2010-08-02_REVISION - M1977300 (25)

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Environmental Protection Plan, Schwartzwalder Mine 11-10 0 Table 11-6. Comparison of Water Quality in Ralston Creek to Aquatic Toxicity Standards • Parameter Units Summary Statistics Aquatic Standards (based on average Number of Exceedences hardness a t SW-BPL) # of Samples # of ND % ND Acute Chronic # of Acute # of Chronic pH S.U. 32 0 0% 6.5-9.0 6.5-9.0 1 0 Nitrate Nitrogen mg/L 10 3 30% 10 10 0 0 Ammonia, total mg/L 10 10 100% 22.8 5.77 0 0 Sulfate mg/L 79 0 0% 250 250 1 1 Chloride mg/L 78 0 0% 250 250 0 0 Aluminum, total mg/L 60 47 78% 0.75 0.087 1. it* Arsenic, total mg/L 59 59 100% 0.05 --- 0 --- Boron, total m 3 3 100% 0.75 0.75 0 0 Cadmium, dissolved mg/L 6 6 100% 0.0026 0.00061 0 0 Chromium, dissolved mg/L 6 6 100% 0.016 0.011 0 0 Cyanide, total mg/L 1 1 100% 0.005 0.005 0 0 -Copper, dissolved mg/L 83 71 86% 0.0213 0.0136 0 0 Iron, dissolved mg/L 68 45 66% --- 0.3 --- 1 Iron, total mg/L 53 12 23% --- 1 --- 2 Lead, dissolved mg/L 8 8 100% 0.1095 0.00427 0 0 Lead, total mg/L 59 59 100% 0 0 Manganese, dissolved mg/L 80 68 85% 3.513 1.941 0 0 Manganese, total mg/L 59 39 66% Mercury, total mg/L 56 54 96% --- 0 --- 2 Nickel, dissolved mg/L 8 8 100% 0.7079 0.0786 0 0 Selenium, dissolved mg/L 8 8 100% 0.0000184 0.0000046 0 0 Silver, dissolved mg/L 9 9 100% 0.0047 0.00074 0 0 Thallium, dissolved mg/L 85 85 100% --- 0.015 --- 0 Zinc, dissolved mg/L 10 8 80% 0.2174 0.1885 0 0 Uranium, dissolved mg/L 226 0 0% 4.116 2.571 0 1 Uranium, suspended mg/L 74 35 47% 4.116 2.571 0 0 Uranium, total mg/L 6 0 0 4.116 2.571 0 0 Radium-226, dissolved pCi/L 90 15 17% 5 5 0 0 Radium-226, suspended Ci/L 63 51 81% 5 5 0 0 * Aluminum standard based on total recoverable concentrations Table based on data from October 1998 - March 2010, except dissolved uranium which is based on data from Jan 1990 - March 2010 Comparison to uranium drinking water standards is provided in preceding text. (i) Water Quality During Operation of the Sumps and WTP While the sumps and water treatment plant were operating, the TDS in Ralston Creek increased to about 250 mg/L and the water changed to a calcium-magnesium-sodium-bicarbonate water as Ralston Creek flowed past the mine site (Figure 11-1). TDS concentrations varied seasonally (Figure 11-2), and were generally highest during the winter months and lowest during the spring months. Bicarbonate and sulfate were the dominant components of TDS in Ralston Creek adjacent to and below the mine site (Figure 11-2). Sulfate concentrations averaged 20 mg/L upstream of the mine and 68 mg/L downstream of the mine, and did not exceed the water quality standard of 250 mg/L in any of the samples analyzed. The shift from a calcium-bicarbonate type water to a calcium-magnesium-sodium-bicarbonate type water was evident in the Piper diagram of average water quality at 14 stations (13 stations in Ralston Creek plus the treatment plant discharge.) Stations SW-UP, SW-UC, SW-AWD, and SW-AO01 plot in a single cluster in the cation field of the Piper diagram (Figure 11-3), while stations SW-BDIS, SW-OS, SW-BOS, SW- GS, and SW-LLHG plot in separate cluster. The discharge water (Station SW-DIS001) had lower calcium and higher sodium than the upstream and downstream waters (Table 11-7). Minor ions and trace metal concentrations remained essentially constant upstream and downstream of the mine, with the exception of uranium and molybdenum. Most trace metals were below detection at all sample stations. Uranium increased from about 0.003 mg/L upstream of the mine to about 0.006 mg/L near • the downstream property boundary (Table 11-8), well below the drinking water intake standard of 0.059 mg/L (40 pCi/L) and the hardness-based aquatic toxicity standards. Molybdenum increased from below 4109C.100731 Whetstone Associates