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The concept plan for the distribution system and WTPs is segmented into four phases for two different <br /> WTP location sites as demonstrated on Figure ES-1 The phased watermain and water treatment plant <br /> locations are shown on Figures ES-2 and ES-3. <br /> Figure ES-1.Phased Approach to Trunk Watermain Construction <br /> PHASE Al(WTP in Ramsey):A backbone 36"' <br /> waterma in is constructed connecting Ra imsey, <br /> Dayton,and Rogers. Serves water demands <br /> through 2040. <br /> PHASE A2(WTP in Dayton):A backbone 36" <br /> waterma in is constructed con recti ng Ra nosey, <br /> PHASE D: Dayton,and Rogers. Serves water demands <br /> Ultimate th,mLigh 2040. <br /> P14W withLoop Ultimate System PH AS E B: Extend 16"wateormain to Corcoran, <br /> All Communities meets 2 MGD demands, <br /> PHASE 6: <br /> Expand to PHASE C, Extend 36"waterma in to Corcoran, <br /> Corcoran meets Corcoran ultimate demands. <br /> PHA SEA: PHASE DI(WTP in Ramsey): Complete 36" <br /> 2040—Dayton, watermain loop;meets ultimate demands. <br /> Ramsey,Rogers PHASE D2(WTP in Dayton): Complete 36" <br /> watermain loop-,meets Ultimate demands. <br /> Approach 1 — Regional Surface Water Treatment Plant <br /> Several Minnesota communities have the Mississippi River as their source of drinking water, including <br /> St. Cloud, St. Paul Regional Water Services, and Minneapolis. It was determined that the Mississippi <br /> River in the vicinity of the Northwest Metro has sufficient capacity and water quality to serve the <br /> ultimate water demands of the communities. Two locations were considered for a potential regional <br /> surface water treatment plant, including a location in Ramsey and a location in Dayton. <br /> To protect public health from pathogens, surface water used for drinking water is required to follow the <br /> US EPA's Surface Water Treatment Rule. To meet maximum day demands, the 2040 capacity of the <br /> water treatment plant is 25 MGD and the ultimate capacity is 75 MGD. <br /> Approach 2 — Regional Groundwater Treatment Plant <br /> A regional groundwater treatment plant would utilize wells in a central wellfield for its source water. To <br /> reduce chlorides in wastewater from home softeners and compare the groundwater WTP against a lime <br /> softening surface WTP, it is assumed that the potential regional groundwater WTP is a lime softening <br /> WTP. The groundwater treatment plant is proposed to be located in Dayton because it is centrally <br /> located, less developed than Rogers or Ramsey, and the Tunnel City Wonewoc aquifer is available <br /> throughout the entire City. <br /> The concept regional groundwater WTP is proposed to provide a capacity of 25 MGD and would serve <br /> the maximum day demands for the Northwest Metro communities through 2040. After 2040, the <br /> groundwater WTP will be expanded to 75 MGD to meet ultimate water demands. <br /> Approach 3 — Conjunctive Use <br /> A hybrid option for the Northwest Metro to utilize some of its groundwater infrastructure is to build a <br /> new water treatment facility with a surface water source for conjunctive use with the existing <br /> groundwater systems. Conjunctive use is using treated surface water to meet average day demands <br /> and peaking with existing groundwater wells. <br /> Approach 3 consists of constructing a 12 MGD surface WTP to meet 2040 demands and a 28 MGD <br /> expansion (total of 40 MGD) to meet ultimate demands. The 2040 average day demand for the <br /> Northwest Metro is 7.8 MGD and the ultimate average day demand is 29 MGD. The WTP capacities <br /> are designed to be larger than the average day demands so that the water treatment plant does not <br /> need to be operated 24 hours per day. <br /> Page—ES-2 I METROPOLITAN COUNCIL <br />