Restoration Design in the Pacific Northwest by maddie.mccort

Restoration Design in the Pacific Northwest

ESRM 479 Spring 2020 Maddie McCort

Cover Images (left to right): Washington Department of Fish and Wildlife, 2008 Matia Contractors, Inc., 2016 Marcellus Preserve, Hannah Letinich

Prepared for Jim Fridley ESRM 479 Restoration Design

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Table of Contents Project 1: Wiley Slough ....................................................................... 3 Project 2: Union Bay Natural Area....................................................13

Wiley Slough Saltmarsh Restoration

Washington Department of Fish and Wildlife, 2008

Introduction The Wiley Slough Restoration Project is located in the Skagit Wildlife Area on the Skagit Bay in Northwest Washington (see Figure 1: Wiley Slough in NW Washington). The site was historically a saltmarsh, and we are addressing dikes installed in the late 1950’s and early 60’s for agriculture and recreation (Wiley Design Report). Our goal is to convert this land back to open tidal influence while balancing stakeholders such as the Washington Department of Fish and Wildlife, the Skagit River System Cooperative, and the Skagit Watershed Council.

Figure 1: Wiley Slough in NW Washington

Site Analysis Current State: Wiley Slough is owned by the State of Washington, and managed by the Department of Fish and Wildlife. In 1956, a levee system was created to prevent the Wiley Slough area from natural river and tidal floods (Wiley Design Report). Tide Gates prevent flooding of farmland and saltwater-freshwater mixing. Not only did this change the Wiley Slough ecosystem, but shifts in hydrology and sediment transport created altered environments up and downstream of the levees and tidal gates. Prior to the levees, estuarine flooding provided 160 acres of intertidal marsh habitat to many species, notably the Chinook salmon. Currently, tide gates and levees inhibit salmon migration in Wiley Slough. The current use of the site consists of pheasant and waterfowl hunting.

Figure 2: Existing topography at Wiley Slough restoration site. Wiley Slough Design Report. Draft. 4/1/05.

Environmental Functions: Vegetation on the site consists of forestation along dikes and berms, as well as annual cereal grain plantings. Historically, Wiley Slough was between forested riverine tidal and estuarine emergent habitats. Currently, the area is managed as public hunting and wildlife land and the ecosystem supports pheasants and waterfowl. Impacts on Historical Ecosystem: The historical ecosystem was altered completely when the area was diked. The water was drained and the land used for upland purposes. Fish and wildlife like salmon, bull trout, cutthroat trout, sturgeon, shorebirds, waterfowl, and harbor seals have lost 20 acres of tidal channel habitat. The tidal channels have since accumulated sediment from erosion on surrounding land, creating smaller channels.

Proposed Site Design We recommend removing dike B, C, and D, and using excavated material to reinforce dike A. The old tide gate should be removed, and a new one added on the eastern side of dike A (see Figure 3 below).

Figure 3: Proposed site design for restoration of Wiley Slough

Design Reasoning The goal of our design is to restore Wiley Slough as close to historical conditions as possible, in line with the desire of local tribes while protecting the interests of adjacent agricultural activity, and the public. Natural processes, functions and biological conditions will again provide estuarine habitat for the native wildlife and plant communities. We will achieve this by removing dikes so that tidal and riverine flooding may occur naturally. We chose to remove the spur dike (dike C) despite the hydrology of the adjacent river because it interferes with connectivity between the east and west sides, and we believe hinders salmon use. We will relocate the tide gate in order to protect upstream farming from flooding. The addition of a new loop trail in the northeast corner will provide a public recreation opportunity. In addition to these structural changes, we will remove invasive vegetation that has a likelihood of surviving in salt marsh conditions, and plant native species.

Functional Requirements This design was commissioned by the Skagit Watershed Council and the Washington State Department of Fish and Wildlife. Our functional requirements include the following: -Introduce tidal influence to the restoration area -Increase value of restoration area for wildlife usage -Eliminate invasive species -Increase diversity of native salt marsh plant and animal species -Retain public recreation access on the site

Alternative Restoration Options One design alternative we explored is to leave Dike C. This dike has the smallest interference with tidal and riverine flooding, and could be left to reduce project cost. To achieve desired levels of repair, we decided against this option. A second alternative design would be to move the eastern half of dike A north of the channel so that no tide gate would be required. This option would require more labor and money as the old dike would be removed, and a new one constructed. We decided against this option for the project budget. One restoration option we considered was planting more native saltmarsh species other than just Scirpus americanus and Carex lyngbyei. This would likely speed up habitat restoration but increase the project cost.

