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~ . . <br />UU'ANIWENI Uh tt ATI1It«I Ill buUN(:.ES <br />Ilan rs D. $ncr m.u,. E„~~~r ~.vr U„~a tm <br />!11L'\h~U L,:~\II lih;la.:1~1:1'I'lO\ <br />723 Ce ntenn~al Budding, 1313 Sherman Street <br />Denvc r. Colorado 80203 Tcl. (3031 8923567 <br />Hamlet J. Barry, III, <br />Director <br />May 22, 1980 <br />TO: Rick M.i11s f/~ 1 <br />FROP1: Jim Pendleton ~„ / ~ ~. <br />RE: Yampa Coal's xcess Spoil Pile <br />~....--~ <br />As we observed at the site Wednesday, May 19th, 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 4:1. <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 Zies 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 ca pable 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 />Yregulations, the end-dumping technique of material placement will be. <br />disallowed, unless an experimental practice permit is obtained from Yampa <br />CoeI: <br />