Agenda - Council Work Session - 10/20/2020 - Special

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2.3 2,4 Existing System Available Flow for Fire Protection Designing a water system to provide adequate fire protection is an important consideration. Adequately sized watermain is an important consideration to supply desired fire flows. Guidelines for determining fire flow requirements are provided by the ISO. 150 is the insurance service organization responsible for evaluating and classifying municipalities for fire insurance rating purposes. Available fire flow for fire protection (fire flow) in this report is defined as the flow capacity at a point in the water distribution system which causes the pressure to fall to 20 psi (residual pressure). A map of the fire flow analysis for the distribution system under a maximum day demand is shown in Figure 8 in Appendix B. Note that the fire flow analysis for the distribution system was done for junctions (watermain intersections and at dead -ends) instead of hydrants, so the fire protection in some areas may be better than shown as a hydrant may be nearby on a larger sized watermain. In general, low fire flows occur where normal pressures are already low, and in areas with small diameter watermains, or in areas with older watermains. Dead -ends typically have noticeably weaker fire flows than looped watermain as well. To determine if the water system is deficient in available fire flow, a basis for fire protection must be established. For planning purposes, the minimum fire protection requirement can be based on land use according to Table 4. Table 4 - Minimum Fire Flows Land Use Park Flow (g pm) ..._ 500 Single -Family 1,000 R-1 Low -Density Single Family 1,000 Two -Family 1,000 M ulti-Family 1,500 High -Density Multi -Family 1,500 Service Office 1,500 Community Commercial 2,500 General Commercial 2,500 Industrial 3,500 Mixed Use -Neighborhood 2,000 Mixed Use -Community I 2000, Mixed Use -Regional 2030, In general, the City is well protected with over 98% of the distribution system having fire flows of 1,500 gpm or higher. When comparing availabie fire flows with the City's existing land use map there are a few areas where the available fire flow may be deficient. Specifically, a small industrial and use area north of Highway 10 and south of the southern dead-end of Jaspar Street NW, as well as the dead-end of 142nd Lane NW in the southeastern part of town. Existing System 24-Hour Simulation -- Treatment Plant Similar to the existing system 24-Hour simulation, a 24-hour extended period simulation was run for ADD and MDD demands to model how the existing system performs in terms of pressure, velocity, and tank levels with a treatment plant as the sole source &water. With a single source FEASIBILITY STUDY -DRAFT RAMSY 154354 Page 6