Stakeholders Washington Department of Fish and Wildlife Skagit River System Cooperative Hunters Bird Watchers

Interest(s) Balance between people and conservation Restoration of salmon spawn Preserving suitable hunting land Accessible wildlife habitat

Seattle City Light

Unaffected public utilities

Federal Government

Protect wildlife, educate public

Planting Plan Scirpus Americanus will be planted in areas with an elevation between 6 and 9 feet, and Carex lyngbyei will be planted in areas above 9 feet in elevation (see figure 4). See Table 1 for planting estimations. Carex is a native salt marsh plant that thrives in elevations between the mean low high water to the mean high high water (Ewing, 1986). We will plant in this area and seed dispersion will naturally occur to lower elevations as well. Scirpus Americanus dominantes the range below Carex, so we will plant it in that range and hope for natural dispersal to both higher and lower elevations (Ewing, 1986). Other native salt marsh species will enter naturally from surrounding areas as ecosystem restoration occurs over time. Table 1: Estimations for Planting Plan Species Scirpus Americanus Carex Lyngbyei

Elevation Total Area (sq ft) Number of Plants 6-9 ft 1,800,000 800,000

Cost (Sound Native Plants) $80,000

>9ft

$17,333

390,000

173,333

Figure 4: Proposed planting plan for restoration of Wiley Slough

Constraints The existing constraints identified are preventing farmland flooding, preventing the alteration or disruption of existing habitat, working around salmon spawning season, retaining recreational access, and working within a budget. Farmers using land adjacent to the Wiley Slough Restoration area restrain the level of repair possible. Northern dikes must remain so that saltwater intrusion does not disrupt crop production. Constraints from conservation groups and native tribes include protecting existing habitat and wildlife. Construction must occur during a time that salmon are not spawning as it would disrupt this process. Recreational access is an important function of this area, and restoration should not remove this. An environmental impact statement may be required for government groups and the public. Finally, we have been constrained to choose the best restoration option in the most cost-effective way. We have attempted to satisfy every stakeholder but some compromises will be required.

Predicted Level of Repair Possible Return of tidal processes will allow this site to perform former environmental functions. The site is likely to experience mid to high levels of repair. Return of salmon will likely occur within one year of dike removal, and result in coupled ecological functions. The removal of invasive species will help ensure that native species will survive. Planted vegetation will spread to non planted areas naturally, and no maintenance of invasive vegetation should be required. Wiley Slough will be restored to a similar level of environmental function as occurred before dike construction. We chose not to remove fill from increased sedimentation upriver because of the cost and equipment needs. Although returning channels to natural width and depth may allow for higher levels of repair, dredging material could negatively impact channel ecosystems. Erosion will occur naturally over time, and a functioning salt marsh ecosystem will result from our chosen level of repair.

Likelihood of Autogenic Repair If dikes are not removed, Wiley Slough is highly unlikely to repair itself. It is possible that autogenic repair could occur, but it would require dike failure which might occur after an extremely long amount of time, or in the case of a natural disaster like an earthquake. Invasive vegetation would prevent restoration of native species, and dikes would continue to prevent natural sedimentation. Dike removal or failure is required for ecological restoration to occur.

Dike Removal and Reinforcement Process Planning for the removal and reinforcement of present dikes establishes expectations and baselines that keep the project in check. The dimensions of current and proposed dikes are found in Table 2.

Table 2: Old and Reinforced Dike Dimensions Old Dike

Reinforced Dike

Height

10ft

Height

12ft

Width

8ft

Width

20ft

Slope Ratio (R)

2.5

Slope Ratio (R)

To carry out the removal and reinforcement process, we decided to use the Cat 307E2, or similar, Mini Hydraulic Excavator. This smaller sized excavator is able to maneuver on top of the narrow eight foot wide dikes that are found throughout the restoration site, making it an ideal option for this particular project.

