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Section 8 <br />Groundwater Quality <br />The only current groundwater use in the area is an industrial use to support Denison <br />Mining operations, which is permitted by a Colorado Well Permit. <br />Groundwater use in conjunction with mining activities is limited to small quantities of <br />water used for drilling and dust suppression purposes within the underground <br />mines. During previous mining activities, approximately 400 gallons per day of <br />groundwater was pumped from the base of the West Sunday Mine to several areas <br />within the Sunday Mines Group Complex (Stanley Davies, West Sunday Mine <br />Superintendant, personal communication 2008). Although the available groundwater <br />volume is low (approximately 0.3 gallons per minute), it was sufficient to supply <br />needs for the underground mining operations. Mine dewatering activities ceased in <br />June 2009; since that time, the mine has been in temporary cessation status. <br />Although the rate of groundwater use in the West Sunday mine is relatively modest, <br />it has lowered the water table in the vicinity of the underground workings by <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 Mines <br />Group 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 Mines Group. These wells are listed in Exhibit <br />8 -1 along with aliquot part legal descriptions of the well locations and the <br />approximate distance of the wells from the Sunday Mines Group. <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 8 -2. 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 />is not contiguous with the Dakota Aquifer in Disappointment Valley. The other wells <br />in the general area of the Sunday Mines Group 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 />C \Users\cwoodward\Desktop \Sundays \FINAL - Environmental Protection Plan Sunday Mines Revised January 2012 docx <br />8 -6 <br />