2011-02-14_PERMIT FILE - C1980007A (3)

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Subsidence Evaluation for the Exhibit 60E South of Divide and Dry Fork Mining Areas Page 18 • 5.9 Results of Computer Modeling A computer software package was used to model the results of subsidence at West Elk Mine and to project subsidence in the South of Divide. mining area. The package used is entitled: "Comprehensive and Integrated Subsidence Prediction Model (CISPM)," Version 2.0, by Syd S. Peng and Yi Luo, Department of Mining Engineering, College of Mineral and Energy Resources, West Virginia University, Morgantown, West Virginia. This program performed an influence function analysis and best fit of West Elk Mine subsidence data. The fit between the data points and the influence function output from the model is shown in Figure 6. Considering that there was some F Seam influence on the B -seam subsidence data, the actual subsidence measurements and subsidence profiles predicted by the influence function model compare favorably. Baseline subsidence measurements in the current West Elk Mine subsidence monitoring area were selected such that subsidence parameters from longwall mining in the B -seam were obtained with as little influence from prior room - and - pillar mining as possible. In this way, the longwall mining subsidence parameters from the monitoring area could be used to most accurately project longwall mining subsidence parameters into the South of Divide mining area. The baseline subsidence measurements selected for both conceptual modeling and computer modeling were October 1991, which was before B -seam longwall mining began and after F Seam room - and - pillar mining was completed in the subsidence monitoring network area. Once the computer program was calibrated to the West Elk Mine subsidence data, subsidence • was then projected into South of Divide and Dry Fork mining areas using representative coal extraction thicknesses and overburden depths for the respective panels in order to obtain an independent check on the subsidence projections based on the conceptual model (Table 1). Comparison of the Dunrud's conceptual model calculations and the influence function computer model of Peng and Luo (which were done by WWE in Figures 7 and 8) show the following: 1. Maximum vertical displacement (subsidence) above the chain pillars in the transverse profile (Figure 7) is close to the maximum values predicted in the conceptual model calculations. Maximum vertical displacement above the longwall panel centers, however, is about equal to the median values projected in the conceptual model calculations. 2. The ranges calculated for vertical displacement in the conceptual model are conservative. The ranges account for changing rapidly changing overburden thickness in the local rugged terrain of the South of Divide and Dry Fork mining areas and for changing lithology —such as lenticular sandstones, coal seams, and shales —in the overburden rocks. 1�1 831 - 032.810 Wright Water Engineers, Inc.