8.3 SR 02-06-2023 - Laserfiche WebLink

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3.5 Recommended Water System Infrastructure for the Northeast Areas The proposed water distribution system to serve the northeast study areas is shown in Figure A9 in Appendix A. A summary of the recommended infrastructure is described below: Trunk Watermain: Prior to extending water service to the northeast study areas, it is recommended to connect the existing 16-inch watermain along Cleveland Street NW with the 12-inch watermain stubbed at the intersection of Twin Lakes Road NW with 193�d Avenue NW using a 12-inch watermain. A 12-inch watermain can then be extended north along Twin Lakes Road NW until reaching the intersection with 209th Avenue NW. From this location, the 12-inch trunk can be directed west along 209th Avenue NW and south along Quincy Street NW. From there, the 12-inch trunk can be extended south along Smith Street NW and Tyler Street NW to connect to the existing trunk watermain along 193�d Avenue NW. Additionally, a 12-inch trunk watermain should be extended along 201 St Avenue NW to create a smaller trunk loop. The trunk watermain for this study area can be extended in phases. Eight-inch watermain can be extended from the proposed 12-inch trunk loop to provide water service to the northeast study area via smaller watermain loops. The smaller 8-inch watermain loops shown in Figure A9 are not definitive and their final location will change based on future development layouts. Wells: Additional wells beyond the future 850 gpm production well that is proposed for 2028 are not needed to serve the northeast study areas. This new well does not need to be drilled in the northeast area itself as long as it provides water to the main pressure zone since both areas will be interconnected. Water Towers: A new 1.0 MG water tower is needed to serve the northeast areas. Water Treatment Plants: The pressure zone's water treatment capacity must be increased to serve the northeast study area. This can be done by providing direct filtration treatment at the future 850 gpm well planned for 2028 if its water does not meet drinking water standards. Pressure Zones: The entire northeast area can be served off of the system's existing main pressure zone without the need of pressure regulating infrastructure. The average day and peak hourly water pressures for the northeast study area are shown in Figures A10 and A11. Water pressures were modeled using Bentley OpenFlows WaterGEMS CONNECT (WateGEMS) software based on the proposed watermain layout shown in Figure A9. Water pressures were modeled using a conservative scenario where all the City's wells were turned off and the water level in the City's water towers were 10-ft below the overflow elevations. The modeled water pressures were compared against the Ten-States Standards which recommend that working distribution pressures be 50 to 80 psi, and not lower than 35 psi. Modeling indicated that water pressures can be maintained between 50 psi and 81 psi for average day demand conditions and between 47 psi and 81 psi for peak hourly demand conditions. Booster Stations: Larger distribution system booster stations will not be required to serve the study area. However, private internal booster stations may be needed at dwellings with a ground elevation of 990-ft or higher to maintain water pressure above 35 psi in second stories of single family homes. Less than 5-percent of the study area has ground elevations at or above 990-ft. PRVs: Pressure reducing valves (PRVs) will be needed in the southwest corner of the study area at individual dwellings with a ground elevation below 915-feet in order to maintain the water pressure below 80 psi per the Minnesota Plumbing Code. However, this area is mainly nondevelopable, so it is likely that not many services will require PRVs. Fire flow recommendations provided by the AVWVA for residential land uses were used to assess the fire flow requirements for the majority of the northeast study areas. According to the AVWVA, the minimum fire flow available at any given point in a water distribution system should not be less than 500 gpmwith a residual pressure of20 psi. This represents the amount ofwater required to be provided by two standard hose streams on a fire in a typical residential area for dwellings with spacing greater than 30 feet. Minimum fire flow recommendations increase as the distance between dwellings is reduced. The recommended AVWVA fire flows for residential land uses are shown in Table 3.10. Feasibility Report Northeast & Northwest Urban Service Area Expansion Study City of Elk River, MN WSB Project No. 020010-000 Page 9