Cat 307E2 Mini Hydraulic Excavator (Photo from Cat Website)

Table 3: Specifications of Cat 307E2 307E2 Specifications Dig Depth

13.4 ft

Track Width

7.2 ft

Bucket Capacity

0.13-0.48 cubic yards

Average Bucket Capacity

.305 cubic yards

Dike Area and Volume It is important to have a good idea of the amount of material that is to be removed, transported, and unloaded. Knowing this information dictates the number of dump trucks, excavators, and associated work hours that are needed to complete the project. The total calculated volume of dirt for each dike we are interacting with can be found in Table 4 below. Table 4: Dike Area and Volumes Section and Status of Dike

Cross Sectional Volume of One Area (sq ft) Lineal Foot (cubic yards)

Length (ft)

Total Volume (cubic yards)

Removed Dike (B, C, D)

330

12.22

12366

151140

Existing Dike to 330 Be Reinforced (A)

12.22

5414

66171.11

Reinforced Dike 672 (A)

24.89

5414

134748.44

We estimate the removal of 166,254 yds3 of fluffed dirt from Dike B, C, and D. This was calculated by assuming a 110% volume increase as a result of the digging process. Dike removal needs to be completed or at least halfway done before the start of reinforcement. In order to limit the cost associated with the 80,679 yds3 of fluffed dirt needed to reinforce Dike A, we plan to reuse that which was removed from B, C, and D. Truck loads from removal to reinforcement sites can be documented to make sure the right amount of material is being transferred. There will be approximately 85,575 yds3 of excess dirt that will have to be redirected off site before it is unknowingly deposited at a finished reinforcement site. After testing the soil for contaminants the excess can be sold to other restoration or construction projects nearby. Table 5: Number of Truckloads Required 10 yd3 10yd3 Truckloads Truckloads per Lineal Foot

14 yd3 14 yd3 Truckloads Truckloads per Lineal Foot

Total Load Time 3 10 yd3 trucks (Based on 30 min Pickup to drop off)

16,626

1.34

11,876

.96

1,662.6 hours

Reinforcement 14,823

2.74

10,588

1.96

1,482.4 hours

Removal

Estimating the amount of time needed gives v and construction workers the ability to budget and organize the project. By using two Cat 307E2 Mini Hydraulic Excavators and three 10 yd3 trucks, we believe this project could be done in a matter of 3,145 hours or 314.50 days based on 10-hour construction days. Buckets to Fill 10 Cubic Yard Truck: 32.79 Reinforced Levee buckets: 545,095.1 buckets Removal Levee Buckets: 264,521.3 buckets

Task Sequencing and Schedule Chinook salmon spawn during the summer (May-July) (Hinton et al. 2005) so excavation will not occur within this timeframe. 1. Non-native and invasive species that have the ability to survive after dike removal will be removed from the site to prevent persistence. 2. Remove dike D. 3. Use the material from the deconstructed dike (D) to then reinforce dike A to the south of the farms. 4. Construct a new tidegate at the eastern side of the reinforced dike (A). 5. Remove dike B, dike C and the existing floodgate, allowing saltwater to flood into the target area. 6. This material from dikes B and C will be used for further reinforcement, and the excess will be discarded. 7. Plant native saltmarsh species to begin ecosystem restoration. Scirpus americanus and Carex lyngbyei 8. Check in on habitat status (biodiversity/water salinity/invasives) one month post construction. 9. Based on results of step 8, take further steps if necessary. 10. Make future wildlife/levee checks as necessary. 11. Establish hiking trail for public recreation access Note: see “Subprojects” / Figure 3 for hiking trail

List of Potential Pitfalls and How They Should be Avoided This restoration project comes with pitfalls, as all projects do. We predict that a main issue may be flooding impeding construction, as we will conduct all construction from August-April. These months tend to be very rainy and since construction is already taking place in a marsh, flooding is inevitably a risk. To reduce this risk the weather and flooding hazard will be checked daily, and if the risk is high, construction will be halted during that time. Construction staff will also be given instruction on how to safely exit the site in the case of an unpredicted flood.

