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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 />5. Evaluation of Potential_ Impacts to Powerlines <br />The layout of the Wolf Creek Seam Panels in relation to the Archer - Hayden, Craig- Hayden- <br />Steamboat, and Foidel Creek - Steamboat power transmission lines is shown in Drawings 13, 14 and <br />15. The "H" frame structures of the Foidel Creek - Steamboat line will be sequentially undermined by <br />Panels 5- Right, 4- Right, 3- Right, 2- Right, then 1 -Right over a period of several years. <br />For structures on the parallel Archer- Hayden and Craig - Hayden - Steamboat lines, mining will proceed <br />from the east towards the west in a direction that is almost parallel to the alignment of the power lines, <br />with undermining of the power lines by the last panel (9- Right). The 985 -foot wide Longwall panel will <br />retreat between 40 and 60 -feet per day under normal conditions (subject to market demand), affecting <br />each structure for from 25 to 35 days. <br />5.1. Scope of Work <br />The scope of work covered by this report included predicting transverse and traveling subsidence <br />associated with coal extraction and determining the effects of these predicted movements on the <br />power lines. As noted above, this work followed on from previous work covering subsidence <br />prediction, planning, and observation of power line response when the Archer - Hayden and Craig - <br />Hayden- Steamboat power transmission lines were undermined by Panel 19 -Right in the Wadge <br />Seam. <br />Tasks included: <br />• Digitizing topography along the power line routes (for input to clearance calculations). <br />Twentymile Coal Company supplied the topographic map and aerial photographs for the <br />area. Inputting pylon location coordinates to prediction tables. <br />• Estimating time phased surface and pylon foundation subsidence using the traveling <br />subsidence curve. <br />• Reviewing prior pylon subsidence data (from the eastern mining district) and dummy pylon <br />foundation test (from the southwest mining district) for input to this study. <br />5.2. Approach <br />Our approach included developing a subsidence prediction for mining the Wolf Creek Seam in the <br />Northern Mining district as noted in Section 2. Predicted transverse and traveling subsidence profiles <br />were subsequently used to estimate the time phased movements along those portions of the Foidel <br />Creek- Steamboat lines that cross Panels 1 -Right to 5 -Right and those portions of the Archer- Hayden <br />and Craig - Hayden - Steamboat lines that cross Panel 9- Right. <br />5.3, Subsidence Prediction <br />5.3.1. Foidel Creek - Steamboat Transmission Line <br />Figure 8 shows predicted subsidence along the Foidel Creek - Steamboat line and Table 4 shows the <br />predicted subsidence and permanent tilt at each "H" frame structure. Individual structures will subside <br />by up to 6 -ft with a maximum of 2.5 -in differential settlement between the legs on each structure. <br />12 PN: 2013 -26 <br />