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<br />David Berry -24- June 20, 1996 <br />the now Bowie #1 mine (B1M). However, BRL <br />considers Panel #36 to be oriented perpendicular <br />longitudinally to the outcrop, unlike the lat West <br />Panel at B1M which is parallel. BRL also suggests <br />that the outcrop barrier pillar at B1M was not <br />properly designed, unlike the outcrop barrier <br />pillar at B2M. It is also worth pointing out that <br />adjacent to the area of significant subsidence <br />cracking, the 1st West Panel is 800' wide and <br />underlies an average 300' of overburden classifying <br />it as a super-critical panel (w/d > 1.4). The <br />predicted first west panel subsidence based on; 1) <br />the example in Exhibit 15; 2) 908 recovery; and 3) <br />a mining height of 14 feet is 6.8 feet. This is <br />over twice the maximum calculated subsidence for <br />the B2M. The predicted tensile strain and <br />compressive strain for the 1st West Panel are <br />15,000 and 13,000 u-in/in respectively, which are <br />50B greater than the maximum strains calculated for <br />the B2M. HRL would not consider these cases a <br />good comparison. <br />Paragraph 3: The DMG's analysis of the projected maximum <br />vertical subsidence for two points along the long <br />axial centerline of Panel 36 is incorrect for the <br />first point chosen, for the following reasons: <br />1) The DMG assumes that the pillars in panel #36 <br />will be fully extracted, neglecting any reduction <br />due to partially extracted room and pillar mining. <br />2) The DMG assumes that the face advance is limited <br />to less than about (1.4 times the overburden depth <br />at a point 0.7 times the overburden depth from the <br />panel end) 560', thus the use of figure 4 of the <br />$EH. Figure 4 would produce a limited advance <br />reduction factor of 0.93 rather than the 0.7 <br />determined by the DMG. <br />BRL would predict the maximum amount of subsidence <br />for this point, using the example shown in Exhibit <br />15 and taking into consideration the planned <br />configuration of panel #36 to be 2.8', slightly <br />less than 3.4' the maximum vertical subsidence <br />predicted by BRL and significantly smaller than <br />6.1' projected by the DMG. The point analyzed is <br />in the zone of greatest subsidence impact with an <br />overburden depth of 400' and the 2.8' is in the <br />range of subsidence magnitude predicted. <br />Paragraph 4: The second point chosen by the DMG for a SEH <br />subsidence projection is located at the center of <br />