Another pitfall could be the disturbance of native species and the soil. Although using such machinery will inevitably create some amount of disturbance, this can be reduced by replanting species in the construction areas after construction has taken place and by keeping heavy machinery in designated areas and pathways. This would reduce the overall area of damaged soil and prevent any newly planted species from being disturbed by construction. One current pitfall could be budget cuts due to COVID-19. Although construction is still considered an essential business, hours would likely be reduced until the shelter in place is lifted, which would be until the end of the construction season. Therefore, this project will not be able to begin until August 2021 with time for planning, unless the shelter in place is not lifted by then. That does, however, give our team time to contact native people, gather funds, and further survey the site.

Subprojects As a possible subproject, we propose granting public access via one or more hiking trails or paths through the saltmarsh. The purpose of this would be to create a connection between the local community and the restored saltmarsh. It is more common for people to care for the environment if they have an emotional attachment to or a positive experience with it. Therefore, allowing people to explore the saltmarsh on designated paths without endangering themselves or the wildlife would be beneficial for the saltmarsh’s protection. For this subproject we propose that a loop trail is created around the northern part of Wiley Slough, as indicated by the orange trail in Figure 2. This would be a mile loop far away from the most protected areas of the saltmarsh. If the budget allows, educational signs with information on native plants, animals and ecosystem functions present in the saltmarsh could be included on these trails. To further engage the community with their local saltmarsh, volunteer work parties could be organized by the WDFW or the Skagit Watershed Council to help maintain the integrity of the newly restored saltmarsh. Volunteers could help with our continuing activities such as weeding out returning invasive species and maintaining hiking trails. These work parties could integrate educational elements as well in order to further foster a relationship between individuals and the saltmarsh.

Continuing Activities A proper monitoring and maintenance schedule is necessary to ensure restoration efforts are sustained and effective. The actions carried out are certainly subject to deterioration and even reversal. Beginning with the dikes, structural integrity and overall performance need to be documented each year. Our decision to reinforce Dike A came from the fact that they are susceptible to erosion and lose their functionality over time. Measuring dimensions (height, width, slope ratio) should provide enough information to determine their condition. Seasonal water heights in relation to the dikes could also be recorded to see if the reinforced height is adequate. Other than dike integrity, there are many things which should be monitored going forward such as native species success and invasive species return. Monitoring native plants, along with tagging of some native animal species, will allow us to estimate general ecosystem health and predict relative function of the ecosystem. If invasive species return after removal, it is essential that these be removed in order for the native species success. Another essential continuing activity is monitoring the relationship between the local community and the newly renovated area. We suggest a survey be sent out every six months to the owners of surrounding farmland to ensure they have had no problems or concerns, as well as a general public survey to see if the public is engaging with our restored area. Questions can include: Have you used the new trails at the Wiley Slough saltmarsh? How were the trails maintained? Do you have suggestions for improvement?

Chapter References “The Alphabet Soup of Vertical Datums: Why MHHW Is Mmm Mmm Good.” Inside the Eye, 29 Jan. 2016, noaanhc.wordpress.com/2016/01/29/the-alphabet-soup-ofvertical-datums-why-mhhw-is-mmm-mmm-good/. Caterpillar Performance Handbook. Caterpillar Inc., 2008. Ewing, Kern. “Plant Growth and Productivity along Complex Gradients in a Pacific Northwest Brackish Intertidal Marsh.” Estuaries, vol. 9, no. 1, 1986, pp. 49–62. JSTOR, www.jstor.org/stable/1352193. Accessed 16 Apr. 2020. Hinton, S., J. Blank, A. McKain, G. Hood, and B. Williams. 2005. Wiley Slough Estuarine Restoration Design Report. Final Draft. Washington Department of Fish and Wildlife, Olympia, WA. Hinton, S, J Blank, A McKain, G Hood, et al. 2005. Wiley Slough Estuarine Design Report. “Wildlife Areas.” Washington Department of Fish & Wildlife, wdfw.wa.gov/places-to-go/ wildlife-areas/skagit-headquarters-wildlife-area-unit. Sound Native Plants, “Wholesale Price List.” Ecological Restoration Specialists, soundnativeplants.com/nursery/wholesale-price-list/?doing_wp_cron=1587692103.4 191739559173583984375. Wiley Slough Design Report. Draft. 4/1/05.

