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SubTerra, Inc. Twentymile Coal Company 6119/2003 <br />PR6 Rail Line Evaluation <br />• process was repeated for panels 15 through 18-Right and the results incorporated in the remedial <br />action simulations presented below. <br />3. Remedial Actions <br />Two potential remedial schemes are associated with this study, partial re-leveling with pre- <br />ballasting of the track, and partial re-leveling during track undermining. Both partial re-leveling <br />schemes involve calculating the amounts of ballast required at each Station to partialy <br />compensate for the subsidence that will occur. Pre-ballasting further involves the pre- <br />placement of ballast in advance of mining, while "partial re-leveling during track undermining" <br />involves sequential placement of ballast and track tamping, on a daily basis, during track <br />undermining. <br />Both of these methods have been successfully used during the prior phases of track <br />undermining. <br />3.1 Remedial Planning <br />There were two steps involved in remedial planning. The first step was to model the predicted <br />subsided elevation for each railroad Station (e.g., see Table 1, Column 4 and Figure 7). The third <br />step was to model the required track re-elevation required to ensure that differential gradient <br />tolerances can be maintained in the future (e.g., see Table 1, Column 9 and Figures 7 and 8). <br />• Figures 6 and 7 present the cumulative subsidence and required re-elevation curves for 14 Right. <br />Each of the subsequent extractions has been modeled to produce the following results: <br />1. Table 2 and Figures 8 and 9 show the predicted subsidence and estimated re-elevation <br />requirements associated with the extraction of 15-Right. <br />2. Table 3 and Figures 10 and 11 show the predicted subsidence and estimated re-elevation <br />requirements associated with the extraction of 16-Right. <br />3. Table 4 and Figures 13 and 14 show the predicted subsidence and estimated re-elevation <br />requirements associated with the extraction of 17-Right. <br />4. Table 5 and Figures 16 and 17 show the predicted subsidence and estimated re-elevation <br />requirements associated with the extraction of 18-Right. <br />3.2 Effect of Planned Remediation on Fish Creek and Its AVF <br />As shown on Figure 1, the first area where remedial re-ballasting may impact Fish Creek or its <br />AVF is where the track crosses 16-Right. Figure 12 shows the plan and cross-section for the <br />track at this location (approximately at Station 416). The predicted magnitude of required re- <br />elevation at this Station is shown in Table 3, Column 9 as approximately 3-ft. This will require <br />extending the base of the ballast prism by 6-ft (at 2:1, H:V) on either side of the track which should <br />not be a problem at this location. <br />The second area of potential concern is where the track crosses over Fish Creek, approximately <br />at Station 401. Figure 15 shows the plan and cross-section for the track at this location. The <br />• predicted magnitude of required re-elevation at this Station is shown in Table 4, Column 9 as <br />approximately 3-ft. This will again require extending the base of the ballast prism by 6-ft (at 2:1, <br />3 <br />