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Subsidence Evaluation for the <br />Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 23 <br /> <br />831-032.923 Wright Water Engineers, Inc. <br />December 2021 <br />WWE further calibrated the computer model using subsidence monitoring data collected over E- <br />seam panels E1 to E3. While the model over predicted the subsidence over panel E1, the previous <br />calibration accurately predicted the subsidence along the Dry Fork survey points. Therefore, <br />WWE elected to use the more conservative parameters, recognizing the model results may over- <br />predict subsidence. <br />Once the computer program was calibrated to the West Elk Mine subsidence data, subsidence was <br />then projected into Southern Panels, Apache Rocks West, and Sunset Trail mining areas using <br />representative coal extraction thicknesses and overburden depths for the respective panels in order <br />to obtain an independent check on the subsidence projections based on the conceptual model. <br />Comparison of the Dunrud’s conceptual model calculations and the influence function of the SDPS <br />computer model (which were done by WWE in Figures 7, 7A, 8, and 9) show the following: <br />1. Maximum vertical displacement (subsidence) above the chain pillars in the transverse <br />profile (Figures 7 and 7A) is close to the maximum values predicted in the conceptual <br />model calculations. Maximum vertical displacement above the longwall panel centers, <br />however, is about equal to the median values projected in the conceptual model <br />calculations. <br />2. The ranges calculated for vertical displacement in the conceptual model are conservative. <br />The ranges account for rapidly changing overburden thicknesses in the local rugged terrain <br />of the Southern Panels, Apache Rocks West, and Sunset Trail mining areas and for <br />changing lithology—such as lenticular sandstones, coal seams, and shales—in the <br />overburden rocks.