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STATE OF COLORADO RiCHnRn D. Gove~~ai ~~~ ~~~ll~~j~l~lj1lj DEPARTMENT OF NATURAL RESOURCES Harris D. Sherman. Executive Director ggg MINED LAND RECLAMATION 723 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 8923567 May 22, 1980 TO: Rick Mi11s FROM: Jim Pendleton /// ~~ RE: Yampa Coal's cess it Pile •M Hamlet J. Barry, III, Director Rs we observed at the site Wednesday, May 14th, the excess spoil pile at Yampa Coal's strip pit requires some remedial treatment. The major problem appears to be oversteepening of the outslopes of the spoil piles. Sma11 zones of tension cracking, indicative of slope instability, were evident throughout the outer periphery along the top of the pile. One major area of observed cracking and possible slope bulging was observed on the "reclaimed"face of the pile facing their office area. While the company's representatives insisted that the angle of slope ranged from 5:1 to 3:1 (horizontal to vertical) throughout this area, my visual perception leads me to believe that actual slope angle was closer to 2:1 to 4:1. Unless the company is willing to submit an appropriate stability analysis to verify the disposal pile's slope stability at steeper angles, 2 suggest that you require reduction of the pile's slopes to an angle no greater than 3:1 throughout. Particular and immediate care should be required on that portion of the northern face of the pile which lies above the undisturbed mountain valley of the adjoining areas. I suggest that the topsoil should be removed, the slope regraded to 3:1, the subsoils properly compacted, the surface roughened, the topsoil reapplied, and the slope revegetated as promptly as is practicable. Throughout the remaining areas of the excess spoil pile's slope, final grading should be capable of achieving a more stable slope configuration. Until that time, the marginally stable conditions of the end-dumped spoil pile will probably constitute a major operational incronvenience for the operator. Under the permanent proposed regulations, the end-dumping technique of material placement will be disallowed, unless an experimental practice permit is obtained from Yampa Coal.