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10/4/10 <br />COTTER CORPORATION (N.S.L.) <br />PROPOSED EXPANSION OF ALLUVIAL GROUNDWATER EXTRACTION SYSTEM <br />Background and Rationale <br />On July 30, 2010, Cotter Corporation (N.S.L.) ("Cotter") began operating a nominal 100-gpm <br />water treatment system to treat alluvial groundwater reporting to Sump 1 at the Schwartzwalder <br />Mine site. This remedial activity was authorized by the Division of Reclamation, Mining &'. <br />Safety (DRMS) through partial approval of Technical Revision (TR) 12 to Permit M-300-1971 <br />(DRMS, July 8, 2010). It was also authorized by the Water Quality Control Division (WQCD) <br />through an amendment to Notice of Violation/Cease and Desist Order 10-00601 -1 (WQCD, July <br />29, 2010). <br />Results of water quality monitoring performed along Ralston Creek during the first few weeks <br />following initiation of pumping and treatment of groundwater reporting to Sump No. 1 suggested <br />that the groundwater extraction system should be expanded as soon as possible to increase <br />groundwater capture and treatment from other portions of the alluvial fill. Cotter procured and <br />installed the necessary equipment and began pumping and treating water from Sump 4 on August <br />16, 2010, and from MW 9 on August 19, 2010. <br />Total flow rate from the three extraction points has averaged approximately 84 gpm. Through <br />September 13, 2010 groundwater extraction and treatment systems at the site have removed <br />approximately 130 pounds of uranium from alluvial groundwater (Figure 1). A significant <br />increase in the rate of uranium removal occurred after the pumping system was expanded to <br />include Sump 4 and MW 9. <br />Water quality monitoring data indicate that the capture and treatment system to date has <br />significantly reduced uranium loading in Ralston Creek. Mass flow calculations of uranium in <br />pounds per day measured at monitoring station SW-BPL (just below the property line) show the <br />lowest daily mass flow of uranium in the creek since late 2008 (Figure 2). However, during low <br />stream flow conditions, concentrations at SW-BPL have still exceeded the 0.03 mg/L uranium <br />stream standard. Based on monitoring data and a targeted site inspection (conducted during; <br />minimal annual stream flow conditions), the reason for this result has become clear and has led <br />to the proposed supplemental mitigation strategy which offers the potential to rapidly and <br />significantly further improve water quality conditions in the creek, even during negligible stream <br />flow conditions.