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<br />r <br />DEP ART MEN7 OF N47URAL RESUUUC~ III III III IIIIIII III <br />Harns D. Snc,man. Exr cid ivr Uirerrnr~ 999 <br />AI 1~'~ EI ) L:1 \ I 1 I{ I~;(;L:1~1:1'I'I(1\ <br />723 Centennial 8uildin9, 1313 Sherman Sireet <br />Denver, Colorado 80203 Tel. (303) 692-3567 <br />Hamlet J. Barry, I I I, <br />Director <br />May 22, 1980 <br />TO. Rick Mills //~~ J <br />FROM: Jim Pendleton ~, / ~ ~'~~ <br />RE: Yampa Coal's xcess S~poi1 Pile <br />~._..-~ <br />As we observed at the site Wednesday, May 14th, the excess spoil pile <br />at Yampa Coal's strip pit requires some remedial treatment. The major <br />problem appears to be oversteepening of the outslopes of the spoil piles. <br />Small zones of tension cracking, indicative of slope instability, were <br />evident throughout the outer periphery along the top of the pile. One <br />major area of observed cracking and possible slope bulging was observed <br />on the "reclaimed"face of the pile facing their office area. While <br />the company's representatives insisted that the angle of slope ranged <br />from 5:1 to 3:1 (horizontal to vertical) throughout this area, my <br />visual perception leads me to believe that actual slope angle was closer <br />to 2:1 to 9:1. <br />Unless the company is willing to submit an appropriate stability analysis <br />to verify the disposal pile's slope stability at steeper angles, I suggest <br />that you require reduction of the pile's slopes to an angle no greater than <br />3:1 throughout. Particular and immediate care should be required on that <br />portion of the northern face of the pile which lies above the undisturbed <br />mountain valley of the adjoining areas. I suggest that the topsoil <br />should be removed, the slope regraded to 3:1, the subsoils properly compacted, <br />the surface roughened, the topsoil reapplied, and the slope revegetated <br />as promptly as is practicable. Throughout the remaining areas of the excess <br />spoil pile's slope, final grading should be capable of achieving a more <br />stable slope configuration. Until that time, the marginally stable <br />conditions of the end-dumped spoil pile will probably constitute a major <br />operational inconvenience for the operator. 'Under the permanent proposed <br />'~reguIations, the end-dumping technique of material placement will be <br />disallowed, unless an experimental practice permit is obtained from Yampa <br />Coil <br />