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West Elk Mine 2006 Annual Hydrology Report 41 <br />A salinity (TDS) loading analysis of the MCC's WY 2006 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. <br />The CHIS assumed that MCC's contribution to the North Fork would be a maximum of 5,520 gpm <br />with a TDS concentration of 2,500 mg/l. The total WY 2006 discharge from the Project, as <br />reported from the CDPS reports, was approximately 380 gpm (Table 10). Based on this value, the <br />flow-weighted maximum annual salinity (TDS) load from the Project was 2,107 tons. This <br />represents about 7.0 percent of the value used in the CHIS. The total WY 2006 discharge from the <br />Project, as reported in the general mine water balance for the Project as presented in Figure 3 was <br />estimated to be about 388 gpm, which is only 2 percent greater than that presented in the CDPS <br />reports. Based on this value, the flow-weighted maximum annual salinity (TDS) load from the <br />Project was 1,848 tons. This represents about 6.1 percent of the value used in the CHIS. A <br />summary of the salinity loading from the Project compared to the CHIS study is shown on Table <br />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 /> m m 1 tons/ ear <br />WY 2006 ~'1 380 2,362 2,107 7.0% <br />WY 2006 c2~ 388 3,025 1,848 6.1% <br />2003 CHIS t3> 5,520 2,500 30,159 - - <br />~'' Using WY2006 CDPS DMR volumes <br />(Z) Using WY2006 General Mine Water Balance Estimates and TDS values from the WY2006 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 />2007, because mine discharges are not expected to increase and the discharge water quality is <br />expected to remain the same. <br />5.2 Springs and Seeps <br />MCC routinely monitors 33 springs and seeps (Table 3). Hydrographs of spring and seep flows are <br />presented in Appendix D and the spring flow and water quality data are in Appendix E. <br />December 2007 HydroGeo, Inc. <br />