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West Elk Mine <br />• Surface Water Oua[ity Elfects <br />Potential effects on surface water quality from mining (relative to the overall mine) could occur <br />from: (1) runoff from disturbed azeas, (2) seepage from waste rock or coal refused piles to the <br />stream/aquifer system, (3) dischazge of mine water, (4) dischazge of sanitary wastewater, and (5) <br />subsidence-related factors. For the Apache Rocks and Box Canyon permit revision areas <br />specifically, factors (3), (4), and (5) apply. For the South of Divide permit revision azea <br />specifically, factors (1), (3), and (5) apply. <br />Runoff from Disturbed Areas <br />Runoff due to rainfall or snowmelt from disturbed azeas would have a higher amount of <br />suspended solids and associated pollutants than undisturbed areas. However, it is required that <br />runoff from all disturbed areas be detained in sediment control ponds or a similar system, and the <br />dischazges from the ponds comply with NPDES effluent limitations. In addition, disturbed azeas <br />are re-vegetated, which reduces sediment levels. <br />Runoff from mine site azeas is collected and treated in sediment ponds, except for a few areas <br />designated as Small Area Exemptions (see Exhibit 66). Data from these dischazges is included <br />in the MCC Quarterly Hydrology Reports (1982 to 1987) and in the Annual Hydrology Reports <br />(1982 to present). Dischazges have complied with NPDES/CDPS permit requirements with only <br />a few minor exceptions. No significant impacts to the North Fork from sediment pond <br />discharges have been observed or aze indicated by sample results. <br />Table 50 summazizes quarterly NPDES water quality from sediment pond MB-2R from October <br />1993 through September 1994, and aze indicative of the mine site pond water. It is appazent <br />from the previous quarterly monitoring reports and Table 50 that sediment pond discharges have <br />no adverse effect on the North Fork or water quality standards. The quality of pond dischazge <br />often exceeds the quality of the North Fork and so provides dilution. The discharge flows aze <br />small relative to the North Fork flow, so that incremental changes in concentrations aze <br />imperceptible. <br />All dischazges aze treated to meet effluent limits. Comparison of Table 50 values to effluent <br />limits in Table 51 shows that the pond dischazges typically meet the effluent limits for the pond. <br />Sedimentation in the ponds reduces levels of total suspended solids (TSS), and the pH typically <br />decreases as pond water equilibrates with the atmosphere. Total iron, pH, and TDS in discharges <br />resulting from future mining should be similar to the values reported in Table 50. <br />Table 50 <br />Summa of Dischar a Water Quali From Sediment Pond MB-2R Water Year 1994 <br />Parameter No. of Sam les Mean Minimum Maximum <br />H S.U. 19 8.1 7.4 8.6 <br />TDS m 19 596 349 1190 <br />TSS m 2 19 12.6 0.9 47 <br />Total Iron m 2 19 0.26 L.D. 1.22 <br /> <br />1.05-118 Revised November 1004 PR70; Rev. March 1006; Rev. May 1006 PRIG <br />