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Memorandum to Henry Barbe <br />September 27, 2000 <br />Page 5 <br />r • Henry Barbe, Environmental Engineer for MCC, reports that the cracks may have <br />developed on April 18, 2000, at about 5:30 p.m., when mine personnel felt an earth <br />tremor. Longwall mining in panel 12 was completed on March 8, 1999, according to a <br />MCC Mine Map. <br />• The larger cracks are straight to crenulate and diverging. The cracks are as much as 3%: <br />inches wide, more than 25 feet deep, 150 feet long, and are spaced from about 1 foot to <br />65 feet apart. Trend is N65-75°E, locally diverging to N40°E and N80°W to E-W. Some <br />of the lazger cracks located in the southern part of Apache Rocks are located above the <br />un-mined coal east of panel 12, the tail-gate entries of panel 13, and within the area of <br />influence of mined-out panel 13. Therefore, all these cracks are located within the <br />tension zone produced by the combined mining of longwall panels 12 and 13. <br />• The smaller cracks are as much as I inch wide, about 75 feet long, and aze more crenulate <br />' and diverging, but generally trend N40-50°W and N10-20°W. <br /> <br />1 <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br />Figure I <br />Eastward view of subsidexce cracks at Apache .Rocks. West Flatiron is in left <br />background. Cracks are located ix the tension zo,ve above the eastern boundary of <br />[ongwa(! panel 11. Cracks, which are as much as 3.5 inches wide, trend west- <br />norlhwestand cover an area 310 jeer in the north-south directon and I50-200 feet in <br />the east-west direction. <br />Wright Water Engineers, Inc., 2490 W. 26'" Avenue, Ste. 100A, Denver, CO 80211 <br />Tel. 303/480-1700; Fax. 303/480.1020, e-mail:knvright@wrightwater.com <br /> <br />