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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> Water Chemistry <br /> • Water chemistry baseline data from the monitoring wells show MW-SUN1 groundwater is of <br /> a sodium-potassium sulfate type, and groundwater of wells MW SUN2 and MW-SUN3 are of <br /> a sodium-potassium bicarbonate type. <br /> • Monitoring wells show a decrease in water quality from the upgradient well to the <br /> downgradient well, as to be expected along a groundwater flow path. <br /> • Within the surface monitoring wells, uranium, vanadium and gross alpha are exceeded 8, 10, <br /> and 12 times, respectively, in 12 samples at MWSUN-1; uranium and gross alpha are <br /> exceeded 5 and 10 times, respectively in well MW-SUN2, and gross alpha is exceeded 5 <br /> times in well MW-SUN3. Uranium concentrations increase downgradient, that is, from <br /> northeast to southwest, with the highest concentrations in well MW-SUN1. <br /> • Groundwater at MW-SUN3 has the least saline composition of all samples. MW-SUN3 water <br /> does not exceed any BSGWs except once for iron, 5 times for gross alpha, and once for <br /> combined radium-226 and radium-228. The MW-SUN3 groundwater has the lowest uranium <br /> concentrations but the highest gross alpha, gross beta, radium-226, and radium-228 <br /> concentrations of the three monitoring wells. <br /> • The underground wells installed by Denison in 2009 in the West Sunday Mine indicate how <br /> water chemistry can vary dramatically from strata to strata within the Salt Wash Member in <br /> the West Sunday Mine. The wells screened in the Top Rim Sandstone unit contained <br /> arsenic, molybdenum, uranium and vanadium concentrations magnitudes greater than the <br /> well screened in the siltstone unit. The well screened in an underlying siltstone and mudstone <br /> were consistently greater in concentrations in major ions and metals compared to the Top <br /> Rim wells. <br /> • Underground mine samples, with the exception of the S-8 vent shaft, had the highest <br /> concentrations of uranium, vanadium, gross alpha, and gross beta. This is understandable <br /> because these elements are naturally high in the mineralized portions of the Salt Wash and <br /> mining of these zones increases overall exposure of these materials to groundwater inflow. <br /> A hydrogeologic conceptual model was developed using available information from past SMC reports <br /> and the new data acquired for this study. The hydrogeologic conceptual model applies to the <br /> occurrence and flow of groundwater in the Top Rim unit of the Salt Wash Member, but since the <br /> geologic continuity of the Top Rim is not known, the model applies to the Salt Wash Member in <br /> general. <br /> Western Water& Land, Inc. 54 <br />