Water Model Development for Freeze Protected Water System in Iqaluit, Nunavut Marilyn Fanjoy*, Ken Johnson*, Marc Lafleur*, Eric Bell*, Sumon Ghosh** *EXP Canada: marilyn.fanjoy@exp.com, ken.johnson@exp.com, cryofront@gmail.com **City of Iqaluit: s.ghosh@iqaluit.ca
Iqaluit, Capital City of Nunavut
Reservoir Flow
o Located on Baffin Island in Frobisher Bay o Population ~8,000 Iqaluit
Water System General Overview: o o o o o o o
Surface water supply Water Treatment Plant Storage Reservoir – 4.1 million Litres 7 Water Districts Total 2 Pressurized Districts with Booster Stations 5 Gravity Districts ̴ 32.5 km watermain (25 mm to 300 mm diameter) o 3 neighborhoods serviced by truck fills o Measured system demand = 3.54 ML/day
1.Total system measured average day demand=3.54 ML/day=1,292,100 m^3/year on June 11, 2021 2.Calculated flow closely follows measured for a typical day 3.Overnight lower demand, morning peak, highest peaks for truck fills 4.Peaks between 8:30 AM and 5:30 PM attributed to truck fill operations at BS1 5.Demand during off peak hours (12AM-6AM) higher than expected/not significantly lower than daytime; indicates a significant amount of water is bled from the system 6.Calculated reservoir discharge flow ̴ 0.1 ML/day lower than measured SCADA during low flow between 12 am and 6 am; indicates the fixed flow bleeds may not all be accounted for or bleed rate may be inaccurate. 7.Bleed flow approx. 10% of total water usage
Cold Climate Specific Components
Reservoir Level
Utilidor Consisting of: o Buried and insulated watermains o Looped piping; no dead ends o Heat addition and recirculation pumps; closed system o Bleeds maintain low usage circulation to prevent freezing o Insulated Access vaults – common water/sanitary and surface fire hydrants o Truck Fill stations o Seasonal variation in demand – bleeds active 8 months per year
Water Model Uses o Determination of system wide operating pressures and flowrates o Calculation of available fire flows o Trouble shooting water system issues o Identifying opportunities for system upgrades o Future design planning for system expansion o Water age analysis o Flushing program development o Contaminant tracing o Design for system upgrades and future expansion assessed with “what-if” scenarios in the model
Water Model Development o Bentley WaterGEMS Software o Water system physical layout and attributes o Record drawings: 1. Pipe length, diameter, material, and installation date 2. Storage reservoir capacity and dimensions 3. Booster station piping arrangement, pipe diameter, and material o Elevation data – record drawings and extracted from contour mapping o Hazen Williams head loss coefficients for various pipe materials and installation dates o Operational parameters (storage tank levels, pump on/off setpoints) from City staff and SCADA o Water user demands – calculated and adjusted for measured total consumption o Thermal model developed with Excel spreadsheets and low flow rates from hydraulic model
Field Data o Typical day measured total consumption o Calibrate one district at a time • Plateau district chosen first o SCADA trends o Hydrant Flow Tests
1. Initial filling rate of reservoir similar to measured 2. Calculated drainage rate faster than measured between 12AM and 8AM – indicates the low flow demand from bleed locations may be too high or adjustment of demand pattern may be required. Further field data required to confirm.
Findings o Hydraulic model calculation comparisons to SCADA trends • Close agreement between model results and SCADA trends • Water temperature leaving Booster BS2 was excessively high ▪ 15°C to 25°C; the station heating system is intended to maintain a maximum output temperature setpoint of +/- 10° • Minimal temperature depression between the supply and return flow of Booster BS2 indicating short circuiting o Hydrant Flow Tests for Plateau District • Poor flow test results indicate the fire pump and pressure control valve are not operating properly o Phase 1 identified system deficiencies for maintenance and repair
Conclusions o o o o o o o
Bleeds may not all be accounted for and rates may be low. User demands may be too high overnight; demand pattern may require modification. A short circuit is suspected between the supply and return distribution mains in BS2. A working model of the water system has been established. Further hydrant flow testing is required to achieve calibration for each district. Hydrant flow testing may proceed following resolution of operational issues. Identification of further unknown operating conditions are expected in the hydrant testing and model calibration process.
Phase 1 of the project has identified issues in need of resolution prior to completion of field flow tests. Phase 2 of the project will complete hydrant flow tests required for model calibration. The water model will then be ready to be used as a design tool for assessing the current water system, proposed modifications or upgrades and future expansion.