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November 12, 2010 2 of 6 <br />the 1999 - 2000 hydrology study indicated losing reaches of Ralston Creek near station SW-OS, <br />recent water quality data and observations in excavation trenches clearly show that the creek loses <br />water to the alluvium and fill at and above station SW-OS, and gains water from the alluvium near <br />and below station SW-BOS (Figure 3). The location of the historical (1938) stream channel <br />influences flow directions, as does the constriction of the valley near Sump 1 and the choke point <br />(where all water in the alluvium is forced into the creek) above SW-BPL. This refined <br />information on flow directions and flow rates in the alluvium has been used to strategically locate <br />two new sumps, Sump 5 and Sump 8, to intercept groundwater before it. reaches Ralston Creek. <br />Operation of these sumps will lead to improvements in water quality in Ralston Creek. <br />Sump 5 and Sump 8 are planned to improve the hydraulic capture efficiency of alluvial <br />groundwater. The locations of these sumps were strategically selected based on information <br />gathered during the first three months of treatment system operation. Sump 5 was constructed <br />from November 3, 2010 to November 9, 2010 and began operating on November 11, 2010, and is <br />expected to further lower uranium concentrations in Ralston Creek. <br />Water quality in the alluvium exceeded the 0.03 mg/L uranium standard before the mine pool ever <br />reached the level of the alluvium. This indicates that sources of loading exist in the alluvium and <br />fill, independent of any potential influence from the mine pool. Cotter is investigating sources of <br />loading to the alluvium as described in the request for Technical Revision 14, and will identify the <br />appropriate mitigation strategies for the fill material. Until those sources are identified and <br />removed, the groundwater capture and treatment system will reduce impacts from the alluvium <br />and fill on water quality in Ralston Creek. <br />The focus of the remediation activities is, and should be, the minimization of loading to Ralston <br />Creek. The sump collector system is intended to intercept water from sources in the alluvium or <br />any sources from the mine pool before it reaches Ralston Creek. The ion exchange treatment <br />system has been successful in reducing discharge to below the 0.03 mg/L uranium standard. The <br />expansion of the sump collector system is expected to improve the hydraulic capture of alluvial <br />groundwater and eventually meet water quality standards in Ralston Creek. <br />REFERENCES <br />Whetstone Associates, 2010. Schwartzwalder Mine Environmental Protection Plan, prepared for <br />Cotter Corporation, July 31, 2010.