2019-12-31_REVISION - C1981022 (15)

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found on Page 2.05-96b of the PAP. A similar mine water transfer operation was proposed for the Hubbard Creek Fan-site facility, and approved under TR-51 in September 2005. With this operation, D-Seam water may be transferred to the B-Seam workings. 2. 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 on pages 2.05-34 through 38 and Map 2.05-M4 (sheets 1 through 6) of the PAP. 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. The operator was permitted use about 36.4 acre-feet per year for underground and above-ground dust suppression at the production rate of 6 million tons/year. The water was drawn from an existing surface water right of 1,300 acre-feet per year on the North Fork of the Gunnison River. More detailed information is available in the CHIA for the North Fork of the Gunnison River. 22