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Memorandum to Christine Johnston <br />October 7, ]999 <br />Page 7 <br />1 <br />!.J <br />• The model for downwarping and flexure of differing rock types presented in Exhibit 60 of <br />the West Elk Mine Permit indicates that a zone of compression would occur below this <br />10-foot depth. <br />• The cracks trend N-S with only a 5 <br />degree variation, aze as much as l %Z <br />inches wide, and are locally offset <br />vertically by as much as '/< inch (Figure <br />5). Cracks cutting the sandstone aze <br />locally offset horizontally along planes of <br />weakness, but then maintain the N-S <br />trend. <br />• The cracks range in spacing from 5 ft to <br />50 ft near location and from 50 to 150 ft <br />either way from point along ridge. <br /> <br />e,. :~ <br />.,aA~!,,,, s~At <br />«. <br /> ,q,... ._. A: <br />~ ~• <br /> <br />~'; <br />.~~~ <br />r'' . 1~ <br />.' <br />~ ~ ~ <br />~ <br />HS .y a <br /> <br />,:,: w ~'10~ v .~ ' ~ , rk,? <br />. <br /> <br />~ i,.« ~ <br />i 5 <br />:.,~. <br />Yti , <br />. ,~ R, F .~ <br />Figure 5. Tension crack in sandstone that is offset <br />about I inch. Located in dynamic wne above <br />longvvall min ing Face in Panel 13. <br />• Two compression bulges, as much as 6 <br />inches high 4 ft long and wide, were <br />observed next to two different tension <br />cracks (Figure 6). <br />Location 7. Located at monitoring well SOM-16-H (F-Seam Well). <br />• Overburden depth to B-Seam is about 1,400 ft. <br />• Ron Hanna reports that the monitoring probe was obstructed at 840 ft during his visit on <br />' 7-20-99. The casing is apparently offset or kinked at this depth now. Before this, he was <br />able to record a water level at 1,000 ft depth, a level that remained relatively constant over <br />the last ten years. <br />' Wright Water Engineers, Inc., 2490 W. 26'" Avenue, Ste. 100A, Denier, CO 80211 <br />Tel. 303/480.1700; Fax. 303/480.1020, e-mail:krwright@wrightwater.com <br />