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5.4 Treatment Processes <br /> Iron and manganese are removed from water by adding oxidants, typically chlorine and sodium <br /> permanganate, which convert the iron and manganese from soluble compounds to filterable solids. <br /> The iron and manganese are subsequently removed in the filtration process. <br /> The lime softening, recarbonation, and filtration processes are the same as surface water treatment <br /> described in Section 4.4. A chlorine contact tank is not necessary for groundwater treatment due to the <br /> lack of pathogens. <br /> 5.5 Wells <br /> The average Tunnel City-Wonewoc well in the Northwest Metro communities produces about 800 gpm, <br /> except Rogers where the assumed well capacity is 500 gpm. This production rate will be used in <br /> establishing the supply for a regional groundwater treatment plant. It is assumed that the wells will be <br /> spaced at least 0.25 miles apart. It is assumed that the permitting, testing, drilling, and building costs <br /> for each new well is $1,500,000. <br /> 5.6 Estimate of Probable Capital Cost <br /> The following tables provide capital costs for a lime softening groundwater treatment plant that would <br /> meet 2040 demands (25 MGD) and ultimate demands (75 MGD). <br /> Table 5-2 provides a concept level cost estimate for a 25 MGD lime softening groundwater treatment <br /> plant. A layout for a 25 MGD lime softening groundwater WTP is included in Appendix D. It is <br /> assumed that 20 acres of land would be required to construct a 25 MGD surface WTP (including room <br /> for future expansion) plus easements for the raw water line (total of 23 acres). To meet 2040 demands, <br /> 22 new wells in Dayton would be required. Table 5-2 presents costs in 2020 dollars. <br /> Table 5-2.Concept Level Cost for 25 MGD Lime Softening Groundwater Treatment Plant. <br /> Item Quantity Units IL Unit Cost Total Cost <br /> 25 MGD Lime Softening Lump <br /> Groundwater Treatment 1 $68,000,000 $687000,000 <br /> Plant Sum <br /> New Wells 22 Each $17500,000 $331000,000 <br /> Raw Watermai n 30,000 Feet $300 $97 000,000 <br /> Easements/ Land 23 Acres $100 000 $2 300 000 <br /> Acquisitions ' <br /> Environmental 6 Miles $507000 $3007000 <br /> Subtotal $112,6009000 <br /> Contingency (30%) $337800,000 <br /> E n g/Ad m i n/Legal (20%) $29,300,000 <br /> Total $176,0009000 <br /> Page—26 1 METROPOLITAN COUNCIL <br />