vicinity of the SWMF are a risk to the public. See Section 8.3.1 and 8.3.2 for the improvement concepts. 116 Avenue

155cm

113 Avenue 55cm

44cm

111 Avenue

97 Street

63cm

Railroad

97 Street

Railroad

94cm

55cm 108 Avenue Sameng Inc.

D-19

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 5 â&#x20AC;&#x201C; Crystal Heights and Ivy Lake Estates Main Flood Mechanisms and Flood Risk Areas Localized depressions with a lack of proper major drainage is the main reason for flooding in Crystal Heights and Ivy Lake Estates. Topography slopes from north to south into a SWMF at the southeast corner of the Ivy Lake Estates neighbourhood. 112 Avenue

Topography

108 Avenue

104 Avenue

Sameng Inc.

D-20

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 5 â&#x20AC;&#x201C; Crystal Heights and Ivy Lake Estates Area A (east of 88C Street near 110 Avenue): This depression in the green alleys collects major drainage from a large area northwest of Crystal Heights. Model results suggest that this area is a risk of flooding due to the large surface flow (3,300 L/s during 100-year event) and poor major drainage. The major drainage is believed to cross the 88 Street ROW via a culvert, but this culvert is undersized, resulting in ponding. The maximum ponding depth in the green alley is 82cm during a 100-year event, and 62cm during a 5-year event. A few residences and some backyards are at risk of flooding in the area during a 100-year event. Flood risks are quite low during a 5-year event.

112 Avenue

45cm

46cm

88C Street

82cm

110 Avenue

Sameng Inc.

49cm

D-21

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 5 â&#x20AC;&#x201C; Crystal Heights and Ivy Lake Estates Area B (103 Avenue at 88C Street): This street depression collects major drainage overflow from 88C Street to the north (3,000 L/s at peak 100-year runoff) and will flood the surrounding residences. The ponding depth is expected to reach 75cm during a 100-year event (14cm during 5-year event). This water will overflow the properties to the south and flow into the pond. The large ponding depths may even flood some vehicles parked on the street and even on private property. The flood risks during a 5-year event are quite negligible as there is not much major drainage flows reaching the area (the sewers can generally handle these flows).

104 Avenue

75cm

Sameng Inc.

D-22

103 Avenue

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 5 â&#x20AC;&#x201C; Crystal Heights and Ivy Lake Estates Area C (104 Avenue at 90 Street): This street depression collects major drainage overflow from 90 Street to the north (3,400 L/s at peak 100-year runoff) and will flood the surrounding residences because of a poor major drainage design. The ponding depth is expected to reach 77cm during a 100-year event (40cm during 5-year event). This water will overflow the properties to the south and flow through the alley to the east then south and onto 102 Avenue and eventually into the pond. The large ponding depths may even flood some vehicles parked on the street and on private property. The flood risks during a 5-year event are quite small as there is not much major drainage flows reaching the area (the sewers can generally handle these flows).

45cm

77cm

Sameng Inc.

D-23

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 5 â&#x20AC;&#x201C; Crystal Heights and Ivy Lake Estates How to Reduce Flood Risks? An improvement concept was not developed/modeled for this area. It will be very challenging to establish a proper major drainage system for the area, although it may be possible to establish some overflow routes through private properties. The proposed upgrades will likely need to consist of pipes. Furthermore, there may be a possibility to divert the upstream flows into a future drainage basin east of the neighbourhoods. This would reduce major drainage flows reaching these depressions.

Sameng Inc.

D-24

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 6 â&#x20AC;&#x201C; Smith / Hillside (southeast) Main Flood Mechanisms and Flood Risk Areas Very large major drainage flows combined with local depressions is the main reason for flooding in the Smith and Hillside neighbourhoods. South of Smith (industrial area), a lack of proper major drainage flow and poor lot grading is the main reason for the enhanced flood risks. Topography in the area is generally from north to south towards ditches in the industrial development south of 92 Avenue. Topography

100 Avenue

92 Street

96 Avenue

B 92 Avenue

Sameng Inc.

D-25

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 6 â&#x20AC;&#x201C; Smith / Hillside (southeast) Area A (100 Avenue at 92 Street): The 100 Avenue and 92 Street intersection is a depression that collects a significant amount of flow; an estimated 8,000 L/s during a 100-year event. This results in a ponding depth of 60cm at the intersection and a large ponding extent in the area. The overflow from this depression is both east on 100 Avenue (2,400 L/s), south on 92 Street (4,000 L/s) and through the walkway to the southwest and into the Smith neighbourhood (3,000 L/s). Substantial major drainage flows (2,500 L/s) and overflows into the Smith neighbourhood are also expected during the 5-year event, due to a lack of sewer capacity on 92 Street (surcharged to grade during 5-year event). The large quantity of runoff flowing south along 92 Street and through the Smith neighbourhood threaten to flood many private properties and residences along the way. Fortunately, the major drainage path between Area A and Area B is quite well defined and few houses are at risk of flooding from these large surface flows, although ponding/flow depths in Smith are quite large and could flood many vehicles parked on the street. See Section 8.3.4 for the improvement concept.

92 Street 60cm

100 Avenue

Sameng Inc.

D-26

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 6 â&#x20AC;&#x201C; Smith / Hillside (southeast) Area B (92B Street at 93/94 Avenue): A significant amount of overflow from the north via 92B Street (4,000 L/s during 100-year event) causes significant ponding and flood risks at the south end of Smith. Ponding depths of 64cm on 94 Avenue and 71cm on 93 Avenue during the 100-year event (38cm and 19cm respectively for the 5-year event with much less overflow as the sewers can handle the flows) are anticipated. Flood risks during the 5-year event are negligible. See Section 8.3.4 for the improvement concept.

95 Avenue 92B Street 71cm

94 Avenue

93 Avenue

92 Avenue

Sameng Inc.

D-27

92 Street

64cm

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 6 â&#x20AC;&#x201C; Smith / Hillside (southeast) Area C (92 Avenue west of 92 Street): A significant amount of overflow from the north (from Area B) as well as from 92 Street (north) and 92 Avenue (east) combined with poor major drainage flows to the south causes substantial flooding in this industrial area, with most of the area being under a large depth of water (up to 100cm) during the 100-year event. Although not as severe as for the 100-year event, there are flood risks in the industrial area during a 5-year event, with ponding depths generally less than 35cm on private properties. See Section 8.3.4 for the improvement concept.

92 Avenue >50cm 92 Street

>50cm

Sameng Inc.

D-28

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 7 â&#x20AC;&#x201C; Patterson Place (southwest) Main Flood Mechanisms and Flood Risk Areas Many houses at the southwest corner of Patterson Place are at risk of flooding due to the large major drainage overflow from the northeast part of the neighbourhood that must pass through this area to overflow 100 Street and into the Creek. Topography in the area is from the northeast to the southwest.

Topography

99A Street

B 100 Street

Sameng Inc.

D-29

76A Avenue

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 7 â&#x20AC;&#x201C; Patterson Place (southwest) Area A, B & C (99A Street and 79 Avenue / 99A Street and 76A Avenue): At both the 99A Street and 79 Avenue bend as well as the 99A Street and 76A Avenue bend, major drainage collects and overflows through narrow passages between properties. In the process, the model suggest that a few houses and vehicles are at-risk of flooding from the high ponding depths during a 100-year event. Ponding depths are expected to reach 78cm at the 99A Street and 76A Avenue bend (40cm during 5-year) and 55cm at the 99A Street and 79 Avenue bend (40cm during 5-year). A couple more houses along 76A Avenue east of 77 Avenue, as well as the church west of 100 Street also appear to be at risk of flooding due to the large ponding depths in the area. During a 5-year event, the flood risks are minimal as there is little major drainage flows during that event and the ponding depths are reasonable, but still above 35cm in depth.

51cm

99A Street

55cm

100 Street

78cm

76A Avenue 47cm

50cm

Sameng Inc.

71cm

D-30

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 7 â&#x20AC;&#x201C; Patterson Place (southwest) How to Reduce Flood Risks? An improvement concept was not developed/modeled for this area. Given the small amount of properties at risk, and the fact that there are only flood risks during the most extreme rainfall events, a low-cost option should be investigated. This may consist of: 1- Improving (lowering/widening) the existing major drainage overflow paths to reduce ponding depths; 2- Upgrade the downstream storm sewers to convey the peak 100-year event with acceptable ponding at these locations. 3- Construct small pond(s) on existing park space to temporarily store the excess runoff. These improvement solutions were not modeled, or cost estimated.

Sameng Inc.

D-31

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 8 â&#x20AC;&#x201C; Country Club Estates Main Flood Mechanisms and Flood Risk Areas The Country Club Estates neighbourhood has a large depression in the middle of the neighbourhood at the intersection of Poplar Drive and 65 Avenue that poses a flood risk to adjacent properties due to large ponding depths and the lack of proper major drainage overflow. Topography throughout most of the neighbourhood slopes towards that depression.

94 Street

96A Street

68 Avenue

Topography

Sameng Inc.

D-32

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 8 â&#x20AC;&#x201C; Country Club Estates Area A (Poplar Drive and 65 Avenue): This area is susceptible to see about 90cm of water ponding on the street for many hours during a 100-year event (35cm during 5-year event) and flood many properties and residences in the area. This is because this depression has inadequate major drainage overflow, which is currently to the southeast. Most of the major drainage flows reaching this depression come from north of 68 Avenue (South Patterson Place), flowing to the south and into the depression at a peak rate of 1,900 L/s. During a 5-year event, the flood risks are minimal as there is little major drainage flows during that event and the ponding depths are reasonable. Ponding is generally contained within the road.

