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Rest E/k Mine: Subsidence Evaluation oJthe Revised Mine Pane! <br />Lavnuts in Section 2 / and Sections 2h and 27 P Qp~ <br />• original and revised configurations. 'The following pazazneters were also <br />compazed with values derived from the conceptual model, as calibrated from the <br />West Elk Mine subsidence network as described in Exhibit 60 prepazed for the <br />Colorado Department of Minerals and Geology for the Apache Roclcs Permit <br />Revision: <br />A. Maximum vertical displacement (subsidence) from computer model <br />results were about equal to the average of the range of maximum values <br />from conceptual model calculations in both the original and revised panel <br />configurations. <br />B. Maximum tilt values from the computer model were within the range of <br />maximum values calculated from the conceptual model. <br />C. Maximum positive and negative horizontal strain from the computer <br />model were within the range of maximum values calculated from the <br />conceptual model. <br />III. Evaluation of longwall mining panel boundaries in their original and revised <br />configurations. The panel boundaries in Section 21 do not change orientation, <br />only position, and thus, should not change subsidence effects at all. The panel <br />end boundaries in Sections 26 and 27, however, change from essential straight in <br />the original configuration to an echelon in the revised configurations. <br />I have only limited field experience on how subsidence effects, such as length, width, <br />distribution of surface cracks, will compaze in the original and revised configurations. <br />However, the echelon configuration of the panel end boundaries should not increase <br />subsidence effects compazed to straight boundaries. On the contrary, the echelon pattern <br />may reduce subsidence effects because the straight portions of the solid-coal barriers are <br />significantly less than the solid-coal barrier where all the panel ends aze aligned, and <br />therefore, may cause a reduced amount of flexure of the overlying strata. <br />WY,ght Water ginerr; lnc. 83 •031.130 <br />