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

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West Elk Mine 2.05-105 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 The extraction of coal from the B and E Seams in the SOD, Apache Rocks West, Southern Panels and Sunset Trail Mining areas has and will be completed using longwall mining methods. The resulting disequilibrium due to longwall mining may result in surface subsidence, dependent on a number of inter-related factors. As stated by Peng in Surface Subsidence Engineering (1992), "When total extraction is used, it produces a large void in the coal seam and disturbs the equilibrium conditions of the surrounding rock strata. The rock strata bend downward while the floor heaves. When the excavated area (gob) expands to a sufficient size, the roof strata will cave. As a result, the overlying strata continue to bend and break until the piles of the fallen rock fragments are sufficiently high to support the overhanging strata. At this time, the overlying strata no longer cave, but bend and rest on the underlying strata. Strata bending in subsidence develop upward until reaching the surface and forming a subsidence basin. The whole overburden strata and the surface subsidence basin will further go through a period of compaction and gradually become stabilized." The purpose of the Exhibit 60 through 60 E series of documents is to describe on a site-specific basis, and to quantify to the extent feasible, the various subsidence phenomena. These exhibits describe subsidence processes that have been observed from studies above longwall panels mined in the West Elk Mine and from other similar operations and studies. The subsidence information obtained from mining to date in the West Elk Mine has been used to project subsidence processes, amounts, and effects to the SOD, Dry Fork, Southern Panels, Apache Rocks West, and Sunset Trail mining areas within MCC’s permit and affected area boundaries. Also included in this section is an inventory of structures and renewable resource lands in the current permit area.The focus of Exhibit 60 was to address subsidence in the Apache Rocks and Box Canyon mining areas, Exhibit 60B and 60D were focused on the South of Divide mining area and Exhibit 60C was on the West Flatiron mining area. Subsidence Survey – 2.05.6(6)(b)(iii)(A) & (6)(e) Exhibit 60E 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 in the SOD, Dry Fork, Southern Panels, Apache Rocks West, and Sunset Trail mining areas. These data have been used to calibrate the subsidence prediction models in the Exhibit 60 through 60E series. 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 34, 37 and Map 1 of Exhibit 71. 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 that 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.