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The water treatment capacity evaluation for the main pressure zone is depicted in Figure 3.3. The zone's <br />existing firm water treatment capacity is 5,140,800 gpd (3,570 gpm) and it is anticipated that water treatment <br />be provided at the new 850 gpm well proposed for 2028 if needed to meet drinking water standards. As <br />shown in the figure below, increasing the zone's treatment capacity by providing treatment at the new well <br />will be sufficient to meet the projected maximum day demands for the northeast service areas. <br />� <br />p 6.0 <br />C� <br />� <br />� <br />� <br />� 4.0 <br />a� <br />0 <br />L <br />� <br />� <br />� �.O <br />O.O <br />2�22 <br />Date (yyyy) <br />�Firm Treatment Capacity Projected Maximum Day Demand <br />Figure 3.3 — Main Pressure Zone Water Treatment Capacity Evaluation <br />At a minimum, a municipal water distribution system should have enough water storage capacity to exceed <br />the system's average day demand. However, water systems should also have enough storage capacity to <br />meet the maximum day demand as well as additional volume for fire protection and equalization storage. <br />Calculating storage requirements this way often results in a lower storage requirement volume if a system <br />has excess supply capacity that can augment the system's storage capacity. The overall equation to <br />determine recommended storage capacity based on maximum day demand, fire projection, and pressure <br />equalization is as follows: <br />Equation 3.1 — Water Storage Calculation <br />Required Water Storage Volume = Adjusted Fire Storage (AFS) + Equalization Storage <br />where <br />AFS =(Maximum Day Demand + Fire Requirements — Firm Capacity) x Design Fire Duration (Hours) <br />Firefighting volume requirements vary based on land uses and specific commercial, industrial, and <br />institutional uses. Firefighting requirements are based on guiding documents, including Ten States <br />Standards, AVWVA, and the Insurance Services Office (ISO); but fire flow requirements are usually at the <br />discretion of each community. For system-wide water storage calculations, such as the ones completed for <br />this study, a conservative available fire flow of 3,500 gpm for three (3) hours is often used as recommended <br />by the AVWVA and ISO. <br />Equalization storage is the volume required to satisfy water demands that exceed the well pumping capacity <br />throughout the day. During any given day, hourly demands vary as a diurnal demand pattern with the <br />maximum hour demand designated as the peak hour demand. Equalization storage is determined by <br />calculating the volume necessary to meet the peak hour demand beyond what the firm supply capacity can <br />provide. The AW1NA recommends the required equalization volume to equal 70 to 100 percent of the <br />average day demand, or 20 to 25 percent of the maximum day demand. <br />Feasibility Report <br />Northeast & Northwest Urban Service Area Expansion Study <br />City of Elk River, MN <br />WSB Project No. 020010-000 <br />Page 7 <br />2024 2026 2028 2030 2032 2034 2036 2038 2040 <br />