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Subsidence Evaluation for the <br />Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 28 <br /> <br />831-032.923 Wright Water Engineers, Inc. <br />December 2021 <br />9.0 WATER AND METHANE <br />Observations of the north and west flanks of Mt. Gunnison during aerial geologic mapping and an <br />October 1996 field trip revealed numerous talus and rock glacier deposits that occur in the valleys <br />and lower part of this intrusive body. Snowmelt and rain can easily infiltrate these deposits, which <br />may eventually enter any permeable rocks, faults, fractures, and joints near the mountain. Coal <br />beds and rocks in the deformed zone around Mt. Gunnison may also contain increased <br />concentrations of methane where the coal is deformed and perhaps metamorphosed to a higher <br />rank by the intrusive body. Greater quantities of water and methane may therefore be expected as <br />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 the <br />amount of subsidence that can be expected. In the Southern Panels, Apache Rocks West, and <br />Sunset Trail mining areas where water might be encountered in an area equal to, or greater than, <br />the width of the proposed longwall panels, maximum vertical displacement may be expected to <br />approach 0.8t.