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C~ <br />• <br />Mountain Coa! Compnm~ 2000 Annual Hydrology Report <br />Assessment of Mining Impacts to Hydrologic Resources <br />West Elk A9ine <br />Surface Water Impacts <br />While MCC maintains a comprehensive network of streamflow gaging stations throughout the <br />permit and lease areas, few of the monitored streams have been directly within the influence of <br />mining (Map 2) to date. In July ]998, longwall mining progressed into the Minnesota Creek <br />drainage. Flow tables and hydrographs for the surface water stations with continuous recorders <br />are contained in Appendices A and B, respectively. Water quality and field parameters for all <br />surface water stations are located in Appendix C. These data indicate that there have been no <br />impacts to surface waters due to mining. <br />Impact of TDS on the North Fork <br />WWE evaluated the concentrations of the individual parameters that collectively constitute the <br />TDS in mine discharges, and determined that the pond discharge water is predominantly sodium <br />carbonate/sodium bicarbonate in nature. Aside from high concentrations of sodium, none of the <br />other parameters, including heavy metals, are found in significant concentrations. There are no <br />applicable numeric standards or criteria for sodium. <br />WWE has reviewed the salinity (TDS) loading analysis in the most recent version of the North <br />Fork Cumulative Hydrologic Impacts Analvsis (CHIA), in the context of MCC's WY00 <br />discharges. In the 1997 CH1A, CDMG calculated the cumulative TDS (salinity) loading to the <br />North Fork from coal mines located in the North Fork valley. The assumptions used for MCC's <br />contribution were a discharge rate of 1,000 gpm (2.23 cfs) and a TDS concentration of 2,500 <br />mg/L. When assessing WY00, the total volume discharged from ponds MB-l, MB-2R, MB-3, <br />MB-5, SG~ 1, ?iPE, ~11'~'PF and Lone Pine pipeline was approximately 659 acre-feet, which <br />translates to an average continuous discharge rate of approximately 409 gpm (0.91 cfs). Based <br />on the 2000 Discharge Monitoring Reports for the ponds, the flow-weighted, maximum TDS <br />concentrations were as follows: MB-] = 745 mg/L; MB-2R = 540 mg/L; MB-4 = 354 mg/L; SG- <br />1 = 590 mg/L; RPE = 796 mg/L; MWPF = 4067 mg/L; and Lone Pine pipeline = 2715 mg/L. <br />Consequently, the annual salinity loading to the North Fork from the West Elk Mine for WY00 <br />was 2,670 tons, which is well below the value assumed in the CHIA as shown in Table 10. <br />Table 10 <br />W1'00 Salinity Loading Relative to 1997 CHIA Analysis <br /> <br /> Avg. Continuous TDS Annual Salt <br /> Discharge Rate Concentration Loading Percent of CHIA <br />Scenario (gpm) (mg/L) (tons/year) Loading <br />WY00 409 2,760 2,670 48 percent <br />1997 CHIA 1,000 2,500 5,670 -- <br />83/-03?.550 Page 23 Wright LVnrerEngineers <br />