2021-02-05_PERMIT FILE - C1980007A (5)

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Subsidence Evaluation for the Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 3 2.0 MINING METHOD The longwall mining method has and will continue to be utilized in the Southern Panels, Apache Rocks West, and Sunset Trail mining areas. The projected longwall panels designs are similar to the B-seam and E-seam longwall panels mined to date in the West Elk Mine, where subsidence measurements were used to obtain the baseline data that were used in this report. A range of 8 to 141 feet of coal will be extracted from the E-seam in the Southern Panels mining area. The four longwall panels in the Sunset Trail mining area (SS1 through SS4) are proposed to have an extraction thickness ranging from 9 to 14 feet. The extraction thicknesses are projected based on exploration drillhole data; actual thicknesses may vary depending on mining conditions encountered,but will not be greater than 14 feet. E-seam longwall panels E1 to E8 were approximately 1,080 feet wide and extended up to approximately 15,000 feet in length. Panel E9 is projected to be 1,080 feet wide and approximately 3,200 feet long. Panel E14 is projected to be 1,080 feet wide and approximately 3,300 feet long. The longwall panels will be mined by the retreat longwall mining method. Panels E1 to E8 were longwall mined from east to west as panel E14 will be. Panel E9 is planned to be longwall mined from south to north. The trend of panels E1 to E8 is approximately N80°W. Projected panel E9 trends roughly N100E and E14 trends approximately N60°W. The overburden depth above the longwall panels E1 to E4 ranged from roughly 375 to 1,800 feet, whereas, the overburden depth for longwall panels E5 to E8 ranged from approximately 500 to 1,800 feet. The overburden above the longwall panel blocks of E9 and E14 ranges in thickness from approximately 260 to 740 feet. B-seam mining in the Southern Panels mining area will occur in panels B26 to B29,and will follow the same orientation as the overlying previously mined E-seam longwall panels. The longwall panels are projected to be approximately 1,080 feet wide with lengths varying from 11,500 feet up to 14,800 feet, and mining thicknesses from 9 feet up to 14 feet. In the original Exhibit 60 (May 1995), MCC anticipated two-seam mining in the B- and E-seam in the Apache Rocks West mining area. MCC has already mined the B-seam in this area (B 12, B13, and B13-A); however, the layout of the E-seam panels (E10 to E12) has shifted from being stacked over the B-seam panel to being offset. Panels E 10 to E 12 are projected to be approximately 850 to 1,080 feet wide and vary in length from approximately 3,800 feet to 5,300 feet. The mining thickness is anticipated to vary from 10 to 14 feet. E-seam mining in the Sunset Trail mining area will occur in Panels SS 1 to SS4 as shown in Figure 1. Panels SS to SS4 are projected to be approximately 1,080 feet wide with maximum lengths ranging from approximately 7,200 feet up to 9,400 feet. The panels are and will be oriented parallel to panels E1 to E8. The mining thickness is anticipated to vary from 10 to 14 feet. The 1 Practically speaking,the maximum mining height with the current longwall is 13.5 feet;however,WWE is using 14 feet in our analysis to be conservative,except with the computer modeling. 2 All of the panels discussed in this exhibit are approximately 1,080 feet wide. When evaluating subsidence,a total extraction width of 1,120 feet was used to include the entries parallel and adjacent to the longwall panel block. 831-032.912 Wright Water Engineers, Inc. December 2020