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information to Support D0171SO17 BLMEnuironmenla /Assessment Remand <br />Denison Sunday Mhes Group <br />process. Uranium and several other trace elements that are naturally <br />enriched in the ore body are somewhat more soluble under oxidizing <br />conditions as a result of ventilation, and the water quality within the <br />mine may reflect water -rock interactions and the influence of ventilation. <br />However, available literature also indicates that natural groundwater <br />quality is likely poor in the direct vicinity of the uranium and vanadium <br />ore bodies (CDM 2009b). <br />As discussed previously, Denison is currently working with DRMS to <br />develop an environmental protection plan that will minimize potential <br />for the mines to adversely affect groundwater quality, and to monitor <br />potential effects through installation of groundwater monitoring wells. <br />As discussed previously, recovery of the water table within the <br />underground workings is very slow (available data suggest that the water <br />table has not recovered in approximately 20 years since dewatering <br />ceased in about 1990). In addition, the rate of groundwater flow in the <br />Salt Wash aquifer is very slow. These factors suggest that the <br />groundwater will return to the natural more reducing conditions before it <br />flows a significant distance from the mines. Although these natural <br />conditions mitigate the potential for mining operations to cause <br />significant effects to groundwater quality, Denison is developing further <br />mitigation to reduce the potential for the mines to adversely affect <br />ground water quality. These mitigation plans include installation of air <br />seals within the underground workings and closing vent holes at the time <br />of mine closure to further restrict inflow of oxygenated air into portions <br />of the mine that will eventually be saturated when the water table <br />recovers decades after mining ceases. These actions will further mitigate <br />the potential for the mines to affect water groundwater quality. <br />References <br />CDM Inc. (CDM). 2008. Final Development Rock, Ore, and Soil Clxaracterization Data <br />Collection Work Plan, to Address Designated Mining Operations (DMO) Status Sunday Mines <br />Group and Van 4 Mine, San Miguel County. July. <br />CDM. 2009a. Environmental Geochemistry Investigation of Rock and Soil Material, Sunday <br />Mines Group. May. <br />CDM, 2009b. Hydrologic Evaluation of the Sunday Mines Group. May. <br />U.S. Bureau of Land Management (BLM). 2009a. Colorado State Directors Office Remand <br />Decision for Topaz and Sunday mine EA, FONSI, RD and PO, September 17. <br />BLM. 2009b. Written correspondence regarding remand decision for Topaz and Sunday mine <br />EA, FONSI, RD and PO from Dolores Public Land Office to Denison Mines (USA) Corp, <br />November 3. <br />Final Sunday Mines BLM Remand Letter.doc <br />