Union Bay Natural Area Wetland Restoration

Matia Contractors, Inc., 2016

Introduction The Union Bay Natural Area (UBNA) is on the north shore of Lake Washington in Seattle (see Figure 1). The marshland was created in 1916 by the lowering of Lake Washington and the site was used for over 40 years as the Montlake Landfill (Caldbick, 2013). The landfill was closed in 1966 and now, the Washington Department of Transportation is seeking to use it as a wetland mitigation project. The reconstruction of SR 520 Evergreen Point Floating Bridge resulted in the disturbance of many freshwater and fringe lacustrine wetlands. We are exploring the option to create a wetland in UBNA where a parking lot currently resides. The E-5 parking lot (see Figure 3) is an aggregate lot that has been maintained since 1970. This restoration atop a landfill poses unique challenges to not only restoring biodiversity, ecosystem services, and wildlife habitat, but also retaining public access to recreational use, and educational purposes.

Figure 1: Union Bay Natural Area in Seattle, WA

Site Analysis Site History This site has been maintained as a gravel parking lot since 1970. It has no vegetation and is mostly flat on top of silty-fine to medium sand mixed with gravel. Historically, the area was a part of a larger shoreline wetland created when the Ballard Locks lowered Lake Washington by 9 feet (King County, 2017). Before this, marshy emergent wetlands occurred as a result of the accumulated logs, plant debris, and soil at Ravenna Creek (The Union Bay Planning Committee, 1995). The Locks now maintain water levels of 22 feet elevation in the summer and 20 feet in the winter. Union Bay Natural Area contains multiple vernal pools that dry up in the summer. Environmental Functions The wetland ecosystems in UBNA perform functions and services such as providing habitat, recreation, and educational opportunities. Historically this area has been habitat for large populations of native plant species and wildlife including waterbirds and threatened species like the Western Pond Turtle and Red Sliders (The Union Bay Planning Committee, 1995). The proposed wetland in the parking lot will provide habitat for these

species and many more birds, amphibians and invertebrates. The historic wetland ecosystem provided a natural filtration and sedimentation process for water entering the lake, and this is a function we intend to restore with our design (Mitsch and Gosselink 2015). Impact on Historical Ecosystem Because the site is currently a parking lot, restoring it to a wetland will have major consequences for the surrounding ecosystems. It will replace an inhospitable environment with habitat for native species. This will likely increase biodiversity for the greater Union Bay Natural Area. The surrounding wetlands may receive less water at times due to water being diverted into the new wetland, but we do not expect this to have harmful consequences to the overall ecosystem. To mitigate flooding of existing wetlands, we will direct flooding to the southwest corner of the site.

Stakeholders US Fish & Wildlife Services

Interested in the protection and restoration of wetland habitat for fish and wildlife.

Washington Department of Ecology and Wetlands

Work to restore, maintain, and protect wetlands in the interest of the various services provided by this ecosystem (water quality, reduction of flooding, aquifer recharge) (WSDOE, 2020)

The Center for Urban Horticulture & UW Botanical Gardens

Interested in providing opportunity for outdoor research and public services (such as experiencing nature and wildlife watching) (UWBG, 2019)

Seattle Audubon Society

Interested in restoration of the wetlands to expand bird habitat and increase the potential for recreational bird watching in the greater Seattle region

King County

Interested in maintaining water quality of the region and reducing environmental impact of the project (King County, 2017)

Seattle District Reservoir Control Center; WSDOT

Interested in road closures and safety of construction/demolition (WSDOT, 2020)

Seattle District Reservoir Control Center; USACE

Interested in the level of water in Lake Washington as it pertains to fish passage, ship canals, and locks (US Army COE, 2019)

The University of Washington

Interested in keeping this area open for research, for both students and staff

Constraints Union Bay Natural Area is located on the former Montlake Landfill. This landfill was capped in 1971 but still poses unique challenges to restoring wetland ponds (The Union Bay Planning Committee, 1995). In order to create a wetland, soil must be removed from the site. Landfill material is contaminated and requires expensive disposal and safety precautions to avoid harm from methane production (UW Environmental Health and Safety Department and Montlake Landfill Oversight Committee 2015). In order to keep the project within a reasonable budget we will not dig into the landfill material, and instead make sure a 2.5 foot cap of soil sits on top of it.

