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Subsidence Evaluation for the <br />Exhibit 60E South of Divide and Dry Fork Mining Areas Page 23 <br />9.0 WATER AND METHANE <br />Observations of the north and west flanks of Mt. Gunnison during aerial geologic mapping and <br />an October 1996 field trip revealed numerous talus and rock glacier deposits that occur in the <br />valleys and lower part of this intrusive body. Snowmeh and rain can easily infiltrate these <br />deposits, which may eventually enter any permeable rocks, faults, fractures, and joints near the <br />mountain. Coal beds and rocks in the deformed zone around Mt. Gunnison may also contain <br />increased concentrations of methane where the coal is deformed and perhaps metamorphosed to <br />a higher rank by the intrusive body. Greater quantities of water and methane may therefore be <br />expected as coal is mined closer to Mt. Gunnison. <br />9.1 Potential Impact of Water on Subsidence in Wet Mining Areas <br />As discussed in Section 3.0, the moisture content of the caved and downwarped rocks controls <br />the amount of subsidence that can be expected. In the South of Divide and Dry Fork mining <br />areas where water might be encountered in an area equal to, or greater than, the width of the <br />proposed longwall panels, maximum vertical displacement may be expected to approach 0.8t. <br />17J <br />831 - 032.810 Wright Water Engineers, Inc. <br />