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Schwartzwalder Mine -Hydrologic Evaluation of Mine Closure and Reclamation 45 <br /> C(acnte> -WER • em,t•~n(H)+bA v, <br />L1/i <br /> _ moln(Fl~+hc <br />C(chronic> - WER ~ e • KC <br />where WER= Water effect ratio <br />mA = Metal-specific constant for acute toxicity (e.g, mA for uranium is 1.1021) <br />m <br />= Metal-specific constant for chronic toxicity (e.g, m~ for uranium is 1.1021) <br />~ <br />H = Hardness (mg/L as CaCO3) <br />bA = Metal-specific constant for acute toxicity (e.g, bA for uranium is 2.7088) <br />b~ = Metal-specific constant for chronic toxicity (e.g, b~ for uranium is 2.2382) <br />K = Freshwater conversion factor <br />The numeric criteria shown in Table 21 have been calculated based on a hardness of 163, which is the low- <br />flow average at station SW-BPL since sump shut-off in June 2002. The calculation assumes a water effect <br />ratio (WER) of 1.0 unless otherwise noted. <br />The uranium standard of 40 pCi/L (0.059 mg/L) applies at a water supply intake. Elsewhere, the hardness- <br />based aquatic toxicity standards apply. Using a hardness of 163 mg/L, the acute toxicity standard for <br />uranium is 4.12 mg/L and the chronic toxicity standard is 2.57 mg/L. <br />The hardness value used in calculating numeric criteria is the average of the calculated hardness values for <br />station SW-BPL during low flow months from June 2002 to February 2007. The use of average of <br />hardness values during low-flow season is in accordance with the CDPHE WQCCs "Basic Standards and <br />Methodologies for Surface Water," Document 5 CCR 1002-31, Table III, footnote (3). At Station SW- <br />BPL, the low-flow season occurs between July and February. Hardness values were calculated from <br />magnesium and calcium concentrations, and the calculated values were similar to laboratory-determined <br />hardness values, when reported by the lab. Because values for many analytes, including calcium and <br />magnesium, were different before and after the sump shut-off, only data from post sump shut-off were used <br />to determine the mean hardness value used in the numeric criteria calculations. Calculated hardness values <br />for these distinct periods are presented in Table 20. <br />4109B.071116 Whetstone Associates <br />