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Minnesota DNR could place a moratorium on additional wells. These conditions do not appeaz [o be <br />likely in the short term but they could manifest themselves in the next 10 to 15 yeazs. <br />4.2 New Wells in the Surficial (Unconsolidated) Aquifer <br />4.2.1 Description <br />The sand and gravel of the Surficial aquifer in the Elk River area is likely very permeable and capable <br />of yielding lazge quantities of water where the saturated thickness is greater than about 50 feet. <br />Locating these areas (and delineating their extent) would likely require a combination of surface <br />geophysical surveys and test drilling. Wells completed in the Surficial aquifer could supplement the <br />existing Mt. Simon-Hinckley wells. <br />4.2.2 Technical Feasibility and Reliability <br />Utilizing Surficial unconsolidated aquifers through wells is generally a proven method for obtaining <br />water supplies. Surficial aquifers are generally more subject to reduced yields during extended <br />drought conditions. Surficial aquifers are also more likely to become contaminated by land use <br />activities and typically have higher levels of nitrate and pesticides than bedrock aquifers (although <br />these levels are typically below drinking water standards). Surficial wells have a higher likelihood <br />than bedrock aquifers to become contaminated by spills and leaks. Pumping in the Surficial aquifer <br />could reduce recharge to the underlying Mt. Simon-Hinckley Aquifer. <br />4.2.3 Cost <br />The cost for a Surficial well system would likely be slightly less than the cost for a similar Mt. <br />Simon-Hinckley well system, due to reduced drilling costs for shallower wells. However, the cost <br />differential is likely small. In some locations, a Mt. Simon-Hinckley well and a Surficial aquifer well <br />could be located close together without causing yield losses due to well interference effects. This <br />could result in some cost savings in piping and land acquisition. <br />4.2.4 Challenges and Other Considerations <br />Pumping from the Surficial aquifer may reduce recharge conditions (over the long term) to the <br />underlying Mt. Simon-Hinckley aquifer. Wells located very near the Elk River or the Mississippi <br />River may be deemed to be "under the direct influence of surface waters" by the Minnesota <br />Department of Health and may require much more stringent treatment. <br />P:\Mpla\23 MN\71\2371105 Water Supply Alternative Study\PinalDelive~ables\Alrernntives_Repoc[_final.do° 29 <br />