Laserfiche WebLink
West Elk Mine <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 />Hinhway 133 Landslides in Relation to Anple of Draw Projections <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 azea, the closest State Highway 133 landslides are located <br />approximately 600 feet north of the mining azea 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 />longwall panel E9 in the South of Divide mining area (N%, Sec 32, T 13 S, R 90 W) (Dunrud, <br />1989). Overburden depth to the E Seam in that area vanes 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 azeas 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 neaz the north shore of Minnesota Reservoir in the SW'/< 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 aze located to the southeast in the SE'/a of Sec 31 and the SW'/< of Sec <br />32. <br />Landslide located neaz the southwest comer of un-mined longwall panel 8 in the N''/z of Sec 8 <br />and the S''/z 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, which were mined during the mid 1490s. Landslide movement occurred during unusually <br />wet periods before mining, during mining, and after mining and subsidence was complete. The <br />landslides located north and south of Minnesota Reservoir are similaz to those on Jumbo 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 were locally observed in both landslide azeas. <br />It is important to note that no earth tremors (seismic activity) were felt by Mr. Dunrud in all the <br />annual traverses and observations made above the longwall mining areas in the Jumbo Mountain, <br />. Apache Rocks, and Box Canyon mining areas during the last 9 years (1996 through 2004). For <br />example, no tremors were felt during the annual traverse above longwall panel 13 in 1999, when <br />1.05-/46 Revised June 1005 PR/0, Rev. March 1006; May 1006 PRIO <br />