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-59- <br />WECC originally proposed a basic subsidence control scenario <br />emphasizing data collection during the first five-year permit <br />period. The results of the first five year's collection will then <br />be utilized to finalize design of subsidence control specifics in <br />later permit periods. WECC acknowledges that subsidence will occur <br />but proposes to prevent damage to significant permit area features <br />such as the Dry Fork of Minnesota Creek, and Beaver and Minnesota <br />Reservoirs, by utilizing a limited extraction plan beneath these <br />critical features. In addition, extraction will be limited to <br />development beneath the landslide body delineated above the <br />Somerset townsite. Exhibit 3.4.S.A, in its amended form states "a <br />detailed analysis of the slope stability, incorporating the <br />influence of subsidence on the stability of the landslide, will be <br />performed prior to pillar robbing beneath the landslide. This <br />analysis shall be submitted to MLRB for approval before pillar <br />recovery begins". (page 30, exhibit 3.4.8.A) <br />The subsidence evaluation prepared by WECC reflects the current <br />state-of-the-subsidence-prediction-art. It includes an analysis of <br />pillar strength in areas proposed for protection by limited <br />extraction without pillar recovery upon retreat. The originally <br />approved WECC plan also included the installation and monitoring of <br />the subsidence monitoring network over the first panel to be fully <br />mined, during the third year of the first five-year permit period. <br />Data from this monitoring network is to be utilized to verify the <br />design of the buffer zones proposed beneath the Dry Fork of <br />Minnesota Creek and to predict the magnitude of subsidence and <br />subsidence phenomena to be expected throughout the remainder of the <br />lease property. Additional future subsidence monitoring networks <br />shall also be proposed for the Dry Fork area to assure that <br />subsidence impacts are prevented. <br />As a portion of its November, 1984 permit revision application, <br />WECC proposed a relocation of the originally required subsidence <br />test panel and accompanying subsidence monitoring network. <br />Reconfiguration of the underground mine plan, necessitated by an <br />approved reorientation of the mains to avoid an area of bad coal <br />and roof conditions, has resulted in a need to relocate the first <br />panel to be subsided. The relocation is not significant, allowing <br />the originally installed ground water monitoring wells to serve <br />their original purpose, monitoring ground water response to <br />subsidence of the test panel. However, the surface subsidence <br />monument locations require amendment. The amended monitoring <br />network is depicted in Figures 7, 8 and 9 of Appendix A to WECC's <br />November, 1984 permit revision application. A row of monuments <br />installed parallel to the axis of the test panel will be spaced on <br />100-foot centers. Two rows of monuments will transect the test <br />panel and will be spaced on nominal 50-foot centers. These <br />transverse monument rows will extend to the east of the panel <br />centerline above the mains and to the west for at least 750 feet to <br />the west of the panel centerline. WECC will tie the monitoring to <br />