92cm

90cm

85cm

Sameng Inc.

D-33

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 8 â&#x20AC;&#x201C; Country Club Estates How to Reduce Flood Risks? An improvement concept was not developed/modeled for this area. Preventing flooding in this area will be quite challenging given the area has no adequate major drainage overflow. Flood mitigation concepts that may be reviewed include: 1- Improve major drainage overflow path to the southeast. This could be done by converting some of the grassed alleys into swales/ditches southeast of the depressions, all the way to 63 Avenue between 94 and 95 Street, and continuing south to the golf course. 2- Reduce amount of surface drainage getting into this depression, most especially major drainage from the Poplar Drive north of 68 Avenue. This could be done by constructing ditches or small ponds along 68 Avenue near Poplar Drive to control flows. A small pond could also be constructed at the green space north of Poplar Drive and 65 Avenue. 3- Construct/upgrade storm pipe to reduce ponding depths to reasonable levels. These improvement solutions were not modeled.

Sameng Inc.

D-34

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 9 â&#x20AC;&#x201C; Richmond Industrial / College Park (southwest) Main Flood Mechanisms and Flood Risk Areas The Richmond Industrial area is at a very high risk of flooding due to excessive surface water and poor major drainage. Many areas in this very impervious industrial complex are at risk of flooding, especially north of the railroad tracks, as well as along 89 Avenue, west of 108 Street. The southwest corner of College Park also appears to be at risk of flooding.

Topography

108 Street

116 Street

112 Street

100 Avenue / HWY 43

89 Avenue

84 Avenue

Sameng Inc.

D-35

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 9 â&#x20AC;&#x201C; Richmond Industrial / College Park (southwest) Area A (112/113 Street and 95 Avenue): Ponding well in excess of 75cm in depth are anticipated in this area during a 100-year event, and up to 55cm is anticipated at the 95 Avenue and 113 Street bend during a 5-year event. This area is prone to flooding because of the very large major drainage flows (the equivalent of a quarter-section of land) flowing into this depression at a peak flow rate of 4,900 L/s (900 L/s during 5-year event) and continue into the railroad ditches via small ditches/swales (red lines on figure) through the private properties. In the process of overflowing to the railroad ditch, and in the process of flowing east inside the railroad ditch, the ponding depths will be such that many sites and buildings will be flooded. During a 5-year event, there will be some ponding on the street, but the model suggests that there will only be minor flood risks for the businesses, with all of the buildings above the flood line.

112 Street

See Section 8.3.5 for the improvement concept.

113 Street

83cm

102cm 94cm

Sameng Inc.

D-36

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 9 â&#x20AC;&#x201C; Richmond Industrial / College Park (southwest) Area B (108/109 Street and 96 Avenue): Ponding in excess of 50cm in depth is anticipated in this area during a 100-year event with an estimated 110cm at the 108 Street cul-de-sac (48cm during 5-year event). Similar to Area A, this area is prone to flooding because of the very large major drainage flows (the equivalent of about a quarter-section of land) flowing into this area at a peak flow rate of more than 3,700 L/s (800 L/s during 5-year event). Due to topography and the existing railroad to the south and 108 Street to the east which are much higher than the depression, there is no adequate major drainage flow out of the area and the water will flood several properties and buildings and vehicles before 108 Street eventually overflows. During a 5-year event, there will be some ponding on the street, but the model suggests that there will only be minor flood risks for the businesses, with all of the buildings above the flood line. See Section 8.3.5 for the improvement concept.

109 Street

97 Avenue

47cm

73cm

Sameng Inc.

D-37

108 Street

110cm

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 9 â&#x20AC;&#x201C; Richmond Industrial / College Park (southwest) Area C (107 Street and 97 Avenue): A ponding depth of 62cm is anticipated at this intersection during a 100-year event (27cm during 5-year event). Major drainage is to the south through a vacant lot and into the railroad ditch, flowing east. However, the model suggests that there will be flooding in the area due to the large ponding depths, and the large flows and flow depth in the railroad ditch. During a 5-year event, there will be some ponding on the street, but the model suggests that there will only be minor flood risks for the businesses, with all of the buildings above the flood line. According to design documentation for this recent industrial development, each lot must have on-lot control of their stormwater. The model does not include these on-lot control facilities (as they are unknown) and may be overestimating the flood risks in the area.

108 Street

107 Street

See Section 8.3.5 for the improvement concept.

97 Avenue

62cm

60cm

Sameng Inc.

D-38

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 9 â&#x20AC;&#x201C; Richmond Industrial / College Park (southwest) Area D (89 Avenue and 112 Street): Similar to Area A and B, these depressions are at the downstream end of very large catchments area (>50ha). If the sewers cannot convey all the flows, major drainage flows from the area are directed to 89 Avenue, flowing east. Ponding depths between 50cm and 60cm are anticipated at these three depressions (between 30cm and 40cm during 5-year event). A high point on 89 Street just east of 112 Street (where the now-removed railroad spur line used to be) traps some of the water in this area and poses a flood risk to many industrial yards. Along 89 Avenue just east of 112 Street, major drainage flows peak at 4,200 L/s during the 100-year event which is very large (it is only 200 L/s during the 5-year event). Major drainage overflow from Area D makes its way into Area E. During a 5-year event, there will be some ponding on the street, but the model suggests that flood risks are negligible. See Section 8.3.5 for the improvement concept.

58cm

57cm

63cm

Sameng Inc.

D-39

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 9 â&#x20AC;&#x201C; Richmond Industrial / College Park (southwest) Area E (89 Avenue and 108/109 Street): Area E is at the downstream end of Richmond Industrial, both in terms of sewer flows and major drainage flows. It is just upstream of the Canfor Ditch which is the main outlet for storm sewers servicing the Richmond Industrial area. This area is at a very high risk of flooding for a variety of reasons: 1- It is a very large depression at the downstream end of a very large major drainage basin. Surface drainage to the east is blocked by the much higher 108 Street, meaning that all surface flows reaching this depression must enter the sewer system to flow into the Canfor Ditch, or else ponding will happen, and many streets and industrial yards will be flooded. During the 100-year event, water flows into that depression at a peak flow rate of more than 9,500 L/s and the maximum ponding depth will be 155cm on 89 Avenue, just west of 108 Street. During the 5-year event, this area will see a surface flow rate of more than 1,600 L/s and a ponding depth of 98cm at the deepest point. 2- The downstream Canfor ditch is quite shallow, and it has many culverts that restrict the flows. During the 100-year event, the water level in the downstream ditch will be so high that it will be higher than the large depression on 89 Street, as shown in the profile below. 3- Since this depression is much lower than the upstream and downstream pipes, a surcharge in the sewer system may cause flooding at this depression by overflowing into the depressions via manholes and catchbasins. This is the main reason for the flooding during the 5-year event.

Culvert

89 Avenue Canfor Ditch

Outfall

108 Street

Depression

110 Street

4- This area may flood for many hours; in excess of 4 hours during a 100-year event, and for about 3 hours during a 5-year event. This is because the sewer system is very surcharged and cannot convey the surface flows until it regains its capacity.

During the 100-year event, a very large area will be flooded and many industrial yards and buildings will be damaged. Streets will also be impassable, and many vehicles could flood. During a 5-year event, the flooding will also be quite deep, but damages to industrial yard and building should be quite minimal; it would be more of a nuisance.

Sameng Inc.

D-40

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 9 â&#x20AC;&#x201C; Richmond Industrial / College Park (southwest) See Section 8.3.5 for the improvement concept.

92 Avenue

70cm

89cm

110cm

89 Avenue

155cm

41cm

Sameng Inc.

108 Street

109 Street

110 Street

79cm

D-41

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 9 – Richmond Industrial / College Park (southwest) Area F (84 Avenue and 108/109 Street): There are three depressions in this area where ponding depths will exceed 50cm; the deepest being on 84 Avenue west of 108 Street. The area is flooding because major drainage flows from the west along 84 Avenue are trapped at 108 Street which is a bit higher in elevation. As a result, a few buildings and the parking lot at “CENTER 84” are at risk of flooding. The flooded roads will also be impassable for many hours, which may be a concern for emergency vehicles. During a 5-year event, the ponding depths should be less than 35cm and flood risks should be minimal.

109 Street

86 Avenue

108 Street

An improvement concept was not developed/modeled for this area. It is recommended to reduce the overflow elevation of 108 Street to ensure the “CENTER 84” site will not flood.

52cm

72cm

84 Avenue

90cm

Sameng Inc.

D-42

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 10 â&#x20AC;&#x201C; Gateway (south) Main Flood Mechanisms and Flood Risk Areas The commercial developments at the southern end of the Gateway neighbourhood is at risk of flooding due to extreme surcharging in the sewer system on 100 Avenue and 108 Street. These main roads are higher in elevation than the commercial site, meaning that if the sewers are surcharged to ground, water may backflow into the commercial site. Topography in the area slopes towards that commercial development at the northwest corner of 100 Avenue and 108 Street.

108 Street

110 Street

Topography

104 Avenue

A 100 Avenue / HWY 43

Sameng Inc.

