2009-02-09_GENERAL DOCUMENTS - C1981022 (3)

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C-1981-022 RN-05 Findings February 2009 inflows of approximately 10 gpm. These inflow totals led to the conclusion that there is little likelihood of eventual discharge from the portals. In October 2004, the Division approved TR-47, which proposed to transfer mine sump water from the D-Seam to the underlying abandoned C seam workings at a rate of up to 3 million gallons per year via a surface borehole located in the upper Elk Creek facilities. A description of the operation is found on Page 2.05-96b. A similar mine water transfer operation was proposed for the Hubbard Creek Fansite facility, and approved under TR-51 in September 2005. With this operation, D-Seam water may be transferred to the B-Seam workings. Effects on Surface Water The areas of surface disturbance at the Somerset Mine are protected by sediment control systems including diversion and containment ditches, sediment ponds, and other alternate sediment control features such as rock, vegetation and straw filters. All point source discharges are regulated under the National Pollution Discharge Elimination System (NPDES). Specific details regarding the sediment and drainage control systems are found in the Sanborn Creek Mine Permit, pages 2.05-34 through 38 and Map 2.05- M4 (sheets 1 through 6). Drainage from disturbed areas can contribute additional suspended solids to offsite stream systems; however, the above-referenced sediment control systems will effectively control sediment yield to offsite areas. Other applicable effluent limitations will also be met, as required by the NPDES permit. There is no evidence of acid-forming or toxic-producing materials. The operation will result in slightly increased total dissolved solids levels in the North Fork of the Gunnison River. The sources are the discharge from the underground workings of the Elk Creek Tract, and drainage from waste piles located at the site. The previously documented discharges from the Somerset Mine no longer exist since mining and mine dewatering activities have ceased and the old portals have been permanently sealed. Specific anticipated water quality impacts are discussed within the Cumulative Hydrologic Impact Study for the North Fork of the Gunnison River. It has been found that the Elk Creek Mine operation will not cause significant salinity increase in the North Fork of the Gunnison River. The mine will not adversely impact flooding processes or streamflows in the North Fork of the Gunnison River. Mining operations are not expected to decrease flows in any of the ephemeral or intermittent drainages to be undermined. The operation will not adversely impact downstream water users. 25