2009-06-09_PERMIT FILE - C1980007A (2)

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West Elk Mine Subsidence Survey - 2.05.6(6)(b)(iii)(A) & (6) (e) The following information documents subsidence processes that have been observed from studies above longwall mining panels in the current West Elk Mine permit area. The subsidence data obtained in the current West Elk Mine area have been used to project subsidence processes, amounts, and effects into the Apache Rocks, as well as Box Canyon in the B Seam, and South of Divide mining areas where only the E Seam coal is to be mined. These data have been used to calibrate the subsidence prediction models described above. In addition to relying on actual subsidence data, WWE and TetraTech have concluded that many of the findings pertaining to subsidence and probable hydrologic consequences from previous permit revisions apply to the South of Divide with the Dry Fork Lease permit revision and mining area. The basis for this conclusion is as follows: Comparison of lithologic data from boreholes in the Jumbo Mountain, Apache Rocks and Box Canyon mining areas show consistency in the B Seam overburden materials, including those units immediately above and below the E Seam coal. While direct correlation of lithologic units, excluding coal beds, is generally difficult, comparison of lithologic logs shows very similar alternating sequences of shales, claystones, and sandstones. Based on the stratigraphic and lithologic information obtained from drill holes in the South of Divide mining area, the rocks consist of a greater proportion of shales, siltstones, and claystones than are present in the Apache Rocks and Box Canyon mining areas. The South of Divide and Dry Fork pen-nit revision area is topographically similar to the Apache Rocks and Box Canyon mining areas although with a less extreme range of topographic relief. The elevation range across the South of Divide permit revision area is from about 7,000 feet to approximately 8,400 feet with fewer abrupt elevation changes than those seen in the Apache Rocks and Box Canyon permit areas, such as between the Sylvester Gulch drainages and West Flatiron. Like these two previously permitted areas, the South of Divide permit revision area contains gentle as well as steep slopes making it susceptible to rockfalls and landslides. • Expected subsidence characteristics of the South of Divide permit revision area, based on lithology and topography, do not vary significantly from previous evaluations for B Seam mining according to Mr. Dunrud, with the obvious exception of the reduced overburden thicknesses associated with mining of the E Seam. Overburden thickness impacts will be discussed later in this section. Based upon these similarities, much of the information contained within the documents pertaining to the Apache Rocks and Box Canyon permit revision area is applicable to the South of Divide permit revision area. Where differences occur, discussions of the resulting effects have been provided. Inventory of Structures and Renewable Resource Lands - 2.05.6 (6)(a)(i & ii) In order to ascertain the impacts that subsidence will cause on structures and renewable resource lands, an inventory of these features was conducted. Projected impacts to surface and ground water resources are presented later in Section 2.05.6(3). These water resources are shown on Map 37. MCC's hydrologic monitoring stations are shown on Maps 1 of Exhibit 71, 34, and 37. The many trails and U.S. Forest Service roads utilized to access these sites are shown on Maps 67 and 68. Table 42A, below, shows an inventory of all structures and renewable resource lands which exist in the permit area and adjacent area. Water-bearing bedrock stratigraphic units are not considered to be aquifers in the permit and adjacent area (Section 2.04.7(1)); therefore, renewable resource lands are not associated with these units. More site-specific discussion of various areas follows the table. 2.05-107 Revised 06105, 03106, 04106 & 05106- PR10;11/06- TR107; 09107& 02108-PR12; 04109- TR117