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contained within the CHIS for the North Fork Gunnison River. The PHC separately <br />addresses potential effects on groundwater and surface water. <br />Effects on Groundwater <br />Mining of the Elk Creek Mine will have some impact the groundwater regime within <br />the immediate azea of the proposed operation, but, as with the Somerset and <br />Sanborn Creek Mines, the impact will not cause material damage to the ground <br />water regime. <br />Though the Sanborn Creek operation mined both the B and C seams that had been <br />mined before at the old Somerset Mine, the Sanborn Creek Mine was not connected <br />to the old workings and was protected by a 100-foot buffer. The old Somerset mine <br />is thought to be flooded and that buffer was appazently successful in protecting the <br />newer operation from inundation from the old workings. The 100-foot buffer was <br />maintained by advance drilling to fmd the location of the old workings. <br />Mine water inflow into the Sanborn Creek workings is estimated to be 425 gpm or <br />less. The old Somerset Mine had an inflow rate of 0.15667 gpm/acre for the 1,500 <br />acres of development in the mine that was below the level of the North Fork River. <br />Projecting this rate to the 2,600 acres of the Sanborn Tracts yields an inflow of 407 <br />gpm. The operator has rounded this figure to 425 gpm in the pemut document. It is <br />not known at the time of this fmdings document what the source of the mine inflow <br />water was during the spontaneous combustion problem in 1999. The operator has <br />also projected an additiona1235 gpm dischazge from the old Somerset Mine, which <br />might reach the North Fork via the alluvial system. This is considered to be <br />extremely unlikely; however, the projection is used in the CHIS to allow for absolute <br />worst-case prediction. The following are potential sources for inflow: <br />The North Fork of the Gunnison River is 750 feet to the south and 100 feet <br />above the proposed B-seam workings and 40 feet above the C-seam workings. <br />Groundwater is expected to travel downdip from the river through the coal and <br />overburden into the mine workings. Because of the low permeability of the <br />coal and overburden, calculations have shown that these flows should be minor. <br />The flows can be expected to occur with a considerable lag time. There will be <br />a compazable diminution of flow in the North Fork but mine pumpage will <br />return this amount to the river, minus that used in the mine. The cone of <br />depression from dewatering of the strata will only extend to the boundary of the <br />North Fork and will not adversely impact any wells. <br />2. The potential exists that the mine may encounter water inflow from faults and <br />fractures. No particular faults have been identified. The lazgest fault that the <br />old Somerset Mine encountered had a sustained inflow of 120 gpm, which <br />contributed 50 percent of the total inflow. <br />21 <br />