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2004 Geologic Hazard Field Observations <br />South of Divide Mining Area <br />• 7.1.1 Maximum Vertical Displacement <br />South of Divide Mining Area: The overburden depth to the E Seam above the projected <br />longwall centers ranges from about 400 to 1,425 feet. With a projected panel width of 1,080 feet, <br />and assuming that the gate road pillazs (chain pillars) are similaz 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 1): <br />• Panels El to E8: These panels trend roughly N80°W, and aze projected to range in width <br />from subcritical (see Exhibit 60B for definition of symbols) to supercritical (width-to-depth <br />ratio (4V/d) ranges from 0.76 to 2.7). <br />1. Maximum vertical displacement above the chain pillazs (S~) is estimated to range from <br />0.8 to 2.4 feet (0.1 to 0.3t) where the extraction thickness is 8 feet, 1.2 to 3.6 feet, where <br />the extraction thickness is 12 feet, and from 1.4 to 4.2 feet, where the extraction thickness <br />is 14 feet. <br />2. Maximum vertical displacement (subsidence, Sm at) is projected to range from 4.8 and <br />6.4 feet (0.6 to 0.8t) where the extraction thickness is 8 feet, from 7.2 to 9.6 feet, where <br />the extraction thickness is 12 feet, and from 8.4 to 11.2 feet, where the extraction <br />thickness is 14 feet. Maximum vertical displacement (11.2 feet) is projected to occur <br />within the azea of mining influence above the western limit of longwall panels E2 and E3 <br />should 14 feet of coal be extracted. <br />• Panel E9; This panel trends about N 10°E and is of supercritical width. <br />1. Maximum vertical displacement above the chain pillazs is projected to vary from 1.2 feet <br />(O.lt), where the extraction thickness is 12 feet and from 1.4 feet, where the extraction <br />thickness is 14 feet. <br />2. Maximum subsidence is projected to vary 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, where extraction thickness is 14 feet. <br />• <br />831-032.621 Wright Water Engineers, Inc. Page 13 <br />November 2004 <br />