REP32708 - Laserfiche WebLink

Home Browse Search

Draft West Elk Mine 2005 Annual Hydrology Report 36 I ~ 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 Mazch 2001. Based on the water quality and flow monitoring data from WY 2005 (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 2005 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 WY 2005 as well as in previous years (WY 2001 - 2004), the flow data from the Upper and Lower Deep Creek (Appendix A) stations are suspect, due to the lack of flumes and channel variations. 5.1.2 Impacts to the North Fork of the Gunnison River MCC discharges water (Figure 8) to the North Fork 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 dischazge water are sodium and bicazbonate. The sediment pond discharge waters are slightly alkaline with pH ranging from 6.52 to 8.72, with average TDS concentration ranging from 300 mg/1 to 3,500 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 alkaline with pH values ranging from 8.07 to 8.44 and average TDS concentrations ranging from about 2,942 to 3,145 mg/1. A salinity (TDS) loading analysis of the MCC's WY 2005 discharges was completed relative to the current North Fork Cumulative Hydrologic Impacts Analysis (CHIS) (CDMG, 2003). The CHIS analysis was conducted to assess the potential cumulative hydrologic impacts of mining and other activities in the North Fork Valley on the North Fork's water quality and flow. The CHIS analysis determined that no significant hydrologic impacts were expected as a result of mining activities. The CHIS assumed that MCC's contribution to the North Fork would be a maximum of 5,520 gpm with a TDS concentration of 2,500 mg/1. The total WY 2005 discharge from the Project as reported from the CDPS reports was approximately 330 gpm (Table 9), Based on this value the flow-weighted maximum annual salinity (TDS) load from the Prolect was 2107 tons This • represents about 6.8 percent of the value used in the CHIS Tlie overall.gisperal wate.l~lance:£or fheeJ?roJeet as presented tn_~igure3 was=estmated Lobe ai~ou(.= gpm.whlchas oii`ljl, ,}~peccetit September 2006 HydroGeo, Inc.