Laserfiche WebLink
West Elk Mine <br /> <br />2.05-110 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; <br /> 12/20- TR149; 12/21- TR150, 1/24-TR152 <br />Southern Panels, Dry Fork, SOD and Sunset Trail Mining Areas <br />The longwall mining method was and will continue to be utilized in the Southern Panels, Dry <br />Fork, SOD and Sunset Trail mining areas. Refer to Exhibit 60E for the most current panel <br />designs and subsidence modelling parameters. <br />In addition, retreat mining will be utilized in the Sunset Trail mining area. Refer to Exhibit 84 for <br />the most current mining location, modelling parameters and subsidence predictions. <br />Geologic Factors Influencing Subsidence - 2.05.6 (6)(e)(i)(B) <br />Subsidence is influenced by the local geology in the following ways: geologic structure, strength <br />and behavioral properties of the rocks, stratigraphic sequence, and moisture content. See the <br />Exhibit 60 through 60E series for further discussions on this topic. <br />Field Recognition of Subsidence and Non-subsidence Features in the West Elk Mine Area <br />There are four different types of features that have been observed in the West Elk mining area: <br />(1) Subsidence cracks and bulges, (2) Construction cracks, (3) Desiccation cracks, and (4) <br />Gravity-induced tension cracks. They can be distinguished easily in some areas where, for <br />example, no mining has occurred in that area. In other areas they may be difficult to distinguish, <br />such as in areas that have been mined, but where conditions are also favorable for construction, <br />desiccation, or gravity-induced tension cracks to occur. See the discussions of theses topics in <br />the Exhibit 60 through 60E series. <br />Subsidence Prediction Based on Local Mining Experience - 2.05.6 (6)(e)(i)(C) <br />As is discussed in the most current version of Exhibit 60E, much information has been gathered <br />regarding subsidence at West Elk Mine due to local mining of the F Seam (room-and-pillar <br />method) and B and E seams (longwall method). Subsidence monitoring of a grid network was <br />conducted from1985 to 1997 and provided considerable data regarding the effects of varying <br />overburden thicknesses, mining heights, and mining methods on the subsidence network. The <br />grid verified MCC’s predicted subsidence, and established when subsidence occurs, where it <br />occurs, and when it is complete. The grid demonstrated that the majority of longwall mining <br />subsidence was seen within the first year after mining, and in most cases subsidence was <br />completed within 12 to 18 months. <br />Detailed Description of Predicted Subsidence Phenomena – 2.05.6 (6)(e)(i)(D) <br />As is discussed in the most current version of Exhibit 60E, subsidence, as it relates to mining, is <br />defined as the local downward displacement of the surface and the overburden rock in response to <br />mining under the influence of gravity. General discussions of the various zones defined within the <br />subsidence area; predicted maximum vertical and horizontal displacements, tilt, curvature and <br />horizontal strain; predicted zones of tensile strain related to mine geometry; predicted rates and <br />duration of subsidence; the effects of topography on subsidence; and the predicted angle of draw are <br />summarized in the Exhibit 60 through 60E series.