2024-06-25_PERMIT FILE - C1980007A (4)

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West Elk Mine 2.05-108 Rev. 06/05- PR10, 03/06- PR10, 05/06- PR10, 11/060- TR107, 04/07- TR108, 09/07- PR12, 02/08- PR12; 11/10- MR372; 10/20- MR-452; 12/20- TR149; 12/21- TR150, 1/24-TR152 of the near-surface strata and possible near-surface fractures associated with the predicted subsidence could reactivate or initiate landslides. Mr. Dunrud observed that many of the existing landslides, including the landslides north and south of Minnesota Reservoir became unstable and moved during the period of high precipitation in the mid 1980s. The landslides on the southeast side of West Flatiron and on the west side of Deep Creek in the Apache Rocks area appear to have been unaffected by longwall mining beneath the areas. It therefore appears apparent that wet seasons affect landslides more than does longwall mining. During very wet periods, however, landslides that are already unstable may locally be triggered by mine subsidence. The following are known locations within the present permit area, the South of Divide and Dry Fork mining areas where the reactivation of a landslide could occur as a result of future mining: South of Divide mining area: An extensive landslide located south of Minnesota Reservoir just north of projected Panels LWE16 and LWE17 in the NW¼ of Section 32. Dry Fork mining area: There are three slides identified on the Deep Creek Ditch in Section 2, of Township 14 South, Range 90 West, 6th P.M., one that warrants concern, this slide is located above the bleeder entries along the south side of Panel E 6 the other two land slides are outside the influence of mining. The slide will be monitored both visually and by survey methods. A discussion regarding the monitoring plans for the landslide located on the south abutment of the Monument Dam are included in Section 2.05.6 (6)(e)(i)(D) - Detailed Description of Predicted Subsidence Phenomena, Subsection “Effects Of Subsidence And Mine-Induced Seismic Activity On Man-Made Structures And Renewable Resources”, Monument Dam - Minnesota Reservoir. A discussion concerning the preventative measures to be employed to protect Monument Dam from mining induced impacts is contained in Section 2.05.6(6)(f)(iv)(A- D) - Detailed Description of Mitigating Measures. Presently, there are four known locations within the permit area where the reactivation of a landslide could be potentially linked to past or current mining. The first area, in Lone Pine Gulch (Section 20, T13S, R90W, 6th P.M.), contains numerous old landslide features, including steep, hummocky topography with many smaller surficial slumps. Cracking and slumping occurred on one section of a jeep trail in this area in early October 1994. The cracks appeared during mining of the 5NW longwall panel in the B-Seam. Location of the cracks coincides with the boundary of earlier F- Seam room-and-pillar panels. The second area, discussed previously, is above the 8NW longwall panel. This landslide activity, which could not be definitively linked to longwall mining, is described in considerable detail in a CDRMS inspection report (CDRMS 1996). The third area is above the 9NW longwall panel. Another known landslide area is south of Highway 133 near Box Canyon within the Box Canyon Permit revision area. These landslides are outside the projected longwall mining subsidence effects (i.e., 19 degree angle of draw) by more than 600 feet as described in Exhibit 60C, 60D and 60E. Rockfall The most current evaluations of subsidence impacts can be found in the quarterly subsidence monitoring reports each year. In past years, as discussed in Section 2.04.6, Geology Description,