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West Elk Mine <br />rapid, uniform mining beneath streams and other sensitive features causes minimum mining <br />impact. _ <br />The duration of subsidence above room-and-pillar mines; however, is less predictable because <br />not all pillars are removed. For example, in Figure 9 of Exhibit 60B, subsidence at a given point <br />(p) was only about 60 percent complete after mining was completed within the area of influence <br />of the point. <br />Results of Computer Modelin <br />A computer software package was used to model the results of subsidence measurements at West <br />Elk Mine and to project subsidence amounts in the Apache Rocks and Box Canyon mining areas. <br />The package used is entitled "Comprehensive and Integrated Subsidence Prediction Model <br />(CISPM)," Version 2.0, by Syd S. Peng and Yi Luo, Department of Mining Engineering, College <br />of Mineral and Energy Resources, West Virginia University, Morgantown, WV. This program <br />performed an influence function analysis and best fit of the West Elk Mine subsidence data. The <br />fit between the data points and the influence function output from the model are shown in <br />Figure 6, Exhibit 60B. Considering that there was some F Seam influence on the B Seam <br />subsidence data, the actual subsidence measurements and subsidence profiles predicted by the <br />influence function model compare favorably. <br />Baseline subsidence measurements in the current West Elk Mine subsidence monitoring area <br />were selected such that subsidence parameters from longwall mining in the B Seam were <br />• obtained with as little influence from prior room-and-pillar mining as possible. In this way, the <br />longwall mining subsidence parameters from the monitoring area could be used to most <br />accurately project longwall mining subsidence parameters into the SOD mining area. The <br />baseline subsidence measurements selected for both conceptual modeling and computer <br />modeling were October 1991, which was before B Seam Iongwall mining began and after F <br />Seam room-and-pillar mining was completed in the subsidence monitoring network area. <br />Once the computer program was calibrated to the West Elk Mine subsidence data, subsidence was <br />projected into the SOD mining areas using representative coal extraction thicknesses and <br />overburden depths for the respective panels in order to obtain an independent check on the <br />subsidence projections based on the conceptual model (Table 1 and Figure 7, Exhibit 60B). <br />Apache Rocks and Box Canvon Mining Areas - Comparison of the two models shows that <br />subsidence values above the chain pillars and panel centers of the computer model for the Apache <br />Rocks mining area are approximately at the median point of the conceptual model data presented <br />for the eastern and western panels (Table 2 and Figures 7a and 7b, Exhibit 60). Subsidence above <br />the chain pillars and panel centers for the Box Carryon mining area is also at about the median point <br />of the conceptual model for the first four panels (Table 3 and Figure 7C, Exhibit 60). <br />South of Divide Mining Area - Comparison of Mr. Dunrud's coneeptu, l model calculations and <br />the influence function computer model of Pena, and Luo (which were done by the W WEs staff in - <br />Figures 7 and 8, Exhibit 60B) shove the following: <br />1. Maximum vertical displacement (subsidence) above the chain pillars in the transverse profile <br />10 (Figure 7, Exhibit 60B) is close to the maximum values predicted in the conceptual model <br />2.05-137 Revised June 2003 PRIG, Rev..vfarch 2006; May '006 PRIO. Nov. 2006TR107,.4p7-il 2007TR108; Sep. 2007 PR12; Feb. 2008 PR-12