D-43

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 10 â&#x20AC;&#x201C; Gateway (south) Area A (Commercial Site at 102 Avenue and 109 Street): Ponding well in excess of 75cm in depth are anticipated in the parking lot of this commercial development during a 100-year event (less than 35cm during 5-year event) posing a flood risk to several vehicles that may be parked in this parking lot during that extreme rainfall event, as well as threatening to flood some of the commercial buildings. Flooding of the parking lot is anticipated to be sustained for close to 4 hours. This area is mostly at risk because of water backflowing from the sewers on 100 Avenue and 108 Street into the commercial site, which is at a lower elevation than the main roads. During a 5-year event, flood risks are negligible.

104 Avenue

80cm

109 Street 100 Avenue / HWY 43

Sameng Inc.

D-44

90cm

108 Street

104cm

110 Street

85cm

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 10 â&#x20AC;&#x201C; Gateway (south) How to Reduce Flood Risks? An improvement concept was not developed/modeled for this area. Some of the flood mitigation concepts for this area are: 1- Reduce peak flows in the 100 Avenue and 108 Street sewers by reducing upstream flow contributions. 2- Increase the pipe size downstream of the commercial site to prevent backflow of the storm trunk into the commercial site. 3- Add underground storage at the commercial site, with flap gate. 4- Add overflow pipe/culvert across 108 Street north of 100 Avenue, and convey the overflows east towards College Park. This pipe could be connected to the commercial site sewers or to the 108 Street main trunk. This may increase flood risks in College Park.

Sameng Inc.

D-45

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 11 â&#x20AC;&#x201C; Northgate (north) / Albinati Industrial Main Flood Mechanisms and Flood Risk Areas This industrial area, which is serviced by ditches, may be at a flood risk during extreme rainfall events. Topography in the area is generally to the south towards the Crystal Lake wetland or south along the east side of the railroad.

97B Street

Topography

132 Avenue (HWY 670)

128 Avenue

Sameng Inc.

D-46

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 11 â&#x20AC;&#x201C; Northgate (north) / Albinati Industrial Area A (97B Street north of 132 Avenue): Modeling results suggest that the area north of 132 Avenue and east of 97B Street may experience some surface flooding during a 100-year event, although most buildings appear to be above the flood levels. The flood risks are associated with a lack of culvert capacity, resulting in overflowing of the culvert crossings and flooding of properties in the process. It should be noted that prior to overflowing 132 Avenue to the south, a large area north of 132 Avenue will be flooded.

97B Street

The property just north of 132 Avenue and west of 97B Street is at a high risk of flooding as the surrounding main roads are higher. This area relies on the culverts being able to convey all peak flows from the area, or else ponding and flooding will result. This area receives runoff from a large catchment area to the north. Major drainage overflow out of this area is east across 97B Street.

132 Avenue (HWY 670)

Sameng Inc.

D-47

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 11 â&#x20AC;&#x201C; Northgate (north) / Albinati Industrial Area B (97B Street south of 132 Avenue): Modeling results suggest that the industrial area south of 132 Avenue may experience some surface flooding during a 100-year event, although most buildings appear to be above the flood levels. The flood risks are associated with a lack of culvert capacity, resulting in overflowing of the culvert crossings and flooding of properties in the process.

97B Street

132 Avenue (HWY 670)

106cm

116 Avenue

Sameng Inc.

D-48

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Location 11 â&#x20AC;&#x201C; Northgate (north) / Albinati Industrial How to Reduce Flood Risks? An improvement concept was not developed/modeled for this area. It is recommended to complete a thorough evaluation of the drainage system and flood risks for the area, including an inventory of existing culverts (condition, size and elevation), and ditches (condition and geometry). To reduce flood risks for the area, culverts may need to be increased in size, and/or stormwater management facilities constructed.

Sameng Inc.

D-49

Storm Drainage Master Plan 2018 Final Report (Revision 1)

Appendix E: Conceptual Cost Estimates

Sameng Inc.

City of Grande Prairie

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table E-1: Summary of Conceptual Cost Estimates Table #

Description

Total

Contingency

Engineering Grand Total Fees

E-2

Highland Park / Swanavon Area

$ 8,653,610

$ 4,327,000

$ 1,298,000

$ 14,278,610

E-3

Northridge Area

$ 14,939,400

$ 7,470,000

$ 2,241,000

$ 24,650,400

E-4

Avondale / Montrose Area

$ 14,073,530

$ 7,037,000

$ 2,111,000

$ 23,221,530

E-5

Ivy Lake / Cobblestone / Smith Area

$ 6,637,640

$ 3,319,000

996,000

$ 10,952,640

E-6a

Richmond Area - Option 1

$ 15,316,970

$ 7,658,000

$ 2,298,000

$ 25,272,970

E-6b

Richmond Area - Option 2

$ 16,718,030

$ 8,359,000

$ 2,508,000

$ 27,585,030

E-6c

Richmond Area - Option 3

$ 15,338,790

$ 7,669,000

$ 2,301,000

$ 25,308,790

E-6d

Richmond Area - Option 4

$ 15,937,430

$ 7,969,000

$ 2,391,000

$ 26,297,430

Sameng Inc.

E-1

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table E-2: Conceptual Cost Estimate for Highland / Swanavon Area Item

Description

Quantity

Unit

L.S.

Unit Price

Cost

1 General Requirements 1.1 Mobilization, Demobilization and General Requirements

$ 865,000 $

865,000

Subtotal Item

Description

Quantity

Unit

2.1 Existing Road Structure Removal

8147

2.2 Install 1200mm Storm Pipe along 94 Ave

410

l.m.

3,950

$ 1,619,500

2.3 Install 1500mm Storm Pipe along 100 Street

250

l.m.

4,220

$ 1,055,000

2.4 Install 1800mm Storm Pipe along 94 Ave and 99 Street

$ 3,895,800

Unit Price

Cost

2 Storm Pipe Installation 20 $

162,940

860

l.m.

4,530

2.5 Connection to Existing Pipe (600mm)

L.S.

8,400

33,600

2.6 Connection to Existing Pipe (900mm)

L.S.

9,950

2.7 Storm Outfall for 1800mm Pipe

L.S.

$ 178,000 $

178,000

2.8 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

345,000

488,820

2.9 Road Structure Restoration

8147

60 $

Subtotal Item

$ 7,788,610 Description

Quantity

Unit

Unit Price

Cost

3 Modification to Existing System (Optional 1) 3.1 Interconnection to Existing 300mm Pipe

l.m.

560

30,800

3.2 Abandon Existing Outfall

L.S.

8,500

39,300

Subtotal Item

Description

Quantity

Unit

Unit Price

Cost

4 Modification to Existing System (Optional 2) 4.1 Interconnection to Existing 750mm Pipe

l.m.

1,380 $

4.2 Abandon Existing Outfall

L.S.

8,500

Subtotal Total (excluding Alternatives and Optional Items)

117,300

8,500

125,800

$ 8,653,610

Contingency

50%

$ 4,327,000

Engineering Fee

15%

$ 1,298,000

Grand Total

$ 14,278,610

Sameng Inc.

E-2

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table E-3: Conceptual Cost Estimate for Northridge Area Item

Description

Quantity

Unit

Unit Price

L.S.

$ 1,494,000

Cost

1 General Requirements 1.1 Mobilization, Demobilization and General Requirements Subtotal Item

$ 1,494,000 $ 1,494,000

Description

Quantity

Unit

2380

47,600 177,750

Unit Price

Cost

2 Storm Pipe Installation (along 116 Ave between 98 and 100 ST) 2.1 Existing Road Structure Removal 2.2 Install 1200mm Storm Pipe and Connect to Pipe on 98 Street

l.m.

3,950 $

400

l.m.

4,530

2.4 Connection to Existing Pipe (1200mm)

L.S.

11,500

2.5 Storm Inlet for 1800mm Pipe

L.S.

$ 178,000 $

178,000

2.6 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

230,000

2.7 Road Structure Restoration

2380

60 $

142,800

2.8 Road Intersection Regrading

1000

45,000

2.9 Remove Existing Culvert

L.S.

5,000

2.1 Berm Construction

l.m.

720

2.3 Install 1800mm Storm Pipe along 116 Avenue

Subtotal Item

$ 1,812,000

$ 2,650,370 Description

Quantity

Unit

22000

Unit Price

Cost

3 Ditch Deepening and Widening (along 116 Ave) 3.1 Deepen and Widen Existing Ditch at South of 116 Ave

12 $

518

10,360

3.3 Install 900mm Storm Pipe

l.m.

2,750

13,750

3.4 Install 1500mm Storm Pipe at West of 100 Street

l.m.

4,220

84,400

3.5 Replace Existing 1500m Pipe with 2100mm Pipe

l.m.

5,150 $

154,500

3.6 Install 2100mm Storm Pipe at West of 101 Street

l.m.

5,150 $

154,500

3.7 Install 2100mm Culvert at 102 Street

l.m.

4,120 $

206,000

265

l.m.

6,230

$ 1,650,950

3.9 Connection to Existing Pipe (900mm)

L.S.

9,950

9,950 13,200

3.2 Existing Road Structure Removal (116 Ave)

3.8 Install 2700mm Storm Pipe fron 106 Ave to Bear Creek

264,000

3.1 Connection to Existing Pipe (1500mm)

L.S.

13,200

3.11 Connection to Existing Pipe (2100mm)

L.S.

15,300

3.12 Storm Outfall for 1500mm Pipe

L.S.

$ 145,000 $

145,000

3.13 Storm Outfall for 2100mm Pipe

L.S.

$ 235,800 $

235,800

3.14 Storm Inlet for 2700mm Pipe

L.S.

$ 264,300 $

264,300

3.15 Storm Outfall for 2700mm Pipe

L.S.

