2011-03-29_REVISION - M1977493 (4)

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• Water Ouality ??b? erg-ors I ? 77- f ?3 Section 6 discusses groundwater flow through the mine site. CMC claims that the direction of groundwater flow is controlled by bedrock topography, but is coincident with the surface water drainages. Please provide the following data, if available, so that we may better assess potential path and impacts from groundwater flow: water level data, geological mapping, predictive groundwater modeling, potentiometric surface, and any slug/permeability or pumping tests from the site. Any ground water quality sampling data or analysis should also be provided. During Phase I, CMC is proposing to raise the impoundment for the Ten Mile TSF by 28 feet. We are concerned that the increase in head may lead to increased seepage and impacted water could flow into the Eagle Park Reservoir as surface water runoff or groundwater inflow. Additional sampling below the northwest toe of the 2 Dam may be necessary. Are the systems in place capable of handling increased seepage from raising the Tenmile TSF dam? CMC appears to be expanding Robinson Lake. From our initial review, it did not look as though the dam elevation would be raised, although the pool elevation will be raised. Are the seepage pumping facilities in place capable of handling increased seepage from the Lake? Is the Robinson Lake seepage collection pond lined? If not, what about seepage from the seepage pond from a water quality standpoint? Clearly, there were elevated levels of some metals downstream of the seepage collection pond at the time of sampling for the groundwater management plan. • Samples included in Appendix C of Exhibit T for the Eagle Valley Monitoring Well (EVMW), exceed water quality criteria for water supply for iron, manganese, sulfate, chloride. Additionally, cyanide concentrations were elevated slightly at the time of the original TR-08 Groundwater Monitoring Plan. The highest recorded iron sample was 1.74 mg/L (1,740 ug/L). The water supply criteria for Segment 14 of the Eagle River is 300 ug/L (dissolved). The highest recorded manganese sample was 0.68 mg/L (680 ug/L). The water supply criteria for Segment 14 is 50 ug/L. The highest recorded sulfate sample was 790 mg/L (7,900 ug/L). The water supply criteria for Segment 14 of the Eagle River is 250 ug/L. Due to the elevated metals, and the timing of previous sampling, additional monitoring should be done during active mineral extraction and possibly for some time after to ensure that water quality from Robinson Lake seepage or Tenmile TSF seepage will not impair water quality in the Eagle Park Reservoir. A water quality monitoring plan should include all parameters for which it can reasonably be assumed that water quality (groundwater and surface water in the Eagle Park Reservoir) may be impacted. Please calculate the water quality standards for all metals listed in Regulation 33, including hardness based metals table value standards. The data included in Appendix C to Exhibit T did not include sampling data for As, CrIII, CrVI, Hg, Ni, or Se, which are current water quality standards for Segment 14 of the Eagle River. Additional non-metallic samples should include Dissolved Oxygen, E. Coli, Ammonia, Sulfur, Boron, Nitrite, Nitrate, and Chlorine. Water quality in the East Interceptor Ditch may be impacted by runoff contact with overburden storage in the McNulty OSF. • Section E-12 (Reclamation Monitoring and Success Standards) does not include any discussion of water quality monitoring. IIRECEIVED ?MAR 2 9 ?011 pivtsien of Roe4am#w, -?79 MiR