2012-10-01_REVISION - M1977284 (9)

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Mineral Joe Mine Environmental Protection Plan 10 nolybdenum, selenium, uranium, and vanadium compared to world shale and sandstone averages. The concentrations of uranium and vanadium in the Mineral Joe waste rock indicate that historical cutoff grades may have been higher, or ore control less accurate, than by current economic standards. For most metals, an abundance in the whole rock sample did not necessarily correlate with high leachate concentrations in the SPLP testing. The SPLP tests were performed by Energy Laboratories in accordance with EPA method 13 12 (EPA, 1994) and consisted of leaching the samples in a solution of weakly acidified deionized water for 18 hours. The extraction fluid was prepared by titrating a 60/40 weight percent mixture of sulfuric and nitric acids to deionized water until the pH was 5.00 (± 0.05). The solution and samples were then added to a sealed container in 20:1 ratios (solution:sample)' and tumbled for 18 hours at 30 rotations per minute (rpm) (± 2 rpm). The resulting solution was decanted, filtered (0.45 µm), and analyzed. SPLP results indicated that metal concentrations were below the detection limit in 75% (52 of 69) of the metals results for representative samples of Mineral Joe waste rock and JD -8 ore (Table 6). The Mineral Joe waste rock SPLP leachates met the Federal drinking water standards (maximum contaminant levels [MCLs], secondary maximum contaminant levels [SMCLs]), and Colorado domestic water supply standards for all metals except arsenic (0.042 mg/L), molybdenum (0.3 mg/L), and selenium (0.11 mg/L). Gross alpha activity in the SPLP leachate from the Mineral Joe waste rock composite sample exceeded MCLs by a factor of 20. Sulfate (737 mg/L) and TDS (1,240 mg/L)) exceeded secondary SMCLs by a factor of 3 and 2.5, respectively. Vanadium concentrations in the SPLP leachate exceeded the Colorado agricultural standard of 0.1 mg/L by a factor of 160. The representative ore pile SPLP leachates exceeded MCLs for arsenic, selenium, gross alpha, and fluoride, SMCLs for sulfate and TDS, Colorado drinking water standards for molybdenum, and the Colorado agricultural standard for vanadium (Table 6). Based on these results, the constituents of potential concern for the waste rock pile and ore pile are arsenic, molybdenum, selenium, gross alpha, sulfate, TDS, and vanadium. Further analysis was performed to determine whether or not these constituents would be mobile in the environment, based on site - specific precipitation rates, infiltration rates, and groundwater and surface conditions (Section 5.4.2). Samples for the core comparison were leached using a 2:1 ratio (solution:sample) to generate leachates with higher concentrations that could be more easily compared. 2 Federal drinking water standards, maximum contaminant levels, Colorado domestic water supply standards, and other standards discussed in Section 5.3.3 and 5.4.1 are used as screening levels to identify COPCs. These standards apply to groundwater in the environment and are not directly applicable to laboratory leachates. 4148B.120927 Whetstone Associates