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~• Rate and duration of subsidence above longwall mining panels, therefore, are a function of mining rate. The faster and more uniformly the longwall mining occurs, the less time any surface cracks present will be open to potentially impact surface or ground water. The duration of subsidence above room-and-pillaz mines; however, is less predictable because not all pillars aze removed. For example, in Figure 8 of Exhibit 60, subsidence at a given point (p) was only about 60 percent complete after mining was completed within the area of influence of the point. Results of Computer Modeling A computer softwaze package was used to model the results of subsidence measurements at the West Ells Mine and to project subsidence amounts in the Apache Rocks and Box Canyon mining azeas. The package used is entitled "Comprehensive and Integrated Subsidence Prediction Model (CISPM)," Version 2.0, by Syd S. Peng and Yi Luo, Department ofjMining Engineering, College of Mineral and Energy Resources, West Virginia University, Morgantown, WV. This program performed an influence function analysis and best fit of the West Elk Mine subsidence data. The fit between the data points and the influence function output from the model are shown in Figure 6, Exhibit 60. 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. • Once the computer program was calibrated to the West Elk Mine subsidence data, subsidence was projected into the Apache Rocks and the Box Canyon mining areas for the various overburden depths and mining sequences in order to obtain an independent check on the subsidence projections based on the conceptual model (Table 1 and Figure 6, Exhibit 60).~ Comparison of the two models shows that subsidence values above the chain pillars and panel centers of the computer model for the Apache Rocks mining area aze approximately at the median point of the conceptual model data presented for the eastern and western panels (Table 2 and Figures 7a and 7b, Exhibit 60). Subsidence above the chain pillars and panel centers for the Boz Canyon mining azea is also at about the median point of the conceptual model for the first fourl,panels (Table 3 and Figure 7C, Exhibit 60). The conceptual model subsidence prediction results ace presented in ranges that make it more conservative than the computer model results. Effects of Topogranhv on Subsidence Processes In contrast to subsidence of rock units behaving asfixed-end, laterally constrained, multiple plates, subsidence in steep topography will typically occur Cnon-fixed end, laterally unconstrained multiple plates (rock units). This lack of lateral confinement may locally cause: • Reversals of horizontal displacement and excessive tensile ;strain on steep slopes. Peng and Hsuing (1986) found that horizontal displacement is affected by slopes greater than 20 percent. Displacements on steep slopes and cliffs can cause cracks to open more along • faults, fractures, and joints than would occur in subdued top,'ography where the rock units are 2.05-123 March 2005PR1 / f .~ 'l