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SubTerra, Inc. Twentymile Coal Company 6/19/2003 <br />19-Right Power Line Study <br />at depths from 600-ft to over 1,000-ft. These data were used to create Figure 2, which shows the <br />relationship between maximum subsidence and the panel width/panel depth ratio. <br />Cover in the Northern Mining District is typically thicker than elsewhere in the mine and ranges <br />from 1,100 to 1,400-ft providing for panel width/panel depth ratios of from 0.9 to 0.7. Figures 3 <br />and 4 show transverse subsidence profile predictions for this range in conditions. These are the <br />predicted final profiles that would be realized after a panel has passed at least full depth past the <br />point of the section. Figure 5 shows the fully developed transverse profile for the 19-Right <br />longwall looking westward in the direction of face retreat. The left side of the figure thus <br />represents the "hump" that will develop over the pillars separating 18 and 19-Right. Each pylon <br />on the Archer-Hayden line is located approximately 250-ft from the center of 19-Right towards 18- <br />Right (to the left on Figure 5). Each pylon on the Craig-Hayden-Steamboat line is located <br />approximately 400-ft from the center of 19-Right towards 18-Right (again, to the left on Figure 5). <br />The fully developed profile shown in the preceding figures will take from 20 to 25-days to develop <br />depending on the rates of face retreat. Each structure will start to subside when the panel is 400- <br />ftfrom the structure. Subsidence will be, for the most part, complete once the panel has passed <br />about 600-ft past each structure. This transitional movement is represented by the traveling <br />subsidence profile shown in Figure 6. <br />Each end of the line will be affected by either the start or recovery room profile (Figure 7). <br />Structure 145-1 on the Archer-Hayden line is located approximately 300-ft in front of Panel 19- <br />Right's Start room and will therefore be subject to about 65% of maximum subsidence, or about <br />30-inches. Structure 152 on the Craig-Steamboat line is located about 400-ft from the Start Room <br />• and is predicted to subside by about 22-inches. <br />3. Power Line Subsidence <br />3.1 Clearance Issues <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. <br />Two exceptions to this general rule will occur at each end of the longwall. At the western end of <br />the Archer-Hayden line, Pylon 147-4 will not subside and Pylon 147-3 is predicted to subside by <br />about 4-ft. At the eastern end, Pylon 144-6 will not subside, Pylon 145-1 is predicted to subside <br />by about 30-inches and Pylon 145-2 is predicted to subside by about 4-ft. <br />At the western end of the Craig-Hayden-Steamboat line, Pylon 141 will not subside and Pylon 142 <br />is predicted to subside by just over 30-inches. At the eastern end, Pylon 153 will not subside, <br />Pylon 152 is predicted to subside by about 22-inches, and Pylon 151 is predicted to subside by <br />about 30-inches. <br />The existing clearance profiles for both lines are shown, for reference purposes, in Figures 8 and <br />9, and Tables 1 and 2. Clearance profiles for the eastern end of the longwall are shown on <br />Figures 8(a) and 9(a) and for the western end on Figures 8(b) and 9(b). <br />3.2 Structure Tilt <br />Each structure will start to subside when the longwall face retreats to within 400-ft of its <br />foundation. At this time, the structure will begin to tilt backwards towards the approaching face <br />and inwards towards the center of the panel. As the face passes by, the structure will tilt back to <br />