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West Elk Mine <br />opinion that coal mine subsidence could not cause landslides nearly as severe as those observed <br />from the highway construction. Subsidence causes horizontal and vertical displacement of the <br />ground with attendant tilt, curvature, and strain, which may increase landslide activity on slopes that <br />are already unstable. But subsidence does not remove material from the lower parts of deposits. <br />Subsidence processes therefore do not affect the mass distribution of the deposit as did the highway <br />construction near the northern boundary of the Box Canyon permit revision area. - <br />Highway 133 Landslides in Relation to Angle of Draw Proiections <br />The northernmost longwall panel of the Box Canyon mining area, as currently planned, is located <br />about 650 to 2,700 feet south of the landslides on the south side of State Highway 133. Projecting <br />to the surface an angle of draw of 21 degrees, which is the maximum angle measured in the <br />Somerset-West Elk mining area, the closest State Highway 133 landslides are located <br />approximately 600 feet north of the mining area of influence, and therefore should not be affected <br />by longwall mining. <br />South of Divide Mining Area -An extensive landslide area is located above the northern part of <br />long-wall panel E9 in the South of Divide mining area (N%2, Sec 32, T 13 S, R 90 W) (Dunrud, <br />1989). Overburden depth to the E Seam in that area varies from 500 to 550 feet. The landslide <br />surface contains cracks, bulges, and depressions. Movement likely has occurred during the last <br />decade or so, but began many centuries ago. <br />Based on a stereographic review of July 2004 vertical aerial photographs, renewed activity <br />occurred locally in western part of the landslide areas north and south of Dry Fork during wet <br />periods in the 1980s (1984 to 1987) and the mid 1990s (1994 to 1996). The Dry Fork road was <br />taken out one half-mile west of the Minnesota Reservoir dam by this renewed movement in 1987 <br />(Map 1 of Exhibit 60). <br />Landslide located near the north shore of Minnesota Reservoir in the SW1/4 of Sec 29. This slide <br />is located on the border between the Apache Rocks and South of Divide mining areas. <br />Landslide area located on the Dry Fork road in the approximate center of Sec 31, T 13 S, R 90 <br />W. Two small landslides are located to the southeast in the SEl/4 of Sec 31 and the SW'/4 of Sec <br />32. <br />Landslide located near the southwest corner of un-mined longwall panel 8 in the N'/2 of Sec 8 <br />and the S', ? of Sec 5, T 14 S, R 90 W. <br />Some of the most important information regarding mine subsidence and mine-induced seismicity <br />was obtained from observations of active landslides on Jumbo Mountain above longwall panels 8 <br />and 9. lzich were mined during the mid 191:1s. Landslide movement occurred during unusually <br />efore miring, during mining, and after miming and subsidence was complete. The <br />landslides located north and south of Minnesota Reservoir are similar to those on Jurmbo Mountain. <br />Both occur in surficial material (rocks, gravel, sand, silt, clay, and soil) and local outcrops of <br />bedrock that have slumped and flowed downhill during periods of increased saturation. Cracks, <br />bulges, and depressions or troughs, and springs Nvere locally observed in both landslide areas. in C? <br />2.05-146 Revised June 200.1 PRIG. Rev. March 2006; ATap 2006 PR10, Nov. 2006TR1071AP7i12007TRI08;Sep. 2007 PR12; Feb. 2008 PR-12