$ 264,300 $

264,300

3.16 Road Structure Restoration

518

31,080

3.17 Road Intersection Regrading

500

22,500

Subtotal

$ 3,539,890

Sameng Inc.

E-3

Storm Drainage Master Plan 2018 Final Report (Revision 1) Item

City of Grande Prairie

Description

Quantity

Unit

4.1 Existing Road Structure Removal

7243

20 $

144,860

4.2 Install 1200mm Storm Pipe on Royal Oaks Drive

140

l.m.

3,950 $

553,000

4.3 Install 1500mm Storm Pipe

630

l.m.

4,220

$ 2,658,600

4.4 Install 2100mm Storm Pipe along 102 Street

510

l.m.

5,150

$ 2,626,500

4.5 Connection to Existing Pipe (1200mm)

L.S.

11,500

4.6 Connection to Existing Pipe (2100mm)

L.S.

15,300

4.7 Storm Outfall for 2100mm Pipe

L.S.

$ 235,800 $

235,800

4.8 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

575,000

434,580

Unit Price

Cost

4 Storm Pipe Installation (along 102 Street)

4.9 Road Structure Restoration

7243

60 $

Subtotal Item

11,500

$ 7,255,140 Description

Quantity

Unit

11400

l.m.

Unit Price

Cost

5 Ditch Deepening and Widening (Alternative to ITEM 4) 5.1 Deepen and Widen Existing Ditch along 101 Street 5.2 Install 1600mm Culvert

12 $ 2,830

Subtotal Total (excluding Alternatives and Optional Items)

136,800

84,900

221,700

$ 14,939,400

Contingency

50%

$ 7,470,000

Engineering Fee

15%

$ 2,241,000

Grand Total

$ 24,650,400

Sameng Inc.

E-4

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table E-4: Conceptual Cost Estimate for Avondale / Montrose Area Item

Description

Quantity

Unit

Unit Price

L.S.

$ 1,407,000

Cost

1 General Requirements 1.1 Mobilization, Demobilization and General Requirements Subtotal Item

$ 1,407,000 $ 1,407,000

Description

Quantity

Unit

Unit Price

Cost

2 Storm Pipe Installation (along 108 Ave turn South at 103 Street and Discharge to Bear Creek) 2.1 Existing Road Structure Removal

8274

2.2 Install 1500mm Storm Pipe

370

l.m.

4,220

2.3 Install 1800mm Storm Pipe along 108 Avenue

190

l.m.

4,530 $

2.4 Install 2100mm Storm Pipe

860

l.m.

5,150

20 $

165,480

$ 1,561,400 860,700

$ 4,429,000

2.5 Upgrade Existing 525mm Pipe to 900mm Pipe

l.m.

2,750 $

2.6 Connection to Existing Pipe (750mm)

L.S.

9,100

2.7 Connection to Existing Pipe (900mm)

L.S.

9,950

49,750

2.8 Connection to Existing Pipe (1050mm)

L.S.

10,300

2.9 Upgrade Storm Outlet for 2400mm Pipe

L.S.

$ 256,300 $

256,300

2.1 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

690,000

60 $

496,440

45 $

176,400

2.11 Road Structure Restoration

8274

2.12 Road Intersection Regrading

3920

Subtotal Item

110,000

$ 8,814,870 Description

Quantity

Unit

3.1 Deepen and Widen Existing Ditch (between 112 Ave to 110 Ave)

1800

54,000

3.2 Reinstall Walkway

150

l.m.

220

33,000

3.3 Walkway Side Landscaping

450

7,200

3.4 Deepen and Widen Existing Ditch (in the Open Field)

3000

36,000

3.5 Ditch and Park Landscaping

3000

3.6 Road Intersection Regrading

10660

Unit Price

Cost

3 Ditch Deepening and Widening (along 103 Street)

Subtotal

Sameng Inc.

E-5

24,000

45 $

479,700

633,900

Storm Drainage Master Plan 2018 Final Report (Revision 1) Item

City of Grande Prairie

Description

Quantity

Unit

4.1 Existing Walkway Removal

165

3,300

4.2 Upgrade Existing pipe to 900mm Pipe (between 112 Ave to 110 Ave)

195

l.m.

2,750 $

536,250

4.3 Upgrade Existing pipe to 900mm Pipe (in the Open Field)

200

l.m.

1,925 $

385,000

4.4 Reinstall Walkway

150

l.m.

220

33,000

4.5 Walkway Side Landscaping

450

7,200

8,000

45 $

479,700

Unit Price

Cost

4 Storm Pipe Installation (along103 Street, Alternative 1)

4.6 Ditch and Park Landscaping

1000

4.7 Road Intersection Regrading

10660

Subtotal Item

$ 1,452,450 Description

Quantity

Unit

Unit Price

Cost

5 Storm Pipe Installation (along 97 Street and Turn West at 108 Ave) 5.1 Existing Road Structure Removal

3647

5.2 Install 1050mm Storm Pipe

370

l.m.

3,620

$ 1,339,400

5.3 Install 1500mm Storm Pipe along (96A Street and 108 Avenue)

72,940

320

l.m.

4,220

$ 1,350,400

5.4 Connection to Existing Pipe (525mm)

L.S.

6,200

5.5 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

230,000

3647

218,820

5.6 Road Structure Restoration

60 $

Subtotal Item

$ 3,217,760 Description

Quantity

Unit

Unit Price

6.1 Install 1200mm Pond Overflow Pipe (Trenchless Pipe Installation)

l.m.

5,500 $

6.2 Install 1200mm Pond Overflow Pipe (Open Cut)

l.m.

3,950

59,250

6.3 Install 1200mm Pipe Inlet

L.S.

$ 123,000 $

123,000

6.4 Proposed Large Diameter Outlet with Grate

L.S.

$ 115,000 $

115,000

544,750

Cost

6 Pond Overflow Pipe (Across Railroad, Alternative 2)

Subtotal

Total (excluding Alternatives and Optional Items)

247,500

$ 14,073,530

Contingency

50%

$ 7,037,000

Engineering Fee

15%

$ 2,111,000

Grand Total

$ 23,221,530

Sameng Inc.

E-6

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table E-5: Conceptual Cost Estimate for Ivy Lake / Cobblestone / Smith Area Item

Description

Quantity

Unit

L.S.

Unit Price

Cost

1 General Requirements 1.1 Mobilization, Demobilization and General Requirements

$ 664,000 $

664,000

Subtotal Item

Description

Quantity

Unit

Unit Price

Cost

2 Storm Pipe Installation (along 100 Ave to Pond at North of 100 Ave) 2.1 Existing Road Structure Removal

2135

2.2 Install 2100mm Storm Pipe

450

l.m.

5,150

2.3 Storm Outlet for 2100mm Pipe

L.S.

$ 235,800 $

2.4 Connection to Existing Pipe (1200mm)

L.S.

$ 11,500

11,500

2.5 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

115,000

2135

60 $

128,100

15000

45 $

675,000

l.m.

2.6 Road Structure Restoration 2.7 Road Intersection Regrading 2.8 Berm Construction Subtotal Item

42,700

$ 2,317,500

235,800

1,440

$ 3,527,040 Description

Quantity

Unit

48500

12 $

582,000

3.2 Install 1500mm Culvert along 92 Ave

l.m.

2,460 $

147,600

3.3 Install 1500mm Culvert at East of Railway Track (2 in Total)

l.m.

2,460 $

196,800

150

l.m.

2,460 $

369,000

48500

8 $

388,000

Unit Price

Cost

3 Ditch Deepening and Widening (around Railway Industrial) 3.1 Deepen and Widen Existing Ditch around Railway Industrial

3.4 Install 1500mm Culvert along 92 Street (5 in Total) 3.5 Ditch Area Landscaping Subtotal Item

$ 1,683,400 Description

Quantity

Unit

Unit Price

Cost

4 Regrading Surface for Major Drainge Modification (In Smith and Morgan Meadows Area) 4.1 Road Intersection Regrading

16960

45 $

763,200

Subtotal

763,200

Total (excluding Alternatives and Optional Items)

$ 6,637,640

Contingency

50%

$ 3,319,000

Engineering Fee

15%

Grand Total

996,000

$ 10,952,640

Sameng Inc.

E-7

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table E-6a: Conceptual Cost Estimate for Richmond Area â&#x20AC;&#x201C; Option 1 Item

Description

Quantity

Unit

Unit Price

L.S.

$ 1,532,000

Cost

1 General Requirements 1.1 Mobilization, Demobilization and General Requirements Subtotal Item

Description

1,532,000

Quantity

Unit

Unit Price

Cost

36000

12 $

432,000

6400

25 $

160,000

2.3 Install 1500mm Storm Culvert

l.m.

2,460

86,100

2.4 Install 2100mm Storm Culvert

l.m.

4,120 $

123,600

2.5 Install 1200mm Pipe to 84 Ave

3,950 $

553,000

2 Proposed Richmond Storm Pond 2.1 Construction and Upgrade of Proposed Richmond Pond 2.2 Remove Existing Parking Lots and Fences

140

l.m.

2.6 Connect to Existing Pipe (1200mm)

L.S.

11,500

2.7 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

115,000

1,481,200

11,500

Subtotal Item

Description

Quantity

Unit

Unit Price

Cost

3.1 Deepen and Widen Existing Ditch at Both side of Railroad

28700

12 $

344,400

3.2 Construction of Dry Pond at West of 108 Street

17000

12 $

204,000

3.3 Install 1200mm Storm Pipe at West of Dry Pond

l.m.

3,950 $

158,000

3.4 Install 1500mm Storm Pipe at East of Dry Pond

l.m.

