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Subsidence Evaluation for the <br />Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 14 <br /> <br />831-032.923 Wright Water Engineers, Inc. <br />December 2021 <br />to 0.8t) where the extraction thickness is 14 feet. This estimate is only for the areas <br />over panels E2 to E5 and B26 to B29. <br />Apache Rocks West Mining Area: Overburden depth above the projected E-seam longwall centers <br />ranges from 400 to 1,100 feet. With a projected longwall panel width of approximately 1,080 feet, <br />maximum subsidence (vertical displacement Sm = a • t) is predicted as follows (Table 3) for the <br />Apache Rocks West mining area of panels E10 to E12: <br />• Panels E10 to E12: These panels range in width from subcritical to supercritical (width-to <br />depth ratio (W/d) ranges from 0.98 to 2.70). <br />1. Maximum vertical displacement above the chain pillars (Scp) is expected to range <br />from 1.0 to 4.0 feet (0.1 to 0.3t) where the extraction thickness is 10 feet, and 1.4 <br />to 5.6 feet (0.1 to 0.3t), where the extraction thickness is 14 feet. <br />2. Maximum vertical displacement above the mined longwall panels (subsidence, Sm <br />= a • t) is projected to range from 6.0 to 8.0 feet (0.6 to 0.8t) where the extraction <br />thickness is 10 feet, and from 8.4 to 11.2 feet where the extraction thickness is 14 <br />feet. <br />Overburden depth above the B-seam longwall centers ranges from approximately 750 to 1,300 <br />feet. With a longwall panel width of 950 feet, maximum subsidence (vertical displacement Sm = a <br />• t) is predicted as follows (Table 3) for the Apache Rocks West mining area of panels B12 to <br />B13A: <br />• Panels B12 to B13A: These panels range in width from subcritical to supercritical (width- <br />to depth ratio (W/d) ranges from 0.73 to 1.27). <br />1. Maximum vertical displacement above the chain pillars (Scp) is expected to range <br />from 1.2 to 4.8 feet (0.1 to 0.3t) where the extraction thickness is 12 feet. <br />2. Maximum vertical displacement above the mined longwall panels (subsidence, Sm= <br />a • t) is projected to range from 7.2 to 9.6 feet (0.6 to 0.8t) where the extraction <br />thickness is 12 feet. <br />The E-seam panels E10 to E12 and B-seam panels B12 to B13-A occur on top of one another, but <br />are not stacked based on the current panel layout (Figure 1). However, to be conservative, the <br />maximum subsidence (vertical displacement Sm = a • t) of the two seams is assumed to be additive. <br />3. Maximum vertical displacement above the chain pillars (Scp) due to both E-seam <br />and B-seam mining cannot be estimated, as the chain pillars for the E-seam and B- <br />seam are not located on top of one another. <br />4. Maximum vertical displacement above the mined longwall panels (subsidence, Sm= <br />a • t) for the B-seam and E-seam mining is projected to range from 13.2 to 17.6 feet <br />(0.6 to 0.8t) where the E-seam extraction thickness is 10 feet, and from 15.6 to 20.8 <br />feet (0.6 to 0.8t) where the E-seam extraction thickness is 14 feet. This estimate is <br />only for the areas over panels E10 to E-12 and B12 to B13-A. Due to the offset