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West Elk Mine 2007 Annual Hydrology Report 42 <br />• with pH values ranging from 7.92 to 8.58 and with average TDS concentrations ranging from about <br />2,482 to 3,126 mg/l (Table 10). <br />A salinity (TDS) loading analysis of the MCC's WY 2007 discharges was completed relative to the <br />current North Fork Cumulative Hydrologic Impacts Analysis (CHIS) (CDMG, 2003). The CHIS <br />analysis was conducted to assess the potential cumulative hydrologic impacts of mining and other <br />activities in the North Fork Valley on the North Fork's water quality and flow. The CHIS analysis <br />determined that no significant hydrologic impacts were expected as a result of mining activities at <br />the West Elk Mine. The CHIS assumed that MCC's contribution to the North Fork of the <br />Gunnison River would be a maximum of 5,520 gpm with a TDS concentration of 2,500 mg/1. <br />The total WY 2007 discharge from the Project, as reported from the CDPS reports, was <br />approximately 737.6 gpm (Table 10). Based on this value, the flow-weighted maximum annual <br />salinity (TDS) load from the Project was 3,076.1 tons. This represents about 9.3 percent of the <br />value used in the CHIS. The total WY 2007 discharge from the Project, as reported in the general <br />mine water balance for the Project is presented in Figure 8 and is estimated to be about 425 gpm <br />compared to the 737.6 gpm that was presented in the CDPS reports. Based on the mine water <br />balance value, the flow-weighted maximum annual salinity (TDS) load from the Project was 433 <br />• tons. This represents about 1.0 percent of the value used in the CHIS. A summary of the salinity <br />loading from the Project compared to the CHIS study is shown on Table 12. <br />Table 12 <br />Summary of Salinity Loading in the North Fork of the Gunnison <br /> Average Maximum Flow Calculated <br /> Continuous Weighted TDS Annual Salinity Percent of <br />Scenario Discharge Rate Concentration Loading CHIS Loading <br /> (gpm) (mg/1) (tons/year) <br />WY 2007 737.6 2246.7 3076.1 9.3% <br />WY 2007 (2) 425 169 433 1.0% <br />2003 CHIS (3) 5,520 2,500 30,159 - - <br />"I Using WY2007 CD PS DMR volumes <br />(2) Using WY2007 General Mine Water Balance Estimates and TDS values from the WY2007 DMR's <br />(3) Based on maximum permitted discharge rate <br />No mining induced impacts to water quality or flows in the North Fork are anticipated in WY <br />2008, because mine discharges are not expected to increase and the discharge water quality is <br />expected to remain the same. <br />• <br />June 2008 HydroGeo, Inc.