Likelihood of Autogenic Repair Without restoration, this site in the Union Bay Natural Area has little to no chance of repairing itself. This is because following the closure of the landfill which resided in this area, it became a maintained gravel lot. Although some autogenic repair of vegetation may occur along the edges of the pavement, autogenic repair of the entire wetland system within this block of pavement is unlikely. Due to the changes in land use over time, invasives or other non-wetland species that have colonized around the pavement could impede the growth of historic species of the area, again decreasing the likelihood of autogenic repair. There is a very small potential that a natural disaster, such as a large earthquake, could potentially break up the pavement’s surface and allow natural restoration to begin. However, with the historic landfill underneath the pavement and presence of non-wetland or invasive species, even with the destruction of the paved area, autogenic repair may be extremely slow, and although ecological restoration may occur, it still may not transform this area into a well functioning wetland. This is why it is vital that this area undergo additional restoration efforts in order to return this area into a productive, healthy, wetland ecosystem.

Predicted Level of Repair Possible Low

Minimum habitat requirements met Minimum drainage occurs No filtration or sedimentation.

Mid

Habitat for few species Landfill capped Drainage successful Limited natural filtration.

High Habitat for many species, plant and animal Natural filtration and sedimentation

Functional Requirements Wetland capable of seasonal flooding Opportunities for educational uses Increase the quality of habitat for wildlife use Decrease likelihood of invasive species spread Increase diversity of plant and animals species Public interaction with the site Provide area for research and recreational uses Increase filtration and sedimentation of collected water Increase water storage capacity of UBNA

The restoration of this wetland will allow this site to regain many environmental functions and services. Low levels of repair would meet minimum habitat and drainage requirements and have little to no sedimentation or filtration within the system. However, with this proposed restoration plan, the site is predicted to have mid to high levels of repair. This level of repair includes the capping of the preexisting landfill, creation of habitat, natural filtration and sedimentation processes, and successful drainage. The creation of habitat for many plant and animal species, paired with natural drainage and filtration processes, will result in an ecosystem which provides many services to the surrounding area. New habitat will also yield new inhabitants, increasing the diversity and complexity of the ecosystem over time. This would not have been possible without the capping of the landfill underneath this proposed wetland, and this area will transform from a low functioning, relatively inhospitable environment, to a high functioning, well adjusted wetland ecosystem.

Hydrology The drainage basin for this project is about 213,000 square feet. Using data from the 19812010 Climate Normals from the National Climatic Data Center, monthly temperatures and precipitation were determined from the Sand Point station.

Figure 2: Drainage Area for Proposed Wetland

For our design to be successful, we will want to remove as much fill as possible in the E-5 lot. Because of the underlying landfill, our plan includes digging down to 6 inches above the landfill material, placing a bentonite membrane and then adding two feet of topsoil. Using the Soil Boring map, we estimated the topography of the underlying landfill material, and added 2.5 feet to represent the topography after the cap. This topographic estimation is represented in Figure 3 below. This map suggests that when the lot is excavated there will be a pool in the middle/ southern section. The total gravel that would need to be removed is 88,800 cubic feet. Based on Lake Union levels, any elevation above 22 feet will remain dry year round (US Army Corps of Engineers). Soil will be added to the edges of the lot that are below this elevation to direct flooding in desired locations. A channel will exist on the southwest corner where outflow will occur to Lake Washington. The wetland will outflow to the lake, but inflow from the lake to the wetland will not occur. Our wetland will rely on the hydrology of rainfall and flooding from the drainage zone in Figure 2. The difference between the monthly precipitation and evaporation rates from average pan evaporation data in the Seattle Maple leaf area was determined. Using these values, we calculated the cubic feet per month of flow into our wetland.

