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Table 3.10 — Recommended Fire Flows for Residential Land Uses Distance Between Fire Flow Needed at Buildings (ft) 20 psi (gpm) More than 30 500 21-30 750 11-20 1,000 Less than 10 1,500 rt — reet; GNM — Gallons per Minute Fire protection needs can vary widely based on the physical characteristics of each building and municipal fire insurance ratings are partially based on the water distribution system's ability to provide needed fire flows up to 3,500 gpm. Knowing this, Table 3.11 summarizes the fire flow requirements projected for the northeast study areas based on the anticipated land uses. These requirements are only intended to be used as a general planning guideline at this time. Table 3.11 — Projected Fire Flow Requirements — Northeast Study Area Land Use Type Approximate Needed Fire Protection m Single Family Residential 500 — 1,500 Mixed Residential 2,000 — 3,000 Neighborhood Commercial 1,500 — 2,500 GPM — Gallons per Minute The available fire flows modeled for the northeast study area are shown in Figure Al2 in Appendix A. The lowest available fire flow modeled for the study area is 2,400 gpm, which is located within single family residential land use. Mixed residential and commercial land uses in the northeast study area are projected to have an available fire flow of 3,500 gpm or higher. Modeling indicated that the majority of the study area will have an available fire flow greater than 3,000 gpm. 3.6 System Evaluation and Capacity Analysis for Northwest Areas Computer modeling indicated that the northwest study areas cannot be annexed to the existing water distribution system without the use of a separate pressure zone as the ground elevations are significantly higher than the rest of the system. Upon consulting with ERMU staff, a hybrid approach was taken to serve these areas through the use of new production wells and booster stations. Although booster stations are not needed if multiple new wells are drilled in the northwest areas, it is strongly recommended to use booster stations to reduce capital expenses since fewer wells will be needed initially to supply drinking water. Because the northwest areas will be mostly isolated from the existing system, the supply, treatment, and storage infrastructure evaluation was completed for the future northwest areas alone without taking into account the system's main pressure zone like for the northeast areas. Since the rate of development for the northwest areas is unknown, the water demands summarized in Table 3.7 were distributed linearly between now and the end of the planning period. The water supply capacity evaluation for the northwest study areas is depicted in Figure 3.5. This study proposes supplying the study areas with a hybrid approach of two (2) booster stations and a single well for a total initial combined firm pumping capacity of 800 gpm (1.15 MGD). As development increases, a new 850 gpm well could be drilled within five (5) to ten (10) years to increase the northwest area's firm pumping capacity to 1,650 gpm (2.38 MGD). Additional wells can be drilled beyond 2040 to serve the ultimate development boundary. Feasibility Report Northeast & Northwest Urban Service Area Expansion Study City of Elk River, MN WSB Project No. 020010-000 Page 10