Laserfiche WebLink
West Elk Mine <br /> <br />2.05-120 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, 2/25-MR486 <br />g, respectively. Barr Engineering evaluated the stability of the newly constructed dam during the <br />Summer of 2008 (see Exhibit 76) and verified that the safety factor of 1.5 and would not be <br />impacted by mining-induced seismicity. <br />Subsidence Control Plan - 2.05.6 (6)(b)(iii)(B), (6)(d)(i&ii), (6)(e)(iv) & (6)(f)(i-vii) <br />Description of Mining Methods – 2.05.6 (6)(f)(iv)( A& B) <br />As discussed in Section 2.05.6(6)(e)(i)(A), Brief Description of Mining Method, the longwall mining <br />method is planned for the SOD, Apache Rocks West, Southern Panels and Sunset Trail mining areas. <br />A general east-west panel layout, is planned except for the E-seam longwall panels LWE16 and <br />LWE17 that will be in a north-south orientation. Although longwall mining may initially induce <br />more caving and fracturing of the roof rocks, it offers the advantages of maximizing resource <br />recovery. The longwall method also causes more uniform subsidence (full extraction of panel) and <br />causes equilibrium conditions to be reached in a shorter period of time (i.e., there is no additional, <br />lingering pillar crushing in panels). See further discussions in the current version of Exhibit 60E. <br />Also as discussed in Section 2.05.6(6)(e)(i)(A), Brief Description of Mining Method, retreat mining <br />of the Sunset South Mains will be utilized in the Sunset Trail Mining area. Exhibit 84, the <br />Geotechnical Assessment For The Purpose Of Pillar Extraction Between 2 And 30 Crosscuts In <br />Sunset South Mains, dated December 27, 2023, and the Geotechnical Assessment For The Purpose <br />Of Partial Pillar Extraction Between 2 And 29 Crosscuts In Sunset Mains, dated April 22, 2024, <br />analyzes and depicts detailed mining sequences, modelling parameters, subsidence predictions and <br />minimum and maximum depths of cover for retreat mining in the Mains. <br />Although subsidence is primarily a result of the secondary recovery of coal from a longwall coal <br />panel, subsidence type features may occur when developing main entries/roadways under shallow, <br />unconsolidated and saturated cover. Such was the case in October 2020 when developing main <br />entries under South Prong Creek. To avoid similar issues in the future, MCC has performed an <br />analysis of the minimum depth of cover required for development mining in the West Elk Mine to <br />avoid the potential for this type of surface subsidence impacts. MCC will adhere to the <br />recommendations for development mining beneath perennial streams as detailed in Appendix A <br />of Exhibit 60E. <br />Preventive Measures – 2.05.6(6)(f)(iii) <br />State-of-the-art longwall mining technology will continue to be utilized for extraction of the B <br />Seam and E Seam coal within the permit area. Although longwall mining may initially induce <br />more caving and fracturing of the roof rocks, as compared to the room-and-pillar method, it offers <br />the advantages of maximizing resource recovery; more complete subsidence; equilibrium <br />conditions occurring in a shorter period of time; more uniform and predictable parameters <br />necessary for the evaluation of probable hydrologic consequences; and in general, fewer and less <br />significant adverse hydrologic impacts than room-and-pillar mining. <br />A small portion of Deep Creek Ditch may be undermined by E seam and B Seam longwall panels. <br />(As mining approaches the ditch, the pre-mining condition of the ditch will be documented in a <br />pre-subsidence survey. This survey will be added to the permit application in the semi-annual <br />subsidence reports. Before, during and after mining, the amount of the ditch that is subsided will <br />be determined by surveying reflector stations in the ditch, as set forth in Section 2.05.6(6) (c). In