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SubTerra, Inc. Peabody Twentymile Coal, LLC April 11, 2016 <br />Subsidence Mitigation During 9 -East Undermining of the Energy Spur at the Foidel Creek Mine <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 may need to be lengthened during track re - <br />ballasting, the additional length being determined based on the required increase in ballast <br />height. We note that existing survey data indicate that culvert lengths are adequate but it is <br />prudent to confirm this by observation before ballast placement. <br />3. In the case of Option (1), evaluating pre -placement of the Ballast. This involves assessing <br />whether pre -ballasting will result in unacceptable track gradients prior to and during <br />undermining. <br />This process has previously been successfully implemented prior to each panel in the Wadge Seam <br />undermining the Energy Spur. <br />4. Conclusions <br />Some general conclusions that can be drawn from the analysis include: <br />1. The majority of the movement associated with longwall undermining will occur over a one <br />month period starting when the face is about 500 -ft from the rail line and ending when the face <br />is about 500 -ft past the rail line. This distance is measured parallel to face retreat. <br />2. Subsidence at individual Track Station is estimated to be as shown on Figures 5 and 6 with <br />Stationing shown in Drawing 3. <br />3. Existing track gradients in the area that will be affected by 9 -East are between 1.5% and 2.0%. <br />These will be mitigated to less than 1.5% by re -ballasting. <br />4. The recommended increase in ballast height and ballast prism width is not expected to require <br />placement of fill or ballast in Fish Creek or its AVF. <br />5. Both of the two remedial methods outlined in this report have been successfully implemented <br />during undermining of the Energy Spur. There is every reason to conclude that they will <br />continue to be successfully applied to remediating subsidence associated with extraction of 9 - <br />East and the remaining panels. <br />7 PN: 2016-10 <br />