Laserfiche WebLink
SubTerra, Inc. Peabody Twentymile Coal LLC 09/27/2014 <br />Foidel Creek Mine <br />Permit Revision for Longwall Mining in the Wolf Creek Seam - Subsidence Evaluation <br />5.3.2. 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 9- <br />Right is 1,800 -feet providing for a panel width /panel depth ratio of 0.55 and a maximum predicted <br />subsidence of 45- inches at the center of the panel. Figure 5 shows the fully developed transverse <br />profile for the 9 -Right longwall looking westward in the direction of face retreat. 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 left side of the figure represents the "hump" that will develop over the pillars separating 8 -Right <br />and 9- Right. Each pylon on the Archer - Hayden line (Drawing 13) is located approximately 100 -feet <br />from the center of 9 -Right and is predicted to subside by about 3 -ft as shown in Table 5. Each pylon <br />on the Craig- Hayden - Steamboat line (Drawing 14) is located approximately 250 -feet from the center <br />of 9 -Right and is predicted to subside by about 2 -ft as shown in Table 6. <br />The fully developed profile shown on Figure 5 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 9. <br />5.4. Power Line Subsidence <br />5.4.1. Clearance Issues <br />5.4.1.1. Foidel Creek - Steamboat Transmission Line <br />As shown on Drawing 15, 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 parcels is minimal. Possible clearance losses as <br />the line crosses the recovery room at 1 -Right and the start room at 5 -Right are estimated at 1 to 2 -ft <br />due to the gradual change in subsidence at adjacent structures (see Table 4). <br />5.4.1.2. 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 145 will not subside and Pylon 146 is predicted to <br />subside by about 2.8 -feet. At the eastern end, Pylon 152 will not subside, Pylon 151 is predicted to <br />subside by about 3.3 -feet. <br />At the western end of the Craig - Hayden- Steamboat line, Pylon 146 -4 will not subside and Pylon 146 -3 <br />is predicted to subside by 2 -feet. At the eastern end, Pylon 145 -1 will not subside and Pylon 145 -2 is <br />predicted to subside by about 2 -feet. <br />The net effect on power line clearance will be a decrease of about 1 -feet at either end of Panel 9- <br />Right. <br />13 PN: 2013 -26 <br />