4,220 $

3.5 Replace Existing XXmm Pipe with 1500mm Pipe

260

l.m.

4,220

1,097,200

3 Proposed Ditch Upgrating along Railroad

211,000

3.6 Install 600mm Culvert at 108 Street (2 in Total)

l.m.

1,060

84,800

3.7 Connection to Existing Pipe (600mm)

L.S.

8,400

16,800

3.8 Connection to Existing Pipe (1200mm)

L.S.

11,500

3.9 Connection to Existing Pipe (1500mm)

L.S.

13,200

3.1 Storm Pond Inlet for 1200mm Pipe

L.S.

$ 123,000 $

123,000

3.11 Storm Pond Inlet for 1500mm Pipe

L.S.

$ 145,000 $

145,000

3.12 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

115,000

3.13 Berm Construction

465

l.m.

33,480

3.14 Overflow Improvement (Surface Regrading)

3600

30 $

108,000

2,665,380

Subtotal Item

Description

Quantity

Unit

Unit Price

Cost

4.1 Existing Road Structure Removal

1098

21,960

4.2 Upgrade 1500mm Pipe to 2100mm Storm Pipe

180

l.m.

5,150 $

927,000

4.3 Upgrade 1050mm Pipe to 2400mm Storm Pipe

220

l.m.

5,720

1,258,400

4.4 Upgrade Culvert to 3m Span + 2.4m Rise Box Culvert

945

l.m.

7,150

6,756,750

4.5 Storm Outfall for 2400mm Pipe

L.S.

$ 256,300 $

256,300

4.6 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

230,000

1098

4 Proposed Large Diameter Storm Pipe Upgrading

4.7 Road Structure Restoration

Subtotal Item

Description

Quantity

Unit

65,880

9,516,290

Unit Price

Cost

5 Ditch Deepening and Widening (along Railraod East of 108 Street) 5.1 Deepen and Widen Existing Ditch East of 108 Street

6350

5.2 Overflow Improvement (Surface Regrading)

1530

45,900

122,100

Subtotal Total (excluding Alternatives and Optional Items)

76,200

$ 15,316,970

Contingency

50%

7,658,000

Engineering Fee

15%

2,298,000

Grand Total

$ 25,272,970

Sameng Inc.

E-8

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table E-6b: Conceptual Cost Estimate for Richmond Area â&#x20AC;&#x201C; Option 2 Item

Description

Quantity

Unit

Unit Price

L.S.

$ 1,672,000

Cost

1 General Requirements 1.1 Mobilization, Demobilization and General Requirements Subtotal Item

$ 1,672,000 $ 1,672,000

Description

Quantity

Unit

Unit Price

Cost

36000

12 $

432,000

6400

25 $

160,000

2.3 Install 1500mm Storm Culvert

l.m.

2,460

86,100

2.4 Install 2100mm Storm Culvert

l.m.

4,120 $

123,600

2.5 Install 1200mm Pipe to 84 Ave

3,950 $

553,000

2 Proposed Richmond Storm Pond 2.1 Construction and Upgrade of Proposed Richmond Pond 2.2 Remove Existing Parking Lots and Fences

140

l.m.

2.6 Connect to Existing Pipe (1200mm)

L.S.

11,500

2.7 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

115,000

11,500

Subtotal Item

$ 1,481,200 Description

Quantity

Unit

Unit Price

Cost

3 Proposed Ditch Upgrating along Railroad 25830

12 $

3.2 Existing Road Structure Removal

1769

35,380

3.3 Install 1200mm Storm Pipe along Railroad

170

l.m.

3,950 $

671,500

3.4 Install 2100mm Storm Pipe along 108 Street

290

l.m.

5,150

$ 1,493,500

3.5 Replace Existing XXmm Pipe with 1500mm Pipe

260

l.m.

4,220

$ 1,097,200

3.6 Install 600mm Culvert at 108 Street

l.m.

1,060

42,400

3.7 Connection to Existing Pipe (600mm)

L.S.

8,400

16,800

3.8 Connection to Existing Pipe (1200mm)

L.S.

11,500

3.9 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

115,000

350

l.m.

25,200

3600

30 $

108,000

3.1 Deepen and Widen Existing Ditch at Both side of Railroad

3.1 Berm Construction 3.11 Overflow Improvement (Surface Regrading) Subtotal Item

309,960

$ 3,926,440 Description

Quantity

Unit

Unit Price

Cost

4.1 Existing Road Structure Removal

1098

21,960

4.2 Upgrade 1500mm Pipe to 2100mm Storm Pipe

180

l.m.

5,150 $

927,000

4.3 Upgrade 1050mm Pipe to 2400mm Storm Pipe

220

l.m.

5,720

$ 1,258,400

4.4 Upgrade Culvert to 4.8m Span + 2.4m Rise Box Culvert

945

l.m.

7,150

$ 6,756,750

4.5 Storm Outfall for 2400mm Pipe

L.S.

$ 256,300 $

256,300

4.6 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

230,000

1098

4 Proposed Large Diameter Storm Pipe Upgrading

4.7 Road Structure Restoration

Subtotal Item

65,880

$ 9,516,290 Description

Quantity

Unit

Unit Price

Cost

5 Ditch Deepening and Widening (along Railraod East of 108 Street) 5.1 Deepen and Widen Existing Ditch East of 108 Street

6350

5.2 Overflow Improvement (Surface Regrading)

1530

45,900

122,100

Subtotal Total (excluding Alternatives and Optional Items)

76,200

$ 16,718,030

Contingency

50%

$ 8,359,000

Engineering Fee

15%

$ 2,508,000

Grand Total

$ 27,585,030

Sameng Inc.

E-9

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table E-6c: Conceptual Cost Estimate for Richmond Area â&#x20AC;&#x201C; Option 3 Item

Description

Quantity

Unit

Unit Price

L.S.

$ 1,534,000

Cost

1 General Requirements 1.1 Mobilization, Demobilization and General Requirements Subtotal Item

$ 1,534,000 $ 1,534,000

Description

Quantity

Unit

Unit Price

Cost

2.1 Construction and Upgrade of Proposed Richmond Pond

54900

12 $

658,800

2.2 Remove Existing Parking Lots and Fences

12700

25 $

317,500

2.3 Install 1500mm Storm Culvert

l.m.

2,460

86,100

2.4 Install 2100mm Storm Culvert

l.m.

4,120 $

123,600

2.5 Install 1200mm Pipe to 84 Ave

3,950 $

553,000

2 Proposed Richmond Storm Pond

140

l.m.

2.6 Connect to Existing Pipe (1200mm)

L.S.

11,500

2.7 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

230,000

3600

108,000

2.8 Overflow Improvement (Surface Regrading)

11,500

30 $

Subtotal Item

$ 2,088,500 Description

Quantity

Unit

Unit Price

Cost

3.1 Construction of Dry Pond at West of 108 Street

17000

12 $

204,000

3.2 Install 1200mm Storm Pipe at West of Dry Pond

l.m.

3,950 $

158,000

3.3 Install 1500mm Storm Pipe at East of Dry Pond

l.m.

4,220 $

211,000

3.4 Replace Existing XXmm Pipe with 1500mm Pipe

260

l.m.

4,220

3.5 Connection to Existing Pipe (1200mm)

L.S.

11,500

3.6 Connection to Existing Pipe (1500mm)

L.S.

13,200

3.7 Storm Pond Inlet for 1200mm Pipe

L.S.

$ 123,000 $

123,000

3.8 Storm Pond Inlet for 1500mm Pipe

L.S.

$ 145,000 $

145,000

3.9 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

115,000

3 Proposed Dry Pond at West of 108 Street

Subtotal Item

$ 1,097,200 11,500

$ 2,077,900 Description

Quantity

Unit

Unit Price

Cost

4 Proposed Storm Large Diameter Storm Pipe Upgrading 4.1 Existing Road Structure Removal

1098

21,960

4.2 Upgrade 1500mm Pipe to 2100mm Storm Pipe

180

l.m.

5,150 $

927,000

4.3 Upgrade 1050mm Pipe to 2400mm Storm Pipe

220

l.m.

5,720

$ 1,258,400

4.4 Upgrade Culvert to 4.8m Span + 2.4m Rise Box Culvert

945

l.m.

7,150

$ 6,756,750

4.5 Storm Outfall for 2400mm Pipe

L.S.

$ 256,300 $

256,300

4.6 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

230,000

1098

4.7 Road Structure Restoration

Subtotal Item

65,880

$ 9,516,290 Description

Quantity

Unit

Unit Price

Cost

5 Ditch Deepening and Widening (along Railraod East of 108 Street) 5.1 Deepen and Widen Existing Ditch East of 108 Street

6350

5.2 Overflow Improvement (Surface Regrading)

1530

45,900

122,100

Subtotal Total (excluding Alternatives and Optional Items)

76,200

$ 15,338,790

Contingency

50%

$ 7,669,000

Engineering Fee

15%

$ 2,301,000

Grand Total

$ 25,308,790

Sameng Inc.

E-10

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Table E-6d: Conceptual Cost Estimate for Richmond Area â&#x20AC;&#x201C; Option 4 Item

Description

Quantity

Unit

Unit Price

L.S.

$ 1,594,000

Cost

1 General Requirements 1.1 Mobilization, Demobilization and General Requirements Subtotal Item

$ 1,594,000 $ 1,594,000

Description

Quantity

Unit

Unit Price

Cost

2 Proposed Richmond Storm Pond 36000

12 $

2.2 Deepen and Widen Existing Ditch at North of Railroad

1550

18,600

2.3 Remove Existing Parking Lots and Fences

6400

25 $

160,000

2.4 Install 1500mm Storm Culvert

l.m.