Figure 3: Estimated Topography of Underlying Landfill

Table 1: Drainage Area Monthly Runoff

In the event that the wetland is full or a storm occurs, we will have a natural channel that carries outflow from the wetland into the lake. This channel will have a bottom width of 2 feet, flowing 1.25 feet deep. This results in a flow rate of 6.4 ft3/sec (Hydraulics Manual, 2017). This size will not overflow under normal, or 2 year storm conditions. Table 2: Stream Velocity Using Manning’s Equation

Table 3: Storm Runoff Flow Values

Proposed Topography Given the hydrology calculated, we decided to design a wetland with 59,000 ft3 of volume capacity (See Figure 4). In the months of January through March, our wetland will flood because it will fill up to the 21 ft topography line which has the capacity to hold 36,000 ft3 of water. This overflow will be directed to our channel in the southwest corner of the site. We chose to build the northeast corner of our site to a higher elevation to prevent overflow from occurring here and flooding the trail. In a 50 or 100 year storm event where the outflow from our wetland exceeds the outflow channel capacity of 6 ft3/s, the wetland will fill up to the 22 ft line, which has the capacity to hold 59,000 ft3 of water. We estimate the total overflow volume throughout an entire year to be 20,000 ft3, considering that water will leak through sides and into surrounding soil. In the months of August and September, our wetland will dry out.

Figure 4: Proposed Wetland Topography

Table 4: Monthly Pond Volume

Table 4.1: Pond Volume Calculations

Plant Design Terminology (Cowardin, 1979) Palustrine Emergent (PEM): Erect, rooted, herbaceous hydrophytes; vegetation present for majority of growing season Palustrine Scrub-Shrub (PSS): Woody vegetation less than 20 feet tall; dominated by shrubs and small trees Palustrine Forested (PFO): Woody vegetation more than 20 feet tall Planting Design and Selection A main priority of this restoration project is the planting of a diverse selection of native wetland species. Transforming what is now a gravel parking lot into a functional habitat will require a significant amount of effort in not only the actual planting process, but also the propagation that supplies the species themselves. This project looks to interact with the University of Washington’s Society for Ecological Restoration (SER) Nursery to provide the native plantings. Located in the Center for Urban Horticulture within Union Bay Natural Area proper, the SER Nursery will simplify the planting efforts by acting as an onsite source. Selections were made via their Spring 2020 available catalog. As this is a larger scaled restoration project, wholesale prices were used to estimate the cost per plant. Container stock was chosen for each species, making the transportation from the nursery to the site straightforward. Planting locations are based upon the creation of a central wetland pool. Winter precipitation is expected to fill its capacity in the months outlined in the previous section. The characteristic drought weather of Washington summers will likely dry the pool for at least one to two months. In order to plant species in conditions that suit their own specific biology, four Zones were identified within the pool and its outflow regions. Volume calculated for each elevation contour interval led to the determination of flooding and saturation periods. The Zones increase in elevation, with Zone 1 starting at the pool’s low point of 18’. Selecting plants for each zone was done by referencing both the individual’s water regime (Stevens and Vanbianchi, 1993) and wetland community (Cowardin, 1979) inhabited:

Figure 5: Proposed Planting Plan

Table 5: Designated Planting Zones. SF=Seasonally Flooded, SS=Seasonally Saturated, PEM=Palustrine Emergent, PSS=Palustrine Scrub-Shrub, PFO=Palustrine Forested

Table 6: Species to be planted, including their stocktype, spacing, count, price, growing conditions, and wetland community inhabited.

Table 7: Number and costs of plants selected for each Zone. Total cost of plant order is approximately $2,450.

Cross Section Profiles

Figure 6: Labelled Cross Sections

Sequencing and Timing Table 8: Project Timeline

Recommendations Regarding Site Work and Installation Excavated material disposal A majority of our excavated material will be used for creating a barrier around our wetland, any contaminated soil encountered will be incinerated, and remaining non-contaminated excess soil can be used for other city projects or landfill cover. Excavator buckets and Truckloads. Truck = 10-15 cubic yards of dirt this equates to 59,300*1/27= 2196.29 cubic yards/10 = 219.63, 2196.29/14 = 156.89 so estimated 156.89-219.63 truckloads depending on exact truck size. Excavator = 2196.29/0.69 cubic yards =~3,183.04 excavator buckets Estimate time required for earthwork We recommend the use of a hydraulic excavator because it can excavate 242.4242 m3 or 317.08 CY this equates to about 7, 10 hour days of excavation. Our Total project completion time is approximately 5 months.

