8.3 SR 02-06-2023 - Laserfiche WebLink

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(e.g., irrigation demands) that is not reflected in the wastewater flow. In the case of Elk River, the system- wide average water demand is approximately 61 percent higher than the City-wide average sanitary sewer flow. Due to this stablished relationship between flows, water demands for the study areas were projected using a demand per dwelling assumption that was calculated using lift station run time data provided by City staff. To be conservative, a 75 percent factor, instead of Elk River's 61 percent difference, was applied to the lift station run time data to calculate residential water demands. A detailed lift station run time data analysis is provided in Section 4.3 of this report. Industry-standard water demand rates were used for non- residential land uses. Average water demands for the study areas were projected using the unit water demand flows summarized in Table 3.5. Table 3.5 — Water Demand per Land Use Assumptions Land Use Type Density Residential Unit Average Unit (units/acre) Flow (gpd/unit) Flow (gpd/acre) Single Family Residential — Northeast Areas 2 145 290 Single Family Residential — Northwest Areas 3 145 435 Mixed Residential 5 145 725 Neighborhood Commercial - - 900 Highway Business - - 900 Public/Semi Public - - 0 Open Space/Parks - - 0 Unft — resfdentfal dwellfng; gpd/acre — Gallons per Day per Acre The projected water demands calculated for the study areas are summarized in the tables below. The maximum day peaking factor used corresponds to the main zone's average peaking factor from Table 3.4. Table 3.6 — Projected Water Demand for Northeast Areas Land Use Type Net Developable Average Unit Water Water Acres Demand (gpd/acre) Demand (gpd) Single Family Residential 1,012 290 293,480 Mixed Residential 307 725 222,503 Neighborhood Commercial 9 900 8,100 Average Daily Flow (gpd) 524,083 Maximum Daily Flow (gpd) 1,357,375 Table 3.7 — Projected Water Demand for Northwest Areas (2040 Development Timeframe) Land Use Type Net Developable Average Unit Water Water Acres Demand (gpd/acre) Demand (gpd) Single Family Residential 1,393 Varies�'> 282,599 Mixed Residential 266 725 192,850 Highway Business 41 900 36,900 Public/Semi Public 29 0 0 Open Space/Parks 202 0 0 Average Daily Flow (gpd) 512,349 Maximum Daily Flow (gpd) 1,326,984 (1) A large portion ot the area is already developed with densities signiticantly lower than 3 units/acre. I heretore, densities vary throughout which affect average unit water demands. Investigating the serviceability of the ultimate northwest areas beyond the year 2040 was not included in the scope of this study. However, a high level preliminary analysis was completed to assess the water demands expected beyond 2040 as this could affect trunk watermain sizing recommendations. The planned Feasibility Report Northeast & Northwest Urban Service Area Expansion Study City of Elk River, MN WSB Project No. 020010-000 Page 5