2008-06-27_REPORT - C1980007 (4)

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West Elk Mine 2007 Annual Hydrology Report 41 • 5.0 ASSESSMENT OF MINE-INDUCED HYDROLOGIC IMPACTS AND ANTICIPATED IMPACTS IN WY 2007 5.1 Surface Water MCC maintains a network of 23 stream flow gauging stations throughout the permit and lease areas (Table 2). The locations of the surface water monitoring stations are shown on Map 2. Daily mean flow summary tables are presented in Appendix A. Surface water flow hydrographs are presented in Appendix B and the field and laboratory surface water quality data are presented in Appendix C. 5.1.1 Impacts to Area Stream Water Quantity and Quality The West Elk mining activity has approached only two perennial streams in the Project area, Minnesota Creek and Deep Creek. Long wall mining operations in the Minnesota Creek drainage area took place from July 1998 to February 2001. Longwall mining in the Deep Creek drainage began in March 2001. Based on the water quality and flow monitoring data from WY 2007 (see • Appendices A, B, and C), there have been no apparent mining-induced impacts to the water quality or quantity of these streams with the exception of Sylvester Gulch. The water sampled at the Middle and Lower Sylvester Gulch monitoring stations in WY 2007 consisted almost entirely of the permitted mine water releases. Therefore the analyses at these locations show considerable mining related increases in constituent levels and flows when compared with baseline data. It is important to note that in previous years (WY 2001 - WY 2006) the flow data from the Upper and Lower Deep Creek (Appendix A) stations have been designated as suspect, due to the lack of flumes and channel variations. Current monitoring (including WY 2007) protocols stipulate the collection of instantaneous flow measurements three times per year. 5.1.2 Impacts to the North Fork of the Gunnison River MCC discharges water (Figure 8) to the North Fork of the Gunnison River via sedimentation ponds (MB-2R and MB-4) and direct discharges to Sylvester Gulch (discharge points 017A and 018a). The major cations and anions of the sedimentation pond discharge water are sodium and bicarbonate. The sediment pond discharge waters ranged from slightly acidic to slightly alkaline with pH values ranging from 6.58 to 8.98 and with average TDS concentration ranging from 129 . mg/l to 12,950 mg/1. The major cations and anions of the Sylvester Gulch discharge water are also sodium and bicarbonate. The Sylvester Gulch discharge water is slightly to moderately alkaline June 2008 HydroGeo, Inc.