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5 <br />5.1.2 <br />Groundwater Availability <br />The City of Ramsey currently utilizes groundwater as its exclusive source of drinking water. For <br />planning purposes, the City needs to understand whether groundwater can continue to provide <br />existing and future water demands. <br />Description of the Hydrogeological Setting <br />The following sections describe the hydrogeology (groundwater) in Ramsey. <br />Surficial Hydrogeological Setting <br />The surficial geology in the region is primarily associated with erosional and depositional glacial <br />events during the Quaternary Period. Surficial aquifers throughout this region have highly <br />variable aquifer properties. The Metropolitan Council classifies these as having a moderate to <br />high water yield for potable use; however, it is often challenging to identify the locations for the <br />most productive units with some areas providing little or no yield for water supply. Depending on <br />the location, the presence of finer grained units that can act as confining layer will affect water <br />recharge rates to these aquifers and limit the quantity of water these aquifers can supply. <br />Surficial aquifers are often the first aquifer to be recharged and thus can be more vulnerable to <br />contamination. Therefore, the overall water quantity and quality is described by the Metropolitan <br />Council as variable. <br />Bedrock Hydrogeologic Setting <br />The bedrock underlying the City of Ramsey and surrounding areas consists of Precambrian to <br />Ordovician age Paleozoic sedimentary strata overlying Precambrian age basement rock. While <br />variation and extent of bedrock aquifers occur, in general five regional aquifers are described and <br />support much of the potable water for the Twin Cities region, from oldest to youngest: (1) Mt <br />Simon -Hinckley (2) Tunnel City-Wonewoc (3) Prairie du Chien -Jordan (4) St. Peter, and (5) <br />Quaternary aquifers. These aquifers are hydrologically disconnected by a variety of interbedded <br />confining layers. Regional aquifers can also be subdivided further; for example, the Tunnel City- <br />Wonewoc Aquifer maybe be hydraulically disconnected if the Lone Rock Formation (of the <br />Tunnel City Group) acts as a confining unit. Primary lithology, and hydrogeologic designations <br />are summarized in the table below, from oldest to youngest, for the area. <br />FEASIBILITY STUDY RAMSY 154354 <br />Page 14 <br />