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Daniel Arnold, Esq. January 25, 2011 <br />Denver Water Page 15 of 21 <br />calcium and . bicarbonate, will serve to stabilize uranium in the dissolved form (as the <br />carbonate and calcium carbonate complexes); these forms require a more strongly <br />reducing environment in order to promote the formation of insoluble, reduced uranium <br />minerals. <br />Also, if the mine pool rises a few more feet, it will intersect upper workings along the <br />Steve adit that are not currently flooded. These workings include: ILLRS, 146, and <br />WASH and water samples from these workings are reported to contain uranium <br />concentrations of 150, 130, and 52 mg/L, respectively. These concentrations are greater <br />than the current mine pool concentration of approximately 34 mg /L. Based on this <br />information, future inflow to the mine pool is likely to be enriched in dissolved uranium. <br />3.5 Bedrock Aquifer <br />EPP Finding: Bedrock is not an aquifer based on its minimal yield of water to wells. <br />The bedrock at the mine has been hydraulically tested and has an overall low <br />permeability on the order of 0.0003 feet /day, which is representative of competent <br />bedrock. The fractured bedrock has a higher hydraulic conductivity and contains water in <br />usable amounts to wells and the claim that the bedrock is not an aquifer is misleading. <br />Table 8 -2 of the EPP identifies registered wells within a 2 -mile radius of the mine. Over <br />100 bedrock wells are identified with well yields ranging from 1 to 55 gpm, typically <br />averaging between 5 to 10 gpm. From 1995 and 1999, the EPP reports that the average <br />inflow to the mine when it was dewatered was 189 gpm, suggesting that the bedrock can <br />yield appreciable amounts of water. The yield to individual bedrock wells is sufficient <br />making the bedrock a usable aquifer. <br />EPP Finding: Background uranium concentrations range from 0.0013 to 2.63 mg /L <br />based on samples collected from well MW -11, which is a bedrock well located above <br />the mine. <br />Well MW -11 is 200 feet deep and is paired with MW -10 that is 75 feet deep. The shallow <br />bedrock well is reported to be contaminated with cement grout that has entered the well <br />screen. Well MW -11 has been sampled and is reported to also be contaminated with <br />cement grout in 2009. Background uranium values that span three orders of magnitude <br />are suspect and given the known grout contamination in MW -11 the uranium <br />concentrations are highly suspect and background conditions have not been adequately <br />defined. <br />Data Adequacy: Because of the suspect data from well MW -11, the mine has no reliable <br />background groundwater data. Furthermore, there are no wells completed in the upper <br />portion of the bedrock along the valley floor to characterize bedrock water quality. <br />Considering that the mine pool is now 10 to 30 feet above the valley floor, bedrock <br />groundwater between the mine pool and the creek should be characterized. <br />