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Subsidence Evaluation for the <br />Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 15 <br /> <br />831-032.923 Wright Water Engineers, Inc. <br />December 2021 <br />alignment of the E-seam panels from the B-seam panels, the maximum subsidence <br />over E-seam panel E12 will have very little influence from the B-seam mining in <br />panel B13-A. <br />Sunset Trail Mining Area: Overburden depth above the centers of the projected E-seam longwall <br />panels ranges from approximately 350 to 1,250 feet. With a projected longwall panel width of <br />1,080 feet, and assuming that the chain pillars (gate road pillars) are similar to those in longwall <br />panel B17 of the Apache Rocks mining area, maximum subsidence (vertical displacement Sm = a <br />• t) is predicted as follows (Table 4) for panels SS1 through SS4: <br />• Panels SS1 to SS4: These panels range from subcritical to supercritical (width-to-depth <br />ratio (W/d) ranges from 0.86 to 3.09). <br />1. Maximum vertical displacement above the chain pillars (Scp) is expected to range <br />from 0.9 to 2.7 feet (0.1 to 0.3t) where the extraction thickness is 9 feet, and 1.4 to <br />4.2 feet where the extraction thickness is 14 feet. <br />2. Maximum vertical displacement (subsidence, Sm = a • t) is projected to range from <br />5.4 to 7.2 feet (0.6 to 0.8t) where the extraction thickness is 9 feet, and 8.4 to 11.2 <br />feet, where the extraction thickness is 14 feet. <br />5.3.1.2 Maximum Tilt <br />Maximum tilt (Mm) was calculated from differential vertical displacements at the West Elk Mine <br />monitoring network in terms of the ratio of maximum vertical displacement to overburden depth <br />(Sm/d in dimensionless units L/L) (Table 1 and Figure 5). Tilt values at West Elk Mine range from <br />1.4 to 2.1 percent. Maximum calculated tilt ranges from about two to three times Sm/d (2 to <br />3⋅(Sm/d)) at West Elk Mine. Maximum tilt in the Southern Panels, Apache Rocks West, and Sunset <br />Trail mining areas is projected to range from 2.2 to 2.3 Sm/d. Maximum tilt in four different mining <br />areas studied by Dunrud in the Western United States ranges from 2.5 to 5⋅(Sm/d). <br />Southern Panels Mining Area: <br />As stated earlier in this report, tilt above the nine E-seam longwall panels (panels E1 to E8 and <br />E14 to E17) are projected to range between 2.2 and 2.3 Sm/d for coal extraction thickness ranging <br />between 9 and 14 feet. These values are based on subsidence measurements at West Elk Mine <br />(Table 1, Figure 5). The overburden depth above the longwall panel centers ranges from 360 to <br />1,425 feet (Table 2). <br />• Panels E1 to E8 and E14 to E17: Maximum tilt in these panels is projected to range from <br />0.008 to 0.046 (0.8 to 4.6 percent) where 9 feet of coal is extracted, and from 0.013 to <br />0.072 (1.3 to 7.2 percent) where 14 feet of coal is mined (Table 2). <br />Similarly, tilt above the longwall panels (panels B26 to B29) are projected to range between 2.2 <br />and 2.3 Sm/d for coal extraction thickness ranging between 9 and 14 feet. These values are based <br />on subsidence measurements at West Elk Mine (Table 1, Figure 5). The overburden depth above <br />the longwall panel centers ranges from 600 to 1,500 feet (Table 2).