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III IIIIIIIIIIIII III <br />A 999 <br />~T1 1T L O F COLORADO <br />.. <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman 51.. Room Z1S <br />n_.,... _. w w~.~.3 <br />Phone! 0031 866 3 5 6: <br />FAX X303) 83?-8706 <br />May 28, 1993 <br />Mr. Mark Kerr <br />Landmark Reclamation Inc. <br />4901 South Windemere <br />Littleton, CO 80210 <br />pp cow <br />°:v <br />ti~ 4~~ <br />• ~. <br />~. ~ <br />• ~ rB]6 <br />Roy Romer <br />Governor <br />Michael B. Long <br />Division DneUar <br />RE: Stability Analysis, Rimrock Coal Company, Rimrock Strip Mine <br />Permit No. C-89-074, Cessation Order No. CO-93-054 <br />Dear Mr. Kerr: <br />On April 13, 1993, the Division issued Cessation Order No. CO-93-054 <br />for Rimrock Coal Company's failure to achieve sufficient compaction <br />of its sediment pond embankment to ensure stable embankment slopes <br />with a minimum safety factor of 1.3. The steps cited in the <br />Cessation Order necessary to abate the violation were for Rimrock <br />Coal Company to: <br />1. Reconstruct the embankment in compliance with Technical Revision <br />No. 1, Rule 4.05.6(11), and applicable requirements of <br />Rule 4.05.9(3) for embankments in excess of 10 feet in vertical <br />height. <br />2. Complete reconstruction and submit certification required by <br />Rule 4.05.6 and 4.05.9(13)(b) by April 13, 1993. -r~~ ~°~'""~~ <br />On May 14, 1993, the Division received from Greg Lewicki and <br />Associates a certified report stating that the sediment pond dam, as <br />measured from the bottom of the original ground surface to the bottom <br />of the emergency spillway, is 9.9 feet in height, and, as such, does <br />not meet the large impoundment criteria of Rule 4.05.9(3), the State <br />Engineer's office, or C.R.S. 37-87-105. <br />There is, however, an additional item to consider. Rule 4.05.6(11)(k) <br />states that sedimentation ponds not meeting the size or other <br />criteria of 30 CFR 77.216(x)(1989), and which are located where <br />failure would not be expected to cause loss of life or serious <br />property damage, shall have a minimum safety factor of 1.3 for a <br />normal pool with steady state seepage saturation conditions. <br />