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West Elk Mine <br />• The following range of vertical displacements (subsidence values) are projected for the South of <br />Divide mining area based on the baseline data obtained from subsidence measurements above the <br />1NW, 2NW, and 3NW longwall panels at West Elk Mine (see Figure 3 and Table 1, Exhibit <br />60B) and the proposed E Seam mining configuration (Map 51). The projected range of maximum <br />vertical displacements, for the South of Divide mining area is shown in Table 2 of Exhibit 60B. <br />Overburden depth to the E Seam above the projected longwall centers within the South of Divide <br />mining area ranges from 400 to 1,425 feet. With a projected longwall panel width of 1,080 feet, <br />and assuming that the chain pillars (gate road pillars) are similar to those in longwall Panel 17 of <br />the Apache Rocks Mining Area, maximum subsidence (vertical displacement Sm =at) is <br />predicted as follows (Table 2 of Exhibit 60B): <br />• Panels EI to E8. These panels, which will trend roughly N80°W, will range in width from <br />subcritical to supercritical (width-to depth ratio (W/d) ranges from 0.76 to 2.7). <br />1. Maximum vertical displacement above the chain pillazs (Scp) is expected to range <br />from 0.8 to 2.4 feet (0.1 to 0.3t) where the extraction thickness is 8 feet, 1.2 to 3.6 <br />feet (0.1 to 0.3t), where the extraction thickness is 12 feet, and from 1.4 to 4.2 feet <br />(0.1 to 0.3t), where the extraction thickness is 14 feet. <br />2. Maximum vertical displacement (subsidence, Sm =at) is projected to range from 4.8 to <br />6.4 feet (0.6 to 0.8t) where the extraction thickness is 8 feet, from 7.2 to 9.6 feet, <br />where the extraction thickness is 12 feet, and from 8.4 to 11.2 feet (0.6 to 0.8t), where <br />• the extraction thickness is 14 feet. <br />• Panel E9. This panel trends about N10°E and is of supercritical width. <br />1. Maximum vertical displacement above the chain pillazs in this shallow overburden is <br />expected to range from 1.2 feet (O.lt), where the extraction thickness is 12 feet and <br />from 1.4 feet (O.lt), where the extraction thickness is 14 feet. <br />2. Maximum subsidence is projected to range from 8.4 to 9.6 feet (0.7 to 0.8t), where <br />extraction thickness is 12 feet, and 9.8 to 11.2 feet (0.7 to 0.8t), where the extraction <br />thickness is 14 feet. <br />Maximum Tilt <br />Maximum tilt (M,n) 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 />(S,n/d in dimensionless units L/L). Tilt values at West Ells Mine range from 0.014 to 0.021 <br />dimensionless units (L/L). Maximum tilt in four different mining azeas of the Western United <br />States ranges from 2.5 to 5 (S n,/d). <br />Apache Rocks Mining Area -Based on analysis of the current West Elk Mine subsidence <br />monitoring network, and using an average value of 2.7 (S,„/d), tilt above the eastern panels is <br />projected to range from about 0.006 in the southern flank of West Flatiron to about 0.027 near the <br />head of Sylvester Gulch. <br />1.05-129 Revised June 2005 PR70, Rev. Mach 2006; May 2006 PRI G <br />