2,460

86,100

2.5 Install 2100mm Storm Culvert

l.m.

4,120 $

123,600

2.6 Install 1200mm Pipe to 84 Ave

3,950 $

553,000

2.1 Construction and Upgrade of Proposed Richmond Pond

432,000

140

l.m.

2.7 Connect to Existing Pipe (1200mm)

L.S.

11,500

2.8 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

230,000

3600

108,000

2.9 Overflow Improvement (Surface Regrading)

11,500

30 $

Subtotal Item

$ 1,722,800 Description

Quantity

Unit

Unit Price

Cost

3 Proposed Dry Pond at West of 108 Street 3.1 Construction of Dry Pond at West of 108 Street

17000

12 $

204,000

3.2 Install 1200mm Storm Pipe at West of Dry Pond

l.m.

3,950 $

158,000

3.3 Install 1500mm Storm Pipe at East of Dry Pond

l.m.

4,220 $

211,000

170

l.m.

3,950 $

671,500

3.5 Connection to Existing Pipe (1200mm)

L.S.

11,500

3.6 Storm Pond Inlet for 1200mm Pipe

L.S.

$ 123,000 $

123,000

3.7 Storm Pond Inlet for 1500mm Pipe

L.S.

$ 145,000 $

145,000

3.8 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

115,000

3.4 Install 1200mm Storm Pipe along 108 Street

11,500

Subtotal Item

$ 1,639,000 Description

Quantity

Unit

Unit Price

Cost

4 Proposed Storm Pipe Installation (along 92 Ave) 4.1 Existing Road Structure Removal

1482

4.2 Install 300mm Storm Pipe

140

l.m.

560

78,400

4.3 Install 1500mm Storm Pipe

160

l.m.

4,220 $

675,200

5,150 $

309,000

29,640

4.4 Install 2100mm Storm Pipe (Trenchless Installation)

l.m.

4.5 Install Weir

L.S.

13,000

4.6 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

230,000

4.7 Move Orifice

L.S.

13,000 8,000

Subtotal Item

8,000

$ 1,343,240 Description

Quantity

Unit

Unit Price

Cost

5 Proposed Storm Large Diameter Storm Pipe Upgrading 5.1 Existing Road Structure Removal

1098

21,960

5.2 Upgrade 1500mm Pipe to 2100mm Storm Pipe

180

l.m.

5,150 $

927,000

5.3 Upgrade 1050mm Pipe to 2400mm Storm Pipe

220

l.m.

5,720

$ 1,258,400

5.4 Upgrade Culvert to 4.8m Span + 2.4m Rise Box Culvert

945

l.m.

7,150

$ 6,756,750

5.5 Storm Outfall for 2400mm Pipe

L.S.

$ 256,300 $

256,300

5.6 Proposed Large Diameter Catchbasin Inlet with Grate

L.S.

$ 115,000 $

230,000

1098

5.7 Road Structure Restoration

Subtotal Item

65,880

$ 9,516,290 Description

Quantity

Unit

Unit Price

Cost

6 Ditch Deepening and Widening (along Railraod East of 108 Street) 6.1 Deepen and Widen Existing Ditch East of 108 Street

6350

6.2 Overflow Improvement (Surface Regrading)

1530

45,900

122,100

Subtotal Total (excluding Alternatives and Optional Items)

76,200

$ 15,937,430

Contingency

50%

$ 7,969,000

Engineering Fee

15%

$ 2,391,000

Grand Total

$ 26,297,430

Sameng Inc.

E-11

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Appendix F: Stakeholder Open House Summary Report â&#x20AC;&#x201C; May 9, 2018

Sameng Inc.

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) â&#x20AC;&#x201C; May 9, 2018

City of Grande Prairie

Stakeholder Open House Report (Revision 1) May 9, 2018 Table of Contents Table of Contents .................................................................................................................... i List of Appendices ................................................................................................................... i 1.0

Summary Information ................................................................................................... 1

2.0

Notification and Attendance .......................................................................................... 2

3.0

Session Details............................................................................................................. 3

4.0

Participant Feedback .................................................................................................... 4

List of Appendices Appendix A: Information Slides Appendix B: Display Boards Appendix C: Sign-in Form Appendix D: Feedback Forms

Sameng Inc.

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) – May 9, 2018

1.0

City of Grande Prairie

Summary Information Type

Stakeholder Open House (45-minute presentation and question period followed by walk-around at display boards) •

Objectives

• • •

Share information on the Concept for Stormwater Servicing Present the overall storm sewer system upgrades proposal Present benefits of the approach Answer stakeholder questions and concerns

Date

Wednesday, May 9, 2018

Time

1:30 pm to 4:00 pm

Location

City Services Centre Meeting Room 9505 112 Avenue

Number of Attendees

24 (excluding City Engineering and Consultant employees)

City of Grande Prairie Engineering Services

Richard Sali, Project Manager Jennifer Comeau Mike Harvard

Sameng Inc. (Consultant)

David Yue, Project Manager Nathan Forsyth

Summary for Distribution .

Sameng Inc.

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) â&#x20AC;&#x201C; May 9, 2018

2.0

City of Grande Prairie

Notification and Attendance

An invitation was sent to City departments, active developers, and their consultants. Approximately 40 responses were received. The following attendees were recorded. The total attendance was 24, not counting the project team.

City of Grande Prairie Project Team Sameng Inc. (Consultant)

Richard Sali, Project Manager Jennifer Comeau Mike Harvard David Yue, Project Manager Nathan Forsyth

City of Grande Prairie Staff; City Permiting, Transportation, Energy Management, Planning and Development, GIS.

Beairsto & Associates Engineering (BASE) Helix Engineering

Kayla Klava Cameron Thompson Allison Downing Conor Coney Waleed Albakry Brennan Jones Stuart Wraight Daniel Dawson Robert Carroll Mark Hoseasson Michelle Gairdner Monty Haughian Ashley Colter Kristine Donnelly ReaAnne Leach Dennis Hossey Scott Roessler

Devco Developments Corp. AquaTerra

Bob Leslie Brad Vall

Alberta Environment and Parks

James Proudfoot

Sameng Inc.

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) â&#x20AC;&#x201C; May 9, 2018

3.0

City of Grande Prairie

Session Details

The course of the public information session and information presented/provided is summarized as follows: 1. At their arrival, attendees were greeted and asked to provide their name, company, and email address on a sign-in sheet. The sign-in sheets were kept by the City for a record of people interested in staying apprised of the development of the Master Plan. The sheets are included under Appendix B. 2. The stakeholder open house started with a 40-minute project presentation. A copy of the slides of this presentation are attached in Appendix A. 3. At the end of the presentation, attendees were given the opportunity to ask questions about the presentation and project itself. A summary of the questions and answers is presented in Section 4.0 below. 4. Large display boards were set-up for attendees to look at to allow for easier viewing. Representatives of Sameng and the City were nearby to answer questions. The display boards can be found under Appendix B 5. Attendees were asked to fill out exit questionnaires which solicited their input on additional questions and concerns, and any recommendations or comments they might have on the project. The completed versions can be found in Appendix D. The results are summarized in Section 4.0.

Sameng Inc.

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) â&#x20AC;&#x201C; May 9, 2018

4.0

City of Grande Prairie

Participant Feedback

Question and Answer Period People who attended the open house were generally positive about the project. The questions/concerns that were fielded from attendees during the Question and Answer period and the responses given are summarized below: Q: With the recent flooding, which was brought on by the spring runoff, should we be considering design requirements for an event that reflects the spring runoff event? A: In rural settings the melt runoff is often the critical event. Inside the City, this is less of a concern than the rainfall. Q: If areas in the northwest, northeast, and southwest are being developed to a rural standard. should we require a meltwater be designed for? A: For a purely rural standard, with ditches and culverts, then designing for spring runoff would be appropriate. Q: Will the flood risk maps you are generating be for a 100-year event, or some other event? A: Flood maps will be for a 100-year event. Q: Are we recommending changes to the 100-year event being used for the standard? A: We have recommended updates to the design storm events with a higher peak, although the total volumes in the event arenâ&#x20AC;&#x2122;t changing significantly. Recent studies have shown that burst storms are more of a concern than previously thought. In Edmonton, the 100-year event increased by 50% in volume, as well as an increase in peak. This came after an increased scrutiny on rainfall patterns in the City. We are not proposing those changes here; as there is not enough rainfall data to defend such a change. We are recommending additional monitoring. Q: For the Hughes Lake area, are we recommending pipes, there seems to be a lot of natural areas? A: The Hughes Lake area will rely on the natural storage. The piped system is proposed north of 43X.

Sameng Inc.

