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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 />3.3. Subsidence Prediction <br />Ten panels in the Wadge Seam have previously undermined the Energy Spur in the Northern Mining <br />District. Subsidence data, obtained from surveys of ground stations conducted during these periods <br />of undermining, were previously used to check the initial predictions and this will again be done during <br />undermining by the Wolf Creek Seam panels. <br />Table 1 and Figure 6 shows the predicted subsidence profile along the Energy Spur due to <br />sequentially mining all seven panels without remediation. Maximum subsidence effects without <br />remediation are estimated at: <br />1. Maximum subsidence of 74- inches where the track runs over the shallower panels. <br />2. Maximum slope change of 1.0 %. <br />These predicted impacts will require remedial actions to maintain the track within the gradient <br />tolerances required by the railroad. <br />3.4. Candidate 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 partially <br />compensate for the subsidence that will occur. Pre - ballasting further involves the pre - placement of <br />ballast in advance of mining, while "partial re- leveling during track undermining" involves sequential <br />placement of ballast and track tamping, on a daily basis, during track undermining. <br />Both of these methods have been successfully used during the prior phases of track undermining <br />3.4.1. Remedial Planning <br />Three steps are typically involved in remedial planning. The first step is to model the predicted <br />subsided elevation for each railroad Station for the longwall panel being extracted. The second step is <br />to survey the section of track that will be subject to subsidence, and the third step involves modelling <br />the required track re- elevation necessary to ensure that differential gradient tolerances can be <br />maintained in the future. <br />Field implementation of the re- elevation (or re- leveling) program will require either (1) pre - ballasting <br />of the Energy Spur in advance of undermining followed by periodic survey of the alignment during <br />undermining, or (2) re- leveling the Energy Spur during undermining. Additional detailed remedial <br />planning work will be carried out prior to each panel undermining the track. Tasks will include: <br />1. Quantifying ballast requirements. The amount of material required for re- leveling will be <br />estimated from the existing ballast cross - sections and predicted subsidence. <br />2. Making drainage provisions. Surface water drains alongside each side of the track to culverts <br />placed at strategic locations. These culverts must be lengthened during track re- ballasting, <br />the additional length being determined based on the required increase in ballast height. <br />7 P N : 2013 -26 <br />