5.2. SR 08-08-2011 - Laserfiche WebLink

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Available Geology and Existing Surrounding Wells Currently, there are only private wells adjacent to the study area that serve either residential and/or irrigation water supply needs. According to a review of the County Well Index, no private or public wells are contained within the AUAR study area. There are other existing residences in and adjacent to the study area that are assumed to have private wells as the properties are not served by the City's Water System, but the locations of these wells are not available from the existing databases. The wells on the County Well Index are shown on Figure 13-1. There are number ofnon-community supply wells adjacent to the study area. Most of these wells are related to commercial food processing that takes place in the area. None of these wells have Drinking Water Supply Management Areas (DWSMA) recorded at the Minnesota Department of Health. The nearest DWSMA is "Otsego East", located just west of the Mississippi River adjacent to the project area. This DWSMA is also shown on Figure 13-1. There are two primary groundwater sources in the Elk River Area: bedrock aquifers and unconsolidated sand and gravel aquifers. The Paleozoic sedimentary rocks around the Twin Cities Metro Area have three primary bedrock aquifers (in descending order): the Prairie du Chien-Jordan, the Franconia-Ironton-Galesville (FIG), and the Mt. Simon-Hinckley. Each of these is separated by a confining layer that essentially separates the aquifer. The Prairie du Chien-Jordan aquifer is the best producing bedrock aquifer in Minnesota. Elk River is located in a part of the region where this aquifer is absent, so it is unavailable for use by the City. This also means that development within the study area will have very little, if any, impact of this major water source. ' The shallowest continuous bedrock aquifer available to Elk River is the FIG. The FIG is the most commonly used aquifer for wells adjacent to the study area. The confining layer that usually occurs over the FIG is absent in most of the area and therefore, this ' makes the aquifer more vulnerable to contamination if the overlying sediments are highly permeable. The deepest of the three bedrock aquifers is the Mt. Simon-Hinckley. Elk River's supply wells all tap this aquifer for a combined total pumping capacity of 6,800 gallons per minute (gpm) (Wells 2-8). There are no geologic factors that would limit ' further use by Elk River. According to available records, none of the wells adjacent to the project area use this aquifer. ' The unconsolidated sand and gravel deposits in the Elk River area are aquifers that yield considerable volumes of water. Slightly less than half of the private wells adjacent to the study area are in one of these aquifers. Where there are wells finished in these unconsolidated sand and gravel deposits near the study area, special attention must be given to avoid contamination of these aquifers as they are often small and unconfined. ' City of Elk River Draft Alternative Urban Areawide Review July 2011 Page 33 of 84