Laserfiche WebLink
West Elk Mine <br />• Subsidence Survev-2.05.6(6)(b)/iii)(A) & (6)(e) <br />The following information documents subsidence processes that have been observed from studies <br />above longwall mining panels in the current West Elk Mine pemnit azea. The subsidence data obtained <br />in the current West Elk Mine azea have been used to project subsidence processes, amounts, and effects <br />into the Apache Rocks, as well as Box Canyon in the B Seam, and South of Divide mining azeas where <br />only the E Seam coal is to be mined. These data have been used to calibrate the subsidence prediction <br />models described above. <br />In addition to relying on actual subsidence data, WWE has concluded that many of the findings <br />pertaining to subsidence and probable hydrologic consequences from previous permit revisions apply <br />to the South of Divide permit revision and mining azea. The basis for this conclusion is as follows: <br />• Comparison of lithologic data from boreholes in the Jumbo Mountain, Apache Rocks and Box <br />Canyon mining azeas show consistency in the B Seam overburden materials, including those units <br />immediately above and below the E Seam coal. While duect correlation of lithologic units, <br />excluding coal beds, is generally difficult, comparison of lithologic logs shows very similar <br />alternating sequences of shales, claystones, and sandstones. Based on the stratigraphic and <br />lithologic information obtained from drill holes in the South of Divide mining azea, the rocks <br />consist of a greater proportion of shales, siltstones, and claystones than aze present in the Apache <br />Rocks and Box Canyon mining areas. <br />• The South of Divide permit revision area is topographically similaz to the Apache Rocks and Box <br />. Canyon mining areas although with a less extreme range of topographic relief. The elevation range <br />across the South of Divide permit revision area is from about 7,000 feet to approximately 8,400 <br />feet with fewer abrupt elevation changes than those seen in the Apache Rocks and Box Canyon <br />permit azeas, such as between the Sylvester Gulch drainages and West Flatiron. Like these two <br />previously permitted azeas, the South of Divide permit revision area contains gentle as well as steep <br />slopes malting it susceptible to rockfalls and landslides. <br />• Expected subsidence characterisfics of the South of Divide permit revision area, based on lithology <br />and topography, do not vary significantly from previous evaluations for B Seam mining according <br />to Mr. Dunrud, with the obvious exception of the reduced overburden thicknesses associated with <br />mining of the E Seam. Overburden thickness impacts will be discussed later in this section. <br />Based upon these similarities, much of the information contained within the documents pertaining <br />to the Apache Rocks and Box Canyon permit revision azea is applicable to the South of Divide <br />permit revision area. Where differences occur, discussions of the resulting effects have been <br />provided. <br />Inventory of Structures and Renewable Resource Lands - 2.05.6 (6)(a)(i & ii) <br />In order to ascertain the impacts that subsidence will cause on structures and renewable resource <br />lands, an inventory of these features was conducted. Projected impacts to surface and ground water <br />resources are presented later in Section 2.05.6(3). These water resources aze shown on Map 37. <br />MCC's hydrologic monitoring stations are shown on Map 1 of Exhibit 71 and the many trails and <br />U.S. Forest Service roads utilized to access these sites aze shown on Maps 67 and 68. <br />1.05-/07 Revised June 1005 PR70, Rev. March 1006; Rev. Apri! 1006 PR/0; May 1006 PR/0 <br />