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SubTerra, Inc. Peabody Twentymile Coal, LLC 03/16/2015 <br />Foidel Creek Mine <br />Permit Revision for Longwall Mining in the Wolf Creek Seam - Subsidence Evaluation <br />6.3.2. Archer -Hayden and Craig -Hayden -Steamboat Transmission Lines <br />Cover in the Northern Mining District is typically thicker than elsewhere in the mine and along Panel <br />12 -East is 1,600 -feet providing for a panel width/panel depth ratio of 0.63 and a maximum predicted <br />subsidence of 57 -inches at the center of the panel. Figure 4 shows the fully developed transverse <br />profile for the 12 -East longwall looking eastward towards 12 -East's start room. This is the predicted <br />final profile that would be realized after a panel has passed at least full depth past the point of the <br />section. <br />The center of the figure represents the "hump" that will develop over the pillars separating 12 -East and <br />11 -East. Each pylon on the Archer -Hayden line (Drawing 14) is located approximately near the center <br />of 9 -East and is predicted to subside by about 56 -in as shown in Table 7. Each pylon on the Craig - <br />Hayden -Steamboat line (Drawing 15) is located approximately 150 -feet from the center of 12 -East and <br />is predicted to subside by about 4 -ft as shown in Table 8. <br />The fully developed profile shown on Figure 4 will take from 25 to 35 -days to develop depending on <br />the rates of face retreat. Each structure will start to subside when the panel is 500 -feet from the <br />structure and subsidence will be, for the most part, complete once the panel has passed about 1,000 - <br />feet past each structure. This transitional movement is represented by the traveling subsidence profile <br />shown in Figure 10. <br />6.4. Power Line Subsidence <br />6.4.1. Clearance Issues <br />6.4.1.1. Foidel Creek -Steamboat Transmission Line <br />As shown on Drawing 16, the Foidel Creek -Steamboat Transmission Line has Structures located <br />over or in close proximity to the pillars separating each panel so that the potential for a loss of <br />clearance as the Transmission Line runs between panels is minimal. Possible clearance losses as <br />the line crosses the recovery room at 5 -East and the start room at 7 -East are estimated at 1 to 2 -ft <br />due to the gradual change in subsidence at adjacent structures (see Table 6). <br />6.4.1.2. Archer -Hayden and Craig -Hayden -Steamboat Transmission Lines <br />Clearance changes are unlikely to be a problem as each of the power poles is located equidistant <br />from the panel center and will thus experience about the same amount of vertical subsidence. Two <br />exceptions to this general rule will occur at each end of the longwall. <br />At the western end of the Archer -Hayden line, Pylon 143 will not subside and Pylon 144 is predicted to <br />subside by about 3.2 -feet. At the eastern end, Pylon 152 will not subside and Pylon 151 is predicted <br />to subside by about 4.5 -feet. <br />At the western end of the Craig -Hayden -Steamboat line, Pylon 146-6 will not subside and Pylon 146-5 <br />is predicted to subside by 3.7 -feet. At the eastern end, Pylon 145-1 will not subside and Pylon 145-2 <br />is predicted to subside by about 4 -feet. <br />The net effect on power line clearance will be a decrease of about 1 -feet at either end of Panel 9 -East <br />14 PN: 2013-26 <br />