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Hydrogeological Evaluation of Sunday Mines Group <br />Geologic and Hydrologic Conditions <br />approximately 40-60 feet based on available information. This reduces the hydraulic <br />gradient between the West Sunday Mine and the Dolores River, and lowers the <br />likelihood that mine water is currently flowing from the underground workings into <br />surrounding groundwater. <br />Groundwater use is also limited in a wider area surrounding the Sunday Group <br />Mines based on a search of the Colorado Division of Water and Natural Resources <br />well permit database. Several wells are currently permitted in an area near the <br />Dolores River southwest of the Sunday Group mines. These wells are listed in Exhibit <br />2.5 along with aliquot part legal descriptions of the well locations and the <br />approximate distance of the wells from the Sunday Group Mines. <br />The closest well to the Sunday Mines Group is a BLM stock well reported to be in the <br />Dakota aquifer. The well is located south of the Sunday Mines Group in the central <br />portion of Disappointment Valley. The Dakota aquifer is located stratigraphically <br />above the Salt Wash aquifer, which contains the underground mine workings. These <br />two aquifers are separated by a confining layer composed of bentonic shale of the <br />Brushy Basin member. Therefore, it is unlikely that water from the underground mine <br />areas would communicate with the Dakota Aquifer in this area. The development <br />rock area of the West Sunday mine overlies the Dakota aquifer in the Big Gypsum <br />Valley area on Figure 2-12. However, the Dakota aquifer in the Big Gypsum Valley <br />area is a fault bound block of Brushy Basin Formation and Dakota Sandstone, which <br />10 is not contiguous with the Dakota Aquifer in Disappointment Valley. The other wells <br />in the general area of the Sunday Group mines are located at extensive distances (i.e. <br />greater than four miles) and/or are upgradient from the mine areas. Information <br />regarding the depth of the wells is not available. <br />• <br />cm 2-26 <br />7:\64988-Denison Mines\Task Order 3 - DMO Sampling and Analysis Plan\Task 3.14 - Hydrogeology ReportVinal sunday hydro reporNextTINAL Sunday Hydrogeology Report.doc