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4.4 Artificial Recharge by Infiltration Basins <br />4.4.1 Description <br />Raise regional groundwater levels, increase aquifer storage, and promote additional recharge to the <br />surficial aquifer and the Mt. Simon-Hinckely Aquifer by routing runoff and precipitation into <br />permeable basins (e.g., abandoned aggregate mines). Natural process will act on the infiltrating water <br />to remove suspended sediment and many water-borne contaminants. Increased water levels can <br />increase the available drawdown in existing wells, thereby increasing the lnaximum yield. Reduced <br />yield during extended droughts can be minimized. <br />4.4.2 Technical Feasibility and Reliabili#y <br />Promotion of infiltration in basins is a widely practiced in some watersheds in the metro area and is <br />an emerging best management practice. Infiltration basins improve the water quality of surface-water <br />bodies by reducing runoff during the first parts of high-intensity precipitation events. Reductions in <br />recharge caused by urbanization can be reversed and recharge can be increased even beyond natural <br />levels. Implementation is not complicated. <br />4.4.3 Cost <br />The cost of implementation is relatively small and sites for future infiltration can be incorporated into <br />land ttse plans. Basins are typically left dry but vegetated. Some land may be lost from future <br />development. <br />4.4.4 Challenges and Other Considerations <br />Increased infiltration may not necessarily translate into meaningful increases groundwater <br />availability to wells. In general, the water quality of infiltrated water is likely as good or better than <br />the water quality of infiltration through natural soils. However, the temperature of some infiltration <br />basin water may be higher. There is also the potential to raise water levels in the surficial aquifer to <br />such an extent that they might cause wet basement conditions near the infiltration basins (although <br />these conditions can be substantially mitigated through proper design). This approach would <br />indirectly affect available water supplies but would not necessarily represent a new water supply. <br />4.5 Collection and Treatment of Mississippi River Water <br />4.,5.1 Description <br />Construct an intake structure on the Mississippi River and treat the pumped water in a surface-water <br />treatment plant. <br />P:\Mpls\23 MN\7l\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 31 <br />