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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> parameters of gross alpha, gross beta, and radium-226 and radium-228. Colorado BSGWs are <br /> 0.0168 to 0.03 mg/L (domestic water supply or DWS) for uranium, 15 pCi/L (DWS)for gross <br /> alpha, 4 millirem/year(DWS) for gross beta, and 5 picoCuries per liter(pCi/L) (DWS) for radium- <br /> 226 and radium-228. Vanadium has an agricultural standard of 0.1 mg/L. There is no <br /> groundwater DWS or human-health (HH) based standard for vanadium. <br /> As Tables 10-3, 10-4 and 10-5 illustrate, uranium, vanadium and gross alpha are exceeded at 8 <br /> 10, and 12 times, respectively, in 12 samples at MW-SUN1; uranium and gross alpha are <br /> exceeded 5 and 10 times, respectively, in 10 samples for well MW-SUN2, and gross alpha is <br /> exceeded 5 times in 12 samples for well MW-SUN3. Uranium concentrations increase <br /> downgradient with the highest concentrations (0.21 mg/L) in well MW-SUN1. Well MW-SUN2 <br /> showed 4 samples that were just above the HH standard of 0.01 mg/L for arsenic and arsenic <br /> standards were also exceeded for the underground mine samples, the highest of which (3.87 <br /> mg/L)was from one of the Top Rim wells installed by Denison in the West Sunday mine. <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 because these <br /> elements are naturally high in the mineralized portions of the Salt Wash. Underground wells <br /> WS-2 and WS-3 had the maximum uranium concentrations of all underground groundwater <br /> samples at 9.15, and 1.65 mg/L over two sampling dates in 2009 (CDM and Denison, 2012). <br /> The uranium levels in well WS-4, screened in an underlying unit of siltstone and mudstone, <br /> were just above the lower DWS of 0.0168 mg/L. Vent shaft S-8 did not exceed any radiological <br /> standards. <br /> Groundwater at upgradient (ambient) well MW-SUN3 has the lowest TDS concentration of all <br /> samples taken followed closely by MW-SUN2 and S-8. However, MW-SUN2, as mentioned, is <br /> likely influenced by perched water zones in the Brushy Basin Member, and water levels in vent <br /> shaft S-8 may also be influenced by groundwater infiltration from the overlying Burro Canyon <br /> Formation and Brushy Basin member of the Morrison Formation. The characteristically low TDS <br /> at well MW-SUN3 is mostly due to the relatively low total alkalinity. MW-SUN3 water does not <br /> exceed any BSGWs except once for iron, and 5 times for gross alpha, and once for combined <br /> 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. With exception of S-8, all underground mine <br /> Western Water& Land, Inc. 48 <br />