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Schwartzwalder Mine -Hydrologic Evaluation of Mine Closure and Reclamation 50 6.4 Potential Loading Sources 6.4.1 Upgradient Sources The water quality in Ralston Creek is affected by upgradient sources, including the Mena and Northstar Mines. Neither of these properties have been owned or operated by Cotter Corporation. The flow conditions and water quality from the Mena Mine were investigated in 1999. The Mena Mine is located approximately 2 miles upstream of the Schwartzwalder Mine. The Mena Mine shaft is 50-90 feet deep. The mine consists of a north drift and a south drift, each of which extends 100-200 ft. The water level in the Mena mine has at times reached creek level, but is often 15-20 feet below the portal. Water quality samples have been collected in the creek downstream and upstream of the mine, and in the mine shaft itself. These data indicate that total uranium increases very slightly from upstream to downstream, while dissolved uranium concentrations in the creek are unaffected by the mine. The concentrations of most other parameters in the creek, including total alkalinity, pH, conductivity, TDS, Ca, Mg, Cl, and NH4, are apparently not significantly affected by the Mena mine. Slight decreases in sulfate and iron and increases in TSS are apparent. The sampling results are provided in Appendix F. 6.4.2 Alluvium and Fill Four sumps were operated in the alluvium and fill adjacent to Ralston Creek (Figure 10). The sumps operated from 1990 to June 2002, and were designed to limit direct seepage of uranium-impacted water from the alluvium into the creek. During operation, the sumps were effective in reducing uranium loading to Ralston Creek because alluvial groundwater with higher concentrations of uranium and other dissolved solids was drawn into the sumps and prevented from interacting with water in the creek. The effect of groundwater in the alluvium and valley fill on water quality in Ralston Creek was evident when the sumps were shut down. Two short-duration sump shutdown tests were conducted in 1998 and 1999, and the sumps were permanently shut down in June 2002. The sump shut down tests (Appendix G) indicated that water quality in Ralston Creek would be affected after the sumps were permanently shut down. The permanent shutdown of the sumps resulted in an initial flush of higher concentrations, which have generally decreased over time as described in Section 6.5.2. 6.4.3 Mineralized Bedrock Naturally mineralized bedrock is an additional potential source of loading to Ralston Creek. In addition to potential contributions from upgradient mines listed in Section 6.4.1, Ralston Creek flows across the mineralized Illinios Fault zone upstream of the Schwartzwalder's Pierce and Steve Adits and other mineralized areas downstream of the mine property. Radiometric readings in the area drained by Ralston Creek are shown in the USGS map prepared by E.J. Young (1985) (Figure 27). Whetstone Associates • 4109B.071116