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was some F Seam influence on the B Seam subsidence data, the actual subsidence measurements <br />and subsidence profiles predicted by the influence function model compare favorably. Similar <br />results would be expected for the Dry Fork mining area. <br />Baseline subsidence measurements in the current West Elk Mine subsidence monitoring area were <br />selected such that subsidence parameters from longwall mining in the B Seam were obtained with <br />as little influence from prior room-and-pillar mining as possible. In this way, the longwall mining <br />subsidence parameters from the monitoring area could be used to most accurately project longwall <br />mining subsidence parameters into the South of Divide mining area. The baseline subsidence <br />measurements selected for both conceptual modeling and computer modeling were October 1991, <br />which was before B Seam longwall mining began and after F Seam room-and-pillar mining was <br />completed in the subsidence monitoring network area. Once the computer program was calibrated <br />to the West Elk Mine subsidence data, subsidence was then projected into South of Divide mining <br />area using representative coal extraction thicknesses and overburden depths for the respective <br />panels in order to obtain an independent check on the subsidence projections based on the <br />conceptual model (Table 1). Comparison of Dunrud's conceptual model and the influence function <br />computer model of Peng and Luo show the following: <br />Comparison of Dunrud's (206, page 14) conceptual model calculations and the influence function <br />computer model of Peng and Luo (which were done by the Wright Water Engineers, Inc. in <br />Figures 7 and 8) show the following: <br />1. Maximum vertical displacement (subsidence) above the chain pillars in the transverse profile <br />(Figure 7) is close to the maximum values predicted in the conceptual model calculations. <br />Maximum vertical displacement above the longwall panel centers, however, is about equal <br />to the median values projected in the conceptual model calculations. <br />2. The ranges calculated for vertical displacement in the conceptual model are conservative. <br />The ranges account for changing rapidly changing overburden thickness in the local rugged <br />terrain of the South of Divide mining area and for changing lithology-such as lenticular <br />sandstones, coal seams, and shales-in the overburden rocks. <br />Tetra Tech - 0907171P 14