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generally occur in areas of lower elevation (see the Gem Lake elevation map in Appendix F). White Bear Lake's Century Avenue storage facility has an overflow elevation of 1,125 feet and their Centerville Road storage facility has an overflow elevation of 1,129 feet. Gem Lake system pressures projected with those overflow elevations and during a peak hour MDD scenario (assumed to be 130% of the MDD in gallons per minute) can be seen in the map in Appendix E. Water distribution system pressures are generally recommended to be in the range of 35 psi to 80 psi. As can be seen in the map in Appendix E, White Bear Lake's water system can provide a Gem Lake distribution system with adequate pressures, with the lowest pressures seen where elevations are higher west of the lake. It should be noted that the modelling assumed White Bear Lake's towers are full and it would be expected that pressures would periodically be a few psi lower as White Bear Lake's tank elevations vary from water usage throughout the day. Modeling shows that pressures should still be adequate in the Gem Lake system with slightly less elevation in the White Bear Lake storage towers. 3.1.2 Gem Lake - ' l site Bear Lai. Pipe V �. jcitIr Pipe velocities are generally recommended to be kept below five feet per second to limit headloss, or pressure loss, due to friction across the system and to limit potential pipe and valve damage. As can be seen in the map in Appendix E, the proposed watermains were sized to limit velocities to below 1.5 feet per second. 3.1.3 Gem Lake �'t."hite Bear L, ,,e A- An important Consideration for a water system is being able to provide adequate fire protection. Having appropriately sized watermain as well as enough storage in the system are important factors in available fire protection flow. Guidelines for determining fire flow requirements are provided by the Insurance Services Office (ISO), which is the insurance service organization for evaluating and classifying municipalities for fire insurance rating purposes. For the purposes of this study, it is assumed that meeting the MDH recommendation of having an average day of water use in storage is sufficient and minimum fire protection requirements can be based on land use according to Table 6. Available fire flow in this study 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, which is the minimum needed pressure before a boil water advisory is required. In general, low fire "- --- where normal pressures are already low, in areas with small diameter s, and in areas with older watermains where significant headloss occurs due to Table 6 — Minimum Fire Flows FEASIBILITY STUDY UPDATE City of Gem Lake, MN Page 7