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West Elk Mine <br />• South ofDivide Mining Area and Dry Fork Lease 7 <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 S,,, =at) is <br />predicted as follows (Table 2 of Exhibit 60B and 60E): <br />• Panels El 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 pillars (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, 5,,, =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 />a Panel E9. This panel trends about N10°E and is of supercritical width. <br />1. Maximum vertical displacement above the chain pillars in this shallow overburden is <br />expected to range from 1.2 feet (0.1t), where the extraction thickness is 12 feet and <br />from 1.4 feet (0.1 t), 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 />Maxim-urn tilt (M,,,) 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 />(5,,,/d in dimensionless units L/L). Tilt values at West Elk Mine range from 0.014 to 0.021 <br />dimensionless units (L/Q. Maximum tilt in four different miring areas of the Wester United <br />, <br />States ranges from 2.5 to 5 (S ,,,; u_; <br />?. <br />Apache Rocks 111ininge Area - Based on analysis of the current West Elk Mine subsidence <br />monitoring network, and using an average value of 2.7(5,,,/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 />2.06-129 Revised June 2005 PRIO, Rev..Vm-ch 2006; Alay 2006 PRIO. Nov. 2006TRIOT.4pril 2007TR708; Sep. 2007 PR12; Feb. 2008 PR-12