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) â&#x20AC;&#x201C; May 9, 2018

City of Grande Prairie

Q: What are the design criteria for forebays? A: We need to at least meet AENV standards and guidelines, there are other considerations in terms of maintenance, bypass, flexibility, etc. Q: It sounds like there is more work to be done on the implementation. Will there be more opportunity for feedback? A: We will have another open house, implementation will be a different scope. Q: Alberta Environment may be concerned with increasing water to wetlands, and you mentioned depths of 0.5 to 1 metres. How will this translate to differences in depth to wetlands? A: The depths given are for the fluctuations during the severe events at the peak. The idea is to avoid altering the natural behavior of the wetland as much as possible. Q: Follow-up. Alberta Environment doesnâ&#x20AC;&#x2122;t generally like to see nests flooded. A: The idea is to avoid changing the natural behavior of the wetlands too much. Normally there should be minimal design change. Q: How will the Stormwater Master Plan affect Inflow and Infiltration in the Sanitary system? A: That is a separate question that would need to be resolved. We have observed in other places that street flood does cause a dramatic increase in I/I. Q: Follow up - Would we look at those impacts? A: If asked to. It is not currently part of the scope of this plan. Q: Will this Master Plan cover/impact infill developments? A: Infill developments would generally expect to rely on existing systems, and we are recommending improvements to fix deficiencies. For greenfield development, there are recommendations that are included. Q: Would the model be able to incorporate future development? A: The model is expandable. Feedback Forms Summary Copies of the completed feedback forms can be found in Appendix D. Sameng Inc.

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) â&#x20AC;&#x201C; May 9, 2018

Appendix A: Information Slides

Sameng Inc.

City of Grande Prairie

City of Grande Prairie Storm Drainage Master Plan

Stakeholder Open House May 9, 2018

Introductions and Purpose of Attendance

Overview of Presentation Purpose: 1. To present findings and recommendations of the City of Grande Prairie’s stormwater drainage master plan. 2. To obtain early feed-back on recommendations.  Overview of the stormwater management infrastructure  Result of Design Standards Review  Design Rainfall Change Recommendation  Wet Storm Pond Control Structure Recommendation  Revisions to future stormwater retention configuration

 Overview of future development’s stormwater management

layout

City of Grande Prairie Overall Map at 2018 Area within City Boundary = 13,658 ha Developed Area = 5,559 ha ER, River Valley, Lakes = 1,317 ha Area to be Developed = 6,782 ha

City of Grande Prairie - Pipe Age Oldest infrastructure dates back to the 1940’s Original town site just south of Bear Reservoir on Bear Creek Growth Period – 1970’s, 2000’s

Existing Outfalls and Network Basins

96 Storm Outfalls (not including outfall into SWMFâ&#x20AC;&#x2122;s) Vary in size from 300mm to 1800mm

Stormwater Management Facilities 43 SWMFs Wet Ponds

Dry Ponds

Forebays

Findings of Existing System  Strengths:

 Many outfalls created independent pipe systems.  Newer developments have positive major and minor

drainage and are therefore more flood resilient.

 Weakness:

 Older areas do not have continuous overland drainage

and depend on pipes to evacuate the runoff.  Pipes are generally small.  In many areas, surface drainage of new development drains through older areas even though the pipes drain separately.

 Options to address the Existing System’s deficiencies

are on-going.

Comments on Moving Forward  Of the total remaining land to be developed, only a small

portion will tie into the existing system. Provisions have been made to accommodate these.  Topography of Grande Prairie suggest that creating positive and continuous surface drainage of land is possible. This should be encouraged as a way to improve flood resiliency.  We have been building at least one storm pond every year for 3 decades. We have more than 43 ponds for a City of 65,000. Given that we need to preserve natural areas also, is this still the best approach?  Majority of the future developments will discharge into lakes and creeks independent of the existing system. Does it make sense to continue to use current design criteria for these developments?

Existing Development Concept

117 Stormwater Management Ponds (16 already build) Total volume of man made storage = 4.7 million m3 Area dedicated to pond storage = 519 ha. Additional ESA preservation area = 588 ha. (not including Bear Creek)

Traditional Design Concept

Topography and Major Basins

Natural Drainage Design Concepts Focus: - Positive, regulated conveyance of runoff to naturally low areas (ESA’s) - Design to improve water quality Scenario 1: Adjacent to ESA’s - Pipe sizing for 5 year event to a water quality forebay. - Major Drainage to forebay. - Forebay sizing to maintain predevelopment discharge rate. - Water quality design for common rainfall; i.e. 2 year. Scneario 2: Longer distance to ESA’s - Pipe sizing for 5 year flow - Storm pond sized to 25 year event to manage basin to basin discharge. - Continuous major and minor drainage to ESA’s/Forebay.

Results of Natural Drainage Design  Preservation of Natural Areas 588 ha creating 2.4 million

cubic meters of storage.  55 Ponds (wet and dry) occupying 190 ha creating 1.7 million cubic meters of storage.  18 Forebays occupying 19 ha and providing 170K cubic meters of storage.  Making use of storage naturally available in 5 lakes (3.2 million cubic meters of storage)  Bear Lake – 3100 ha open water (58 ha development)  Hermit Lake – 194 ha open water (80 ha development)  Flyingshot Lake – 294 ha open water (1000 ha development)  Hughes Lake – 43 ha open water (333 ha development)  Wood Lake – 33 ha open water (192 ha development)

Future Land Use

Grande Prairie Stormwater Drainage Master Plan Proposed Future Development Plan

Additional Evaluations  Post development discharge rate for some water    

courses. Design guidelines for fore bays. Design guidelines for 25 year ponds. Design guidelines for linear drainage corridors/linear storage facilities. Flood line mapping.

North East

South East

South West

West

North West

Design Standard Review  Draft Design Manual 2018 for Circulation – Section 12  Standards been reviewed for:  General requirements  Minor System  Major System  Stormwater Management Facilities  Comparison to other municipalities:  City of Edmonton  Strathcona County  AEP Standards and Guidelines  Recommendations:  Design Storms  Pond Control Structures  Water Quality Control

Design Storm Review  Current IDF Curve is based on rainfall data at Grande

Prairie Airport from 1968 to 1993.  The IDF curve was discontinuous at the 2 hour duration.  Rainfall hyetograph used a 10 minute discretization.

IDF Curve Review â&#x20AC;&#x201C; Additional Gauges

Location of Selected Rainfall Gauges in Proximity of City of Grande Prairie

IDF Curve Review â&#x20AC;&#x201C; New Curves

Rainfall Intensity (mm/hr)

100

New IDF 1000-yr New IDF 100-yr New IDF 50-y r New IDF 25-y r

New IDF 10-y r New IDF 5-yr New IDF 2-yr Current IDF 100-yr Current IDF 50-yr Current IDF 25-yr Current IDF 10-yr Current IDF 5-yr

Current IDF 2-yr

28 10

100

Rainfall Duration (minutes)

1000

IDF Curve Review â&#x20AC;&#x201C; New Design Rainfalls 90

New 4-hour Chicago 5-yr Current 4-hour Chicago 5-yr

160

New 4-hour Chicago 100-yr Current 4-hour Chicago 100-yr

Rainfall Intensity (mm/hr)

140

120

100

29 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240

Rainfall Intensity (mm/hr)

180

Rainfall Duration (minutes)

New SWMF Control Structures  Current Design Requirements:

Orifices or Hydrobrakes

From Pond

 Recommended:

Outlet Control Structures  Combination of weir, gate,

    

orifice, and/or other hydraulic components Outlet maintenance Water level control Drawdown requirement Bypass flow Overflow

HWL

NWL Orifice Emergency Outlet Maintenance

Introduction of Water Quality Design Guidelines  Water Quality Control Parameter  Sediment, floatables  Components Considered  Oil / Grit Separator – suitable for

commercial development and for existing end of pipe treatment of small basins.  Forebay Design – minimum event retention, bypass design to prevent sediment re-suspension during sever storms, maintenance facility.  Low Impact Development (LID) – Constructed Wetlands, Bioswale, etc.. 31 Image Source: Google

City of Grande Prairie Storm Drainage Master Plan Questions / Comments

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) â&#x20AC;&#x201C; May 9, 2018

Appendix B: Display Boards

Sameng Inc.

City of Grande Prairie

City of Grande Prairie Storm Drainage Master Plan

Stakeholder Open House May 9, 2018

LEGEND CITY BOUNDARY

ALBINATI INDUSTRIAL

PROPERTY LINE WATERCOURSE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE LAND USE LEGEND

A BE

132 AVENUE

RESIDENTIAL

EE CR

PUBLIC SERVICE

100 STREET

COMMERCIAL INDUSTRIAL

CRYSTAL LAKE

URBAN RESERVE MUSKOSEEPI PARK DIRECT CONTROL

AR BE

116 AVENUE

AIRPORT

K EE

CARRIAGE LANE ESTATES RESERVOIR

HIGHWAY 43

116 STREET

SILVER POINTE

92 STREET

108 STREET

84 STREET

100 AVENUE

84 AVENUE

WOOD LAKE

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

SANDRY RIDGE ESTATES

CLAIRMOUNT LAKE

BEAR CREEK

BEAR LAKE

Client:

68 AVENUE

HERMIT LAKE

132 AVENUE EE

100 STREET

HUGHES LAKE

AR BE

RESOURCES ROAD

CR EE

FLYINGSHOT LAKE

CRYSTAL LAKE

116 AVENUE K

EE CR RESERVOIR

HIGHWAY 43

92 STREET

84 AVENUE

WOOD LAKE

68 AVENUE

RESOURCES ROAD

RIN

G CR

FLYINGSHOT LAKE

108 STREET

116 STREET

84 STREET

100 AVENUE

BEAR CREEK

BEAR BE

SP RIN G CR EE K

CR EE

CREEK

SPRUCEWOOD PARK

WEDGEWOOD BE

EE K

WILLOWOOD ESTATES

Project:

Storm Drainage Master Plan 2018 Title:

Existing Land Use

TAYLOR ESTATES Scale:

Figure:

