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Mine water inflow into the Sanborn Creek workings is estimated to be 425 <br />gpm or less. The old Somerset Mine had an inflow rate of 0.15667 gpm /acre <br />for the 1,500 acres of development in the mine that was below the level of the <br />North Fork River. Projecting this rate to the 2,600 acres of the Sanborn Tracts <br />yields an inflow of 407 gpm. The operator has rounded this figure to 425 gpm <br />in the permit document. It is not known at the time of this findings document <br />what the source of the mine inflow water was during the spontaneous <br />combustion problem in 1999. The operator has also projected an additional <br />235 gpm discharge from the old Somerset Mine, which might reach the North <br />Fork via the alluvial system. This is considered to be extremely unlikely; <br />however, the projection is used in the CHIS to allow for absolute worst -case <br />prediction. The following are potential sources for inflow: <br />(a) 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 <br />workings. Groundwater is expected to travel down dip from the river <br />through the coal and overburden into the mine workings. Because of the <br />low permeability of the coal and overburden, calculations have shown that <br />these flows should be minor. The flows can be expected to occur with a <br />considerable lag time. There will be a comparable diminution of flow in <br />the North Fork but mine pumpage will return this amount to the river, <br />minus that used in the mine. The cone of depression from dewatering of <br />the strata will only extend to the boundary of the North Fork and will not <br />adversely impact any wells. <br />(b) The potential exists that the mine may encounter water inflow from faults <br />and fractures. No particular faults have been identified. The largest fault <br />that the old Somerset Mine encountered had a sustained inflow of 120 <br />gpm, which contributed 50 percent of the total inflow. <br />(c) The Sanborn Creek workings undermined portions of two abandoned <br />mines - the Oliver Mine and the Hawk's Nest Mine. The Oliver Mine was <br />mined in the 1930's and is thought to be flooded. An exposure of the <br />workings adjacent to the old county road formerly discharged water at a <br />rate of a few gallons per minute. About 90 percent of the workings of this <br />mine lie downdip of the discharge point. <br />The Hawk's Nest Mine lies north of the Oliver Mine and is <br />stratigraphically higher than the Oliver D seam. Hawk's Nest mined in <br />both the E and F seams. The workings of this mine are probably not <br />flooded, as indicated by measurements in an old drill hole. Also, during <br />operation of the Hawk's Nest Mine, there was very little inflow. <br />Because potential exists for subsidence to cause fracturing of the <br />interburden between the B seam and the flooded workings of the Oliver <br />Mine, Oxbow Mining, LLC limited extraction in the Sanborn Creek Tracts <br />21 <br />