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for the reestablishment of appropriate riparian vegetation. <br />K. Probable Hydrologic Consequences of Mining (2.05.6(3)(b)(iii)) <br />This section reviews the Probable Hydrologic Consequences (PHC) of mining at the <br />Somerset Mine, Sanborn Creek, and Elk Creek Mine locations. The review includes <br />the probable consequences which will result from the three mines. The Cumulative <br />Hydrologic Impact Study (CHIS) for the North Fork of the Gunnison River contains <br />a detailed analysis of the cumulative impacts of all currently permitted mine <br />activities within the North Fork of the Gunnison River drainage basin. The CHIS <br />document is available for review at the Division office. This PHC is based upon <br />information contained within Permit No. C -81 -022 (Somerset Mine, Sanborn Creek <br />Mine, and Elk Creek Mine) and upon the analyses contained within the CHIS for the <br />North Fork Gunnison River. The PHC separately addresses potential effects on <br />groundwater and surface water. <br />Effects on Groundwater <br />Mining of the Elk Creek Mine will have some impact the groundwater regime <br />within the immediate area 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 apparently successful in protecting the <br />newer operation from inundation from the old workings. The 100 -foot buffer was <br />maintained by advance drilling to find 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 permit document. It is <br />not known at the time of this findings 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 additional 235 gpm discharge 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 <br />absolute 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 down dip from the river through the coal and <br />overburden into the mine workings. Because of the low permeability of the <br />21 <br />