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Section 8 <br />Groundwater Quality <br />laterally within the sandstone unit. Vertical flow is restricted by interbedded low <br />permeability units such as the intermediate siltstones and shales of the Salt Wash <br />Member, which limits potential vertical migration of groundwater. The groundwater <br />quality data described above show a marked difference in groundwater quality <br />between the units. Groundwater quality in the Top Rim Sandstone displays a <br />signature associated with the enrichments of uranium, vanadium and other elements <br />that are enriched in the ore bodies. Water quality from the underlying unit displays a <br />different chemistry with very high salinity. This suggests that the intermediate <br />siltstones and shales of the Salt Wash Member may contain enrichments of sodium, <br />chloride and sulfate. <br />The groundwater quality data collected to date shows that groundwater located <br />within approximately 40 feet of the underground workings shows a characteristic <br />signature associated with the natural enrichments of uranium, vanadium and other <br />elements that comprise the ore bodies. This signature does not extend even locally <br />into the underlying intermediate siltstones and shales of the Salt Wash member. The <br />lateral extent of groundwater with this characteristic chemical signature in the Top <br />Rim Sandstone unit is currently unknown. Denison intends to continue collecting <br />groundwater quality data from the wells for a period of at least four quarters to <br />further define the ambient groundwater condition. In addition, two proposed <br />monitoring well will be installed along the perimeter of the permit boundary as <br />discussed later in Section 11 - Water Quality Monitoring Plan. <br />• 8.3 Existing and Future Uses of Groundwater <br />Existing or potential future uses of groundwater within 2 miles of the Sunday Mines <br />Group are limited because the land is primarily public land administered by the BLM. <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. Currently, approximately 400 gallons per day of groundwater is pumped from <br />the base of the West Sunday Mine to several areas within the Sunday Mines Group <br />Complex (Stanley Davies, West Sunday Mine Superintendant, personal <br />communication 2008). Although the available groundwater volume is low <br />(approximately 0.3 gallons per minute), it is currently sufficient to supply needs for <br />the underground mining operations. <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 />C7 <br />8-5 <br />TA64986-Denison MineslTask Order 4 - EPP Sunday Mines GroupTINAL EPPtFINAL - Environmental Protection Plan Sunday Mines.doc