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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 />2.2. Subsidence Prediction <br />Twentymile Coal, LLC has developed an extensive subsidence database from monitoring longwall <br />panel extraction from the Wadge Seam in the Southwest, Eastern, Northern, and Western mining <br />districts of the Foidel Creek Mine. This data has been submitted to the Colorado Division of <br />Reclamation, Mining and Safety (CDRMS) in semi - annual subsidence reports and in reports <br />attached to permit documents. <br />Twentymile Coal, LLC has supplemented these published data with results from monitoring the <br />county road, power lines, the Energy Spur railroad track, and both Foidel and Fish Creek AVFs <br />which interacted with the Southwest Mining District and crossed the Eastern, Western and <br />Northern Mining Districts of the Foidel Creek Mine's Wadge seam. <br />The process of incorporating these prior data in the current predictions is described in the following <br />paragraphs: <br />1. Figure 2 was compiled from records of maximum subsidence from the Southwestern <br />and Eastern mining districts and shows the relationship between maximum subsidence <br />and the width /depth ratio for Wadge seam workings at the Foidel Creek mine. <br />Subsidence from second seam mining is anticipated to be about 5% higher (when <br />expressed as a percentage of extracted seam height) in magnitude than experienced <br />when the initial, Wadge Seam was mined; the upper curve in Figure 2 represents this <br />condition. The upper curve in Figure 2 was used to predict maximum subsidence <br />values for the 985 -feet wide panels at depths between 1,000 -feet and 1,800 -feet, which <br />represents the range in conditions for affected structures in the study area. <br />2. Time phased data from the initial surveys of Panels 1, 2, and 3 in the Southwestern <br />Mining District (SubTerra, 19963) of the Foidel Creek mine, representing the surface <br />response to the first, second, and third panel extraction, were used to predict the effects <br />of initial and subsequent panel extraction. These data are contained in the semi - annual <br />reports and in permit submittals for the Foidel Creek Mine. <br />3. Subsidence over the rigid -yield pillars separating adjacent longwall panels was <br />estimated using the data from the Fish Creek study at the Foidel Creek. Mine (SubTerra, <br />1999) and data gathered during mining Panels 9, 8, and 7 -Right in the Eastern Mining <br />District and Panel 19 -Right in the Northern Mining District at the Foidel Creek Mine's <br />Wadge seam. <br />4. The Start Room and End Room profiles for all panels were estimated using data from <br />monitoring lines 1000 and 3000 in the Fish Creek study area (SubTerra, 1999) again at <br />the Foidel Creek mine. These data are contained in the semi - annual reports and in <br />permit submittals. <br />Subsidence predictions have been made for overburden thickness ranging from 1,000 to 1,800 - <br />feet representing the range of conditions in the study area. The results of these predictions are <br />contained in Figures 3, 4, and 5. Summary data include: <br />• Maximum subsidence of 70 to 75 inches for the initial and subsequent longwall panels <br />located at a depth of 1,000 -feet. <br />• Maximum subsidence of 63 inches for longwall panels located at a depth of 1,400 -feet. <br />• Maximum subsidence of 45 inches for longwall panels located at a depth of 1,800 -feet <br />4 PN: 2013 -26 <br />