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West E(k Mine: Subsidence Evaluation ojthe Revised Mine Pane( <br />/.m~ours in Secrinn 2/ and Sections 2h and 17 Pnge h <br />• The trapezoidal shape of the pillazs on the west end of the panels in Sections 26 and 27 <br />under the revised panel configuration will likely be stronger than their rectangular <br />counterparts under the original plan, because the trapezoidal pillars are lazger. <br />SUMMARY <br />In summary, based on my foregoing review and analysis of the original and revised <br />longwall panel configurations in Section 21 and in Sections 26 and 27, I do not believe <br />that the revised panel configuration as proposed by Mountain Coal Company will change <br />the effects of subsidence as compared to those projected in Exhibit 60 of the Apache <br />Rocks Permit Revision. <br />CONCLUSION <br />The computer model, CISPM, was used to predict the vertical displacement (subsidence), <br />• tilt, and strain resulting from the original and revised longwall panel layouts. The model <br />showed that the maximum values of the pazameters aze not expected to change <br />significantly with the revised panel layout. <br />Mr. Rich Dunrud provided an independent check of the computer model using his <br />conceptual model developed in Exhibit 60 of the Apache Rocks Permit Revision. His <br />review found the model predictions to be within the range predicted by his analyses. In <br />' addition, he concluded that changes in subsidence effects, such as surface cracking, are <br />expected to be very minor with the revised panel layout. <br />C:\831-032\250ardUtepon. doc <br />• <br />Wng r 'ater Engineers, /nc. 831-033.7 <br />