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West Elk Mine <br />resources in the area. Based on annual subsidence observations in the Jumbo Mountain, Apache <br />Rocks, and Box Canyon mining areas during the last nine years, the following information is <br />considered appropriate for the South of Divide mining area. <br />Monument Danz - Minnesota Reservoir <br />Monument Dam - Minnesota Reservoir, which provides storage water primarily for <br />irrigation, is located between two landslides-one beginning at the north shore and the <br />other beginning at the south shore. As explained above, landslide movement on Jumbo <br />Mountain occurred during unusually wet periods before mining began, during mining, and <br />after mining and subsidence was complete. The conclusions were that landslide movement <br />occurs in response to ground saturation and is not noticeably affected by subsidence and <br />seismic activity produced by longwall mining beneath, or near, landslide areas. <br />Both the landslides on Jumbo Mountain and those north and south of Minnesota Reservoir occur <br />in surficial material (loose rock, gravel, sand, silt, clay, and soil) and local bedrock outcrops. <br />The author therefore expects that the mining of longwall panel E9 will not noticeably affect the <br />large landslide south of Minnesota Reservoir. <br />Mining of the nine longwall mining panels in the South of Divide mining area, as currently <br />planned, will not affect Minnesota Reservoir. The reservoir is located outside the area of mining <br />influence, using the most conservative 45-degree angle of draw. Measured ground subsidence <br />will not affect Monument Dam and Minnesota Reservoir, however, seismicity caused by <br />longwall mining is possible and could affect the dam, reservoir and the landslide abutting the <br />dam. <br />Water Resources <br />Stock Watering Ponds and U.S. Forest Service <br />The stock watering ponds in the South of Divide mining area are located in debris flows or <br />colluvium derived from the debris flows (Dunrud 1989). A total of 14 ponds have been mapped in <br />the South of Divide mining area (for more information see Section 2.2 of Exhibit 71). Ten of these <br />ponds are also classified as U.S. Forest Service water resources. The ponds in the permit area are <br />photographed on the ground on an annual basis beginning in 2005. The debris flows consist of a <br />heterogeneous mixture of clay derived from the Wasatch Formation and boulders and gravels <br />derived primarily from the Mount Gunnison intrusive (granodiorites and quartz monzanites). Based <br />on observations made during geologic mapping in the area, these debris flows are even less likely to <br />be affected by longwall mining than the alluvium The debris flows have a very low permeability <br />and, because the clay matrix is armored by the interstitial gravel and boulders, are resistant to <br />erosion (the Dee; Creel: Ditch locally flows in this material at steep gradients). Based on the <br />above-mertier,ed niIlsei7 auens. no effects are expected `when ponds in the South of Divide mining <br />area are undermined. The clay-rich material that lines these ponds is expected to provide a seal <br />against any subsidence effects. Stock watering ponds conditions -,vill be sur-Naeyed, when accessible, <br />before they are Nvithin twice the angle of draw. A second sur-?I 7 ey will be conducted within three <br />months after they are no longer in the angle of draw. <br />2.06-150 Revised Jame 2006 PR 10. Rev. AIarch 2006; allay 2006 PRIO, .Nov. 2006TR107,.4p7•il 2007TR108;Sep. 2007 PR12; Feb. 2008 PR-12