2000-09-25_GENERAL DOCUMENTS - C1981022

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Projecting this rate [o the 2,600 acres of the Sanbom Tracts yields an inflow of 407 gpm. The operator has rounded this figure to 425 gpm in the permit document. It is not known at the time of this findings document what the source of the mine inflow water was during the spontaneous combustion problem in 1999. The operator has also projected an additional 235 gpm discharge from the old Somerset Mine, which might reach the North Fork via the alluvial system. This is considered to be extremely unlikely; however, the projection is used in the CHIS to allow for absolute worst-case prediction. The following are potential sources for inflow: 1. The North Fork of the Gunnison River is 750 feet to the south and l00 feet above the proposed B-seam workings and 40 feet above the C-seam workings. Groundwater is expected to travel downdip from the river through the coal and overburden into the mine workings. Because of the low permeability of the coal and overburden, calculations have shown that these flows should be minor. The flows can be expected to occur with a considerable lag time. There will be a comparable diminution of flow in the North Fork but mine pumpage will return this amount to the river, minus that used in the mine. The cone of depression from dewatering of the strata will only extend to the boundary of the North Fork and will not adversely impact any wells. 2. There is the potential that the mine may encounter water inflow from faults and fractures. The location of these faults is unknown. The largest fault that the old Somerset Mine encountered had a sustained inflow of 120 gpm, which contributed 50 percent of [he total inflow. The Somerset Mine has committed to conducting a study of the potential for mine inflow from the faults and fractures in the Coal Gulch area. 3. The Sanborn Creek workings will undermine portions of two abandoned mines - the Oliver Mine and the Hawk's Nest Mine. The Oliver Mine was mined in the I930's and is known to be completely flooded. An exposure of the workings adjacent to the old county road is discharging water at a rate of a few gallons per minute. About 90 percent of the workings of this mine lie downdip of the discharge point. The Hawk's Nest Mine lies north of the Oliver Mine and is stratigraphically higher than the Oliver D seam. Hawk's Nest mined in both the E and F seams. The workings of this mine are probably not flooded, as indicated by measurements in an old drill hole. Also, daring operation of the Hawk's Nest Mine, there was very little inflow. Because there is the potential that subsidence could cause fracturing of the interburden between the B seam and the flooded workings of the Oliver Mine, Oxbow Mining, Inc. has committed to limited extraction in the Sanbom Creek Tracts under those areas known to be flooded. This would avoid catastrophic 20