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West Elk Mine <br />L.. <br />extremely unlikely that they extend downward to the B-Seam through multiple shale and siltstone <br />units, Using this conservative evaluation, it is now important to evaluate the potential impact that <br />subsidence may have on any pre-mining fractures. <br />Evaluation of subsidence due to downwarping oflaterally-constrained strata shows that rock strata <br />with different deformation and strength characteristics deform as discrete units. For example, <br />strata of shale and siltsone behave as units discrete from sandstone. Above the fractured zone and <br />within the continuous deformation zone these units undergo continuous flexure (Figure 1, <br />enlargement 2 of Exhibit 60). Above the neutral surfaces, in zones of convex-upward curvature, <br />the material is in tension and below them, the material is in compression. <br />Consequently, stresses change across neutral surfaces from tension to compression with each <br />successive rock unit that deforms as a plate. Fractures aheady present would thus tend to open <br />more in the zones of tension and close more in the zones of compression than would be the case <br />for these fractures prior to mining and subsidence. The Box Canyon and unnamed drainage west <br />of Box Canyon channels are above the maximum estimated height of the fracture zone (i.e., 20t <br />or 240 feet fora 12-foot coal-extraction thickness). <br />After longwall mining is completed in the area and static conditions are attained, the zones of <br />tension and compression commonly cease, and any fractures present will likely resume the pre- <br />mising condition. Therefore, the impacts on surface flow in the drainage of the Box Canyon <br />permit revision azea aze likely to be minimal or non-existent under even the most conservative <br />assumptions. <br />Water and Methane <br />Observations of the north and west flanks of Mt. Gunnison during an October 1996 field trip, <br />revealed numerous talus and rock glacier deposits that occur in the valleys and lower part of this <br />intrusive body. Snow melt and rain can easily infiltrate these deposits, which may eventually <br />enter any permeable rocks, faults, fractures, and joints near the mountain. Coal beds and rocks in <br />the deformed zone around Mt. Gunnison might also contain increased methane where the coal is <br />metamorphosed to a higher rank by the intrusive body. Great quantities of water and methane <br />may therefore be expected as coal is mined closer to Mt. Gunnison. <br />Water and Methane in the Oliver No. 2 Mine <br />Because lazge quantities of water and methane were encountered while mining the E/DO-Seam in <br />the Oliver No. 2 Mine, other sources may also be present in the Box Canyon ruining area. In the <br />report on the closure of the Oliver No. 2 Mine, lazge volumes of water and methane began to <br />flow from fractures in the floor of the southernmost (top) entry of 6'" East. The mine was <br />evacuated and closed because the water and methane flowed in quantities too costly to control. <br />This area where the large outpouring of water and methane occurred is located about 300 feet <br />south of entries of the South Mains that were not driven further, apparently because of roof <br />.~ control problems. <br />2.05-127 Revised Jun. J995 PR06: 1/96 RN03; RevisedJan. 7998 PR08 <br />