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Approach 4 — Status Quo — Individual Lime Softening Water Treatment Plants <br /> In the absence of a project driver or an incentive to do something different, the Northwest Metro cities <br /> will most likely continue to utilize groundwater in separate water systems. <br /> To provide an equivalent comparison to Approaches 1-3, it is assumed that the Northwest Metro cities <br /> will continue to drill wells as needed and construct lime softening WTPs. A potential driver for selecting <br /> a lime softening treatment process for community drinking water systems is a future wastewater <br /> discharge limit for chlorides in the Twin Cities metro area receiving waters. The majority of the chloride <br /> in wastewater comes from the regeneration process of home water softeners. <br /> The number of new wells and the capacities of the lime softening water treatment plants in Approach 4 <br /> is based on the 2040 and ultimate water demands of the individual Northwest Metro cities. To meet <br /> ultimate demands using only groundwater, it is estimated that an additional 54 wells will be needed. <br /> Approach Comparison <br /> The four approaches are compared through an analysis using 20-year and 60-year planning horizons. <br /> The 2040 Regional System Plan is based on meeting the 2040 demands for Dayton, Ramsey and <br /> Rogers and assumes that the ultimate water trunk main is extended to Corcoran by 2040. For the 60- <br /> year planning period, the system capacity is expanded from 2040 to accommodate the ultimate or <br /> buildout conditions of all four communities. <br /> Table ES-1 summarize the lifecycle costs for water system facilities to meet 2040 demands. The three <br /> regional drinking water system approaches and continuing with the `status quo' of separate community <br /> systems are compared. <br /> Page—ES-5 I METROPOLITAN COUNCIL <br />