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West Elk Mine <br />• completed, is projected to range from 0.00026 to 0.00132 rad/ft. Maximum negative curvature <br />projected in the westem panels for E and B-Seam mining ranges from approximately -0.00026 to <br />-0.00132 rad/ft. <br />Box Canyon Mining Area -Maximum positive curvature for the two northern panels, Panels 1 and <br />2, is projected to be 0.000030 to 0.000410 rad/ft; for Panel 3, 0.000024 to 0.000202 rad/ft; for <br />Panels 4 through 6, 0.000016 to 0.000239 rad/ft. Similarly, maximum negative curvature is <br />projected at -0.000022 to -0.000410 rad/R for Panels 1 and 2; -0.000024 to -0.000202 rad/ft for <br />Pane13; -0.000016 to -0.000239 rad/ft for Panels 4 through 6. <br />Maximum Horizontal Strain <br />Maximum positive horizontal strain (Em) measured in the West Elk Mine monitoring network <br />ranges from 1.1 to 1.4 (Sm/d) (0.0058 to 0.0102, that is 0.58 and 1.0 percent); maximum negative <br />strain between -0.20 and -4.0 times (Sm/d) (or 0.0009 and 0.0307, that is 0.09 to 3.0 percent) <br />(Table 1 of Exhibit 60B). The range of horizontal tensile strain in four different mine areas of <br />the Western United States studied by Mr. Dunrud is 0.45 to 3 (Sm/d). <br />Maximum tensile and compressive strain is significantly greater above large barrier pillazs and <br />rigid chain pillars and mine boundaries than it is above longwall mining faces. This is because <br />tensile strains caused by mining the two adjacent panels aze additive above the common rigid <br />chain pillars or unyielding mine panel boundary pillars. Cracks tend to be wider and deeper <br />above barrier pillazs or lease boundary bamer pillars than chain pillazs because of their greater <br />. rigidity (for example, the large tension crack on the north side of Lone Pine Gulch). <br />The tensile strains presented in Exhibit 60B (Figure 4) aze believed to be conservative for the <br />South of Divide mining azea. Maximum horizontal tensile strains, measured by Mr. Dunrud in <br />bedrock during annual observations in the Apache Rocks azea (in hard brittle sandstone, where <br />the only strain is revealed by cracks), were 0.0031 to 0.0062 (0.31 to 0.62 percent). The tensile <br />strain is considered to be close to a maximum value for those observed by Mr. Dunrud in the <br />Apache rocks azea because (1) the features are located above the azea if influence of a large solid <br />coal pillaz and (2) no greater strain was observed in the Apache Rocks mining area. <br />Apache Rocks Mininn Area -The horizontal tensile strain in the eastern panels after B Seam <br />mining is projected to range from 0.003 on the south flank of West Flatiron (overburden depth is <br />about 2,250 feet) to 0.013 (units are dimensionless [L/L]) near the head of Sylvester Gulch. <br />Projected horizontal tensile strain for the western panels for E Seam mining are 0.008 above the <br />thickest overburden on the ridges to 0.023 above the thinnest overburden in Horse Gulch. Tensile <br />strain after both E and B Seam mining is completed may range from about 0.016 to 0.041 above <br />thickest and thinnest overburden, respectively. <br />Projected horizontal compressive strain will be in the panel centers. In the eastern panel area, using <br />an average value of 2.0 (Sm/d) from the West Elk Mine subsidence network, compressive strain is <br />projected to range from -0.004 near the south flank of West Flatiron to -0.020 neaz the head of <br />Sylvester Gulch. Compressive strain above the westem panels after E Seam mining is estimated to <br />• range from -0.013 in azeas of thickest overburden to -0.035 in azeas of thinnest overburden. After <br />2.05-13I Revised Jame 1005 PRIO, Rev. March 2006; May 1006 PRIO <br />