2010-05-07_PERMIT FILE - C2009087 (6)

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Arsenic - The average arsenic value for the 10 samples analyzed was less than the analytical method detection limit of 0.2 mg/kg. The method detection limit is below suitability criteria established by • the WDEQ. No adverse impacts associated with arsenic are anticipated. Iron - The average iron concentration of the samples analyzed was found to be 4.49 mg/kg, with a range of 2.7 to 7.2 mg/kg. These concentrations are in contrast to the nearby Twentymile Mine where iron concentrations are one to two magnitudes higher. This indicates a marked decrease in the potential for iron to be an aquifer restoration concern. Elevated total iron concentrations in surface water samples collected from Grassy Creek during periods with elevated total suspended solids have been noted as possibly being related to Seneca II Mine spoils. However, the combination of the low overburden iron concentrations, low hydraulic conductivity of surrounding rock units, and the separation distance between the proposed PSCM workings and surface water features minimizes potential water quality impacts to surface water and adjoining aquifers. In addition, surface water treatment facilities are being planned for the PSCM to mitigate the potential for elevated iron concentrations to impact surface water bodies. Water quality considerations are more fully addressed under Section 2.05.6, in the Probable Hydrologic Consequences section. Lead- The average lead concentration of samples analyzed was 0.24 mg/kg with a range of 0.2 to 0.6 mg/kg. The suspect level of lead, according to the Montana Department of State Lands, is between 10 and 20 mg/kg. Since none of the lead values approach the minimum suspect level, no lead- associated problems are anticipated. Manganese - The average soluble manganese concentration of the samples analyzed was found to be 1.71 meq/L, with a range of 0.15 to 9.01 meq/L. The extractable manganese concentration average • was 0.32 mg/kg. The detected concentrations represent low concentrations, below those found in mine workings at the Twentymile Mine. Since all values are well below the minimum suspect level, it is highly unlikely that manganese- related problems would occur. Molybdenum- All of the molybdenum values were below the laboratory detection limit of 0.05 mg/kg. Given the uniformly low values, it is unlikely that molybdenum poses any potential environmental problem. Zinc - The average zinc concentration of the samples analyzed was 0.57 mg/kg, with a range of 0.24 to 0.93 mg/kg. The detected concentrations represent low concentrations, a magnitude below those found in roof and floor units at Twentymile Mine. It appears unlikely that zinc would pose a problem relative to reclamation or water quality. Mercury — Approximately half of the samples analyzed were below the laboratory detection limit of 0.02 mg/kg. The average detected concentration was 0.06 mg/kg. The level of mercury detected is low and it is unlikely that mercury will pose an environmental problem. Sulfur - Three forms of sulfur were analyzed in order to predict the potential for development of acid - forming conditions in either coal refuse or the gob. The sulfur analysis values are uniformly low. Considering the low values and the buffering capacity of the other chemical constituents in the roof and floor strata, the potential for development of acid - forming conditions is low. At the adjacent Seneca II Mine the spoil wells have demonstrated a neutral to slightly basic pH following re- saturation giving an indication of what to expect at the PSCM. Complete chemical analyses of the Wadge Seam are presented in Exhibit 2.04.6 -E2, Geologic Information — Lithologic and Geophysical Logs (confidential). Data from the following drill holes PSCM Permit App. 2.04 -32 6/15/09