1:40,000

4-9

TRADITIONAL DESIGN CONCEPT

ROADWAY CB

HWL 100 YEAR / 24 HOUR EVENT

STORM SEWER

NWL

5YR DESIGN

FLOOD LEVEL

5 L/s/H

OUTFALL CREEK

NATURAL DESIGN CONCEPTS

OVERLA ND FLOW

ROADWAY CB STORM SEWER

5YR DESIGN

FOREBAY

PATHWAY

CHANNEL

FLOOD LEVEL

SCENARIO 1: ADJACENT TO SUITABLE OUTLET

NORMAL LEVEL

ROADWAY CB 25 YEAR / 4 HOUR EVENT

STORM SEWER 5YR DESIGN

OVERLA ND FLOW

NWL FOREBAY

PATHWAY

CHANNEL

SCENARIO 2: FAR AWAY FROM SUITABLE OUTLET

FLOOD LEVEL NORMAL LEVEL

HIGHWAY 2

LEGEND

BEAR CREEK

B1 BEAR LAKE

CLAIRMOUNT LAKE

CITY BOUNDARY PROPERTY LINE STORMWATER MANAGEMENT FACILITY (WET)

STORMWATER MANAGEMENT FACILITY (DRY)

LAKE

B2 C3

HIGHWAY 43X

MAJOR OVERLAND FLOW DIRECTION

HIGHWAY 43

BASIN BOUNDARY BASIN DRAINING INTO EXISTING STORM SYSTEM

A1 D2

EXISTING HIGHWAY

FUTURE HIGHWAY E2

AREA STRUCTURE PLAN

V10 AR

HIGHWAY 43X

H6 I4

C AR BE

V12

V13

G14

G16 G10 G0

G15

SILVER POINTE

G17

K1 K2 K3 K4

CARRIAGE LANE ESTATES

V3 RESERVOIR

84 AVENUE

100 AVENUE

92 STREET

HIGHWAY 43

116 STREET

G13 HIGHWAY 43

116 AVENUE

HIGHWAY 40 108 STREET

P11

V2 HIGHWAY 43

G12

P10

CRYSTAL LAKE

84 STREET

G11

EK RE

M6 N2

P2 SECONDARY HIGHWAY 670

V11

100 STREET

EE CR

PROPOSED FOREBAY P4

M1 132 AVENUE

PROPOSED STORMWATER MANAGEMENT FACILITY P1

HUGHES LAKE

H1 G1

PROPOSED WATER RETENTION CORRIDOR M3

OUTLINE PLAN - 1224ha IN DEVELOPMENT ALBINATI INDUSTRIAL

HERMIT LAKE

HIGHWAY 43

W1 WOOD LAKE

Prepared By: TO

BE AR

CR EE K

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

W3 SANDRY RIDGE ESTATES

Client:

68 AVENUE

BE AR

RESOURCES ROAD

CR EE

FLYINGSHOT LAKE

SPRUCEWOOD PARK

WEDGEWOOD

SP RIN G

CR EE K

BE AR

Project:

TAYLOR ESTATES

Storm Drainage Master Plan 2018

REEK

BEAR C

Title:

CR EE K

Future Development Plan

HIGHWAY 40

WATER TREATMENT PLANT

WILLOWOOD ESTATES

Scale:

Figure:

LEGEND CITY BOUNDARY

HIGHWAY 43

PROPERTY LINE STORMWATER MANAGEMENT FACILITY (WET)

ALBINATI INDUSTRIAL

STORMWATER MANAGEMENT FACILITY (DRY) LAKE

MAJOR OVERLAND FLOW DIRECTION BASIN BOUNDARY

BASIN BOUNDARY (OVERFLOW) BASIN DRAINING INTO EXISTING STORM SYSTEM

EXISTING HIGHWAY

P5 M2

AREA STRUCTURE PLAN

M1 L1

FUTURE HIGHWAY

OUTLINE PLAN

132 AVENUE

SECONDARY HIGHWAY 670

P10

PROPOSED WATER RETENTION CORRIDOR

PROPOSED STORMWATER MANAGEMENT FACILITY

P11

PROPOSED FOREBAY

N2 P8

N1 100 STREET

CRYSTAL LAKE

P7 P9

116 AVENUE Q2 Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Project:

Storm Drainage Master Plan 2018

N1 - KINGSGATE LANDING OP Title:

Future Development Natural Drainage North East Scale:

Figure:

N.T.S.

LEGEND CITY BOUNDARY PROPERTY LINE

BEAR LAKE

BEAR CREEK

STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY)

LAKE MAJOR OVERLAND FLOW DIRECTION

BASIN BOUNDARY BASIN BOUNDARY (OVERFLOW) BASIN DRAINING INTO EXISTING STORM SYSTEM

EXISTING HIGHWAY FUTURE HIGHWAY

AREA STRUCTURE PLAN

OUTLINE PLAN PROPOSED WATER RETENTION CORRIDOR PROPOSED STORMWATER MANAGEMENT FACILITY PROPOSED FOREBAY

A1 D2

A3 D3

E1 E3 F1

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Project: D2, D3 - BORROW PIT FOR HIGHWAY 43X

Storm Drainage Master Plan 2018 Title:

Future Development Natural Drainage North West Scale:

Figure:

N.T.S.

LEGEND CITY BOUNDARY PROPERTY LINE

STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE

BASIN BOUNDARY BASIN BOUNDARY (OVERFLOW)

SANDRY RIDGE ESTATES

WOOD LAKE

CARRIAGE LANE ESTATES

BASIN DRAINING INTO EXISTING STORM SYSTEM EXISTING HIGHWAY FUTURE HIGHWAY AREA STRUCTURE PLAN OUTLINE PLAN

PROPOSED WATER RETENTION CORRIDOR

W2 Q3

PROPOSED STORMWATER MANAGEMENT FACILITY

WILLOWOOD ESTATES

N3 Q2

PROPOSED FOREBAY

M6 84 STREET Q1 N1

CRYSTAL LAKE

132 AVENUE

SECONDARY HIGHWAY 670

MAJOR OVERLAND FLOW DIRECTION

Prepared By:

R1, R2 - MEADOWVIEW ASP R3 - FIELDBROOK OP

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Q1, Q2, Q3, Q4, Q5 - WEST CARRIAGE LANE OP

Project:

Storm Drainage Master Plan 2018 Title:

Future Development Natural Drainage South East Scale:

Figure:

N.T.S.

LEGEND

CITY BOUNDARY

I4 H3

E AK

MAJOR OVERLAND FLOW DIRECTION BASIN BOUNDARY BASIN BOUNDARY (OVERFLOW)

H HIG

BASIN DRAINING INTO EXISTING STORM SYSTEM EXISTING HIGHWAY

G13

G11

Y4 A HW HIG

MI ER

LAKE

3 Y4

STORMWATER MANAGEMENT FACILITY (DRY)

T EE R T 6S

ES GH

KE LA

STORMWATER MANAGEMENT FACILITY (WET)

ET RE T 8S

H1 F2

PROPERTY LINE

G12

FUTURE HIGHWAY

4 AY

HW G I H

OUTLINE PLAN PROPOSED WATER RETENTION CORRIDOR

G15

G14

PROPOSED STORMWATER MANAGEMENT FACILITY

G17

AREA STRUCTURE PLAN

G16

PROPOSED FOREBAY

R VE

G8 G10

IN PO

SIL

G9 G0 G4

T HO S NG

YI FL

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

Project: K1, K2, K3, K4 - KENSINGTON OP

Storm Drainage Master Plan 2018 Title:

G13 - NORTHWEST ASP G14, G15, G16 - AIRPORT INDUSTRIAL OP

Future Development Natural Drainage South West Scale:

Figure:

N.T.S.

LEGEND

CITY BOUNDARY

PROPERTY LINE STORMWATER MANAGEMENT FACILITY (WET) STORMWATER MANAGEMENT FACILITY (DRY) LAKE MAJOR OVERLAND FLOW DIRECTION

BASIN BOUNDARY

V10

BASIN BOUNDARY (OVERFLOW) BASIN DRAINING INTO EXISTING STORM SYSTEM

A BE

FUTURE HIGHWAY

K EE CR

HUGHES LAKE

EXISTING HIGHWAY

V11

AREA STRUCTURE PLAN OUTLINE PLAN

PROPOSED WATER RETENTION CORRIDOR

PROPOSED STORMWATER MANAGEMENT FACILITY

PROPOSED FOREBAY

V5 H6

HIGHWAY 43X

G11 G7

V12

V1 V13

G12

RESERVOIR

Prepared By:

#1500, 10025-106 St., Edmonton, Alberta T6J 1G3 Ph: (780)482-2557, Fax: (780)482-2538 Email:services@sameng.com

Client:

V1, V2 - WEST TERRA OP V3 - EXISTING V4, V5, V6, V7, V8, V9, V11 - HIDDEN VALLEY ASP V10 - ARBOR HILLS ASP V12, V13 - NORTHWEST ASP

Project:

Storm Drainage Master Plan 2018 Title:

Future Development Natural Drainage West Scale:

Figure:

N.T.S.

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) â&#x20AC;&#x201C; May 9, 2018

Appendix C: Sign-in Form

Sameng Inc.

City of Grande Prairie

Stormwater Master Plan 2018 Stakeholder Open House Report (Revision 1) â&#x20AC;&#x201C; May 9, 2018

Appendix D: Feedback Forms

Sameng Inc.

City of Grande Prairie

Storm Drainage Master Plan 2018 Final Report (Revision 1)

City of Grande Prairie

Appendix G: Computer Model of Storm Drainage System Provided to City as a separate file.

Sameng Inc.