Laserfiche WebLink
Subsidence Evaluation for the <br /> Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 23 <br /> WWE further calibrated the computer model using subsidence monitoring data collected over E- <br /> seam panels El to E3. While the model over predicted the subsidence over panel El,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. <br /> 831-032.912 Wright Water Engineers, Inc. <br /> December 2020 <br />