Cost estimate We are providing an approximate cost based Ameron Construction 2016-2017 rate book at 70 hours of work. The actual cost and time can vary based on company, equipment, personnel, and unforeseen circumstances. Generally a hydraulic excavator can excavate at an average rate of 85,61 cubic feet per day. We plan on using a 315 Caterpillar Hydraulic Excavator with a compactor at $169 per hour with a GD 0.53 m³ (0.69 yd³) bucket size. This is a standard sized excavator and is recommended as the most popular excavator for commercial construction work. As for trucks, we are recommending and basing the cost on a single axle, two ton dump truck, which costs $79 per hour. Bentonite clay waterproofing costs $3.53 per square foot on average with labor added to nail one layer in place. Made of corrugated cardboard and clay, it forms a barrier between the foundation and any wet soil from outside. Table 9: Cost Calculations

Continuing Activities Assessments will need to be performed after completion in order to test water quality, plant growth, and water movement in the wetland. We also recommend an assessment on land use in the wetland and surrounding areas to see how local species are taking to the new habitat. The wetland flooding regime will be observed to ensure plantings will succeed. Monitoring and maintenance will continue to ensure the long term success of the wetland. Additional planting may be needed in the future to meet changing conditions. Educational signage about the wetland will be installed along the trail after the wetland is completed to encourage University use of the area.

Chapter References Caldbick, J. 2013. Union Bay Natural Area (Seattle). History Link. Available from: http://www.historylink.org/File/10182 “Climate Normals.” National Climatic Data Center, www.ncdc.noaa.gov/data-access/ land-based-station-data/land-based-datasets/climate-normals. Cowardin, L. M., V. Carter, F. C. Golet, E. T. LaRoe. 1979. Classification of wetlands and deepwater habitats of the United States. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. Jamestown, ND: Northern Prairie Wildlife Research Center Online. http://www.npwrc.usgs.gov/resource/wetlands/classwet/index.htm (Version 04DEC1998). King County. 2017. The Lake Washington Story. Accessed May 2, 2020. http://www. kingcounty.gov/environment/water-and-land/lakes/lakes-of-king-county/lakewashington/lake-washington-story.aspx Mitsch, W.J. and J.G. Gosselink. 2015. Wetlands. 5th ed. Hoboken, NJ: John Wiley & Sons, Inc. pp. 527-562, 591-646. “Publications - Hydraulics Manual.” WSDOT, 16 Apr. 2019, www.wsdot.wa.gov/ Publications/Manuals/M23-03.htm. Stevens M, Vanbianchi R. 1993. Restoring Wetlands in Washington: A Guidebook for Wetland Restoration, Planning & Implementation. Washington State: Department of Ecology The Union Bay Planning Committee. 1995. Management for the Union Bay Shoreline and Natural Areas. University of Washington, Seattle, WA. University of Washington Environmental Health and Safety Department, Montlake Landfill Oversight Committee. 2015. Montlake Landfill Project Guide. University of Washington, Seattle, WA. US Army COE. (2019, February 11). Corps of Engineers begins Lake Washington annual summer refill. News Release. US Army Corps of Engineers. “Reservoir Control Center.” USACE Seattle District Water Management, www.nwd-wc.usace.army.mil/nws/hh/www/index.html. UWBG. (2019, June 14). Union Bay Natural Area. Retrieved from https://botanicgardens. uw.edu/center-for-urban-horticulture/visit/union-bay-natural-area/

WSDOE. (2020). Wetlands. Retrieved from https://ecology.wa.gov/Water-Shorelines/ Wetlands WSDOT. (2020, May 5). SR 520 Bridge Replacement and HOV Program. Retrieved from https://www.wsdot.wa.gov/Projects/SR520Bridge/default.htm “Excavator Sizes: Choosing the Right One for Your Project.” BigRentz, 4 Mar. 2020, www.bigrentz.com/blog/excavator-sizes. Rate Analysis of Excavation in Earthwork -Calculate Cost of Excavation. “Rate Analysis of Excavation in Earthwork -Calculate Excavation Cost.” The Constructor, 18 Sept. 2017, theconstructor.org/practical-guide/rate-analysis-of-excavation-in-earthwork/9617/.