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West Elk Mine <br />Subsidence Control Plan - 2.05.6 (6)(b) (iii) (B), (6)(d) (i& ii), (6) (e) (iv) & (6)(1)(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 <br />mining method is planned for the SOD, Apache Rocks West, Southern Panels and Sunset Trail <br />mining areas. A general east -west panel layout, is planned except for the E-seam longwall panels <br />LWE16 and LWE17 that will be in a north -south orientation. Although longwall mining may <br />initially induce more caving and fracturing of the roof rocks, it offers the advantages of maximizing <br />resource recovery. The longwall method also causes more uniform subsidence (full extraction of <br />panel) and causes equilibrium conditions to be reached in a shorter period of time (i.e., there is no <br />additional, lingering pillar crushing in panels). See further discussions in the current version of <br />Exhibit 60E. <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 <br />shallow, unconsolidated and saturated cover. Such was the case in October 2020 when <br />developing main entries under South Prong Creek. To avoid similar issues in the future, MCC <br />has performed an analysis of the minimum depth of cover required for development mining in <br />the West Elk Mine to avoid the potential for this type of surface subsidence impacts. MCC will <br />adhere to the recommendations for development mining beneath perennial streams as detailed in <br />Appendix A of Exhibit 60E. <br />Preventive Measures — 2.05.6(6 ( (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 <br />offers 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 <br />panels. (As mining approaches the ditch, the pre -mining condition of the ditch will be <br />documented in a pre -subsidence survey. This survey will be added to the permit application in <br />the semi-annual subsidence reports. Before, during and after mining, the amount of the ditch that <br />is subsided will be determined by surveying reflector stations in the ditch, as set forth in Section <br />2.05.6(6) (c). In addition to the surveying, changes in the ditch caused by subsidence will be <br />detected by visually inspecting the ditch on a weekly basis while active longwall mining is <br />within 1000 feet of the ditch. MCC will repair any mining -caused damage found during the <br />monitoring or during visual inspections, in accordance with the agreement between MCC and the <br />Minnesota Canal and Reservoir Company. If mining activity disrupts flow in the ditch, MCC <br />will apply methods set out in the subsidence mitigation plan or injured parties will be <br />compensated with water resources that are owned by MCC per its adjudicated water <br />augmentation plan.. These water resources are identified in Exhibit 52. <br />2.05-120 Rev. 06105- PRIO, 03/06- PRIO, 05/06- PRIO, 11/060- TRI07, 04/07- TRI08, 09/07- PR12, 02108- PR12; 11/10- A/R372; 10%20- MR-452; <br />12/20- TR149' 12,21- TRI50 <br />