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Environmental Protection Plan, Schwartzwalder Mine 11-9 <br />(c) Ralston Creek Water Quality <br />Water in Ralston Creek upstream of the Schwartzwalder Mine is a calcium-bicarbonate type water, with <br />low levels of TDS (averaging 140 mg/L). Most metals are below detection at upstream monitoring stations <br />SW-UP, SW-UC, SW-AWD, and SW-A001 (Table 11-7, Appendix B). Uranium at upstream stations SW- <br />AWD and SW-A001 exceeded the water supply intake standard of 40 pCi/L or 0.059 mg/L (Figure 11-7) <br />only twice each since 199824. Uranium concentrations at upstream stations SW-AWD and SW-A001 have <br />never exceeded the instream aquatic toxicity standards. <br />Water quality in Ralston Creek changes with distance downstream of Stations SW-AWD and SW-A001, as <br />the creek flows across the mineralized zone and past the property. The alluvium and fill near the mine site <br />affect TDS and metals concentrations in the creek. The drinking water standard of 0.03 mg/L was <br />exceeded in 66 of 226 samples (29%) collected at the property boundary (SW-BPL) from January 1990 to <br />March 2010, prior to the startup of the new water treatment system in July 2010. The aquatic toxicity <br />standards for uranium and trace metals have seldom been exceeded, as shown in Table 11-6. At the <br />property boundary (Station SW-BPL), dissolved uranium has not exceeded the acute hardness-based <br />aquatic toxicity standards in any of 226 samples analyzed. Dissolved uranium at SW-BPL exceeded the <br />chronic toxicity standard in 1 of 226 samples. Total mercury exceeded chronic aquatic standards in two of <br />56 samples, dissolved iron in one of 68 samples, and total iron in two of 53 samples. Total aluminum <br />exceeded the chronic aquatic toxicity standard in 11 of 60 samples, while the acute standard was exceeded <br />only once. <br />Water quality in the creek has changed over time, as changes have occurred in discharge from the water <br />treatment plant, reclamation activities, sump pumping, and seasonal (low flow or high flow) conditions. <br />The changes in water quality over time are discussed in detail in Sections 11(c)(i) and 11(c)(ii) (during and <br />after operation of the water treatment plant, respectively). <br />• <br />24 AWD: 0.19 mg/L on 2/28/2001, 0.0897 mg/L on 1/20/2009; A001: 0.096 mg/L on 9/28/1998, 0.0897 mg/L on 5/29/2001 <br />4109C.100731 <br />Whetstone Associates