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:~ <br />iii iiiiiiiiiiiuiii <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depanmenl of Natural Resources <br />1717 Sherman SI . Room 215 <br />Denver, Colorado 80203 <br />Vhone:1303)8h6-7567 <br />FA%:(3031832-BIOG <br />DATE: August 30, 1995 <br />TO: Barbara Pavlik <br />FROM: Jim Pendleton - <br />RE: Technical R TR- - <br />Coal Ridge N Mine <br />~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />~ Roy Romer <br />Governor <br />n1iV~ lames 5 Lochhead <br />L`C-31\~/.'(Vl^ Executive Dueuor <br />1cv Michael B. Long <br />- Division Director <br />Geotechnical Adequacy <br />(Permit: C-84-065) <br />I have reviewed the materials which you forwarded to me regarding <br />the above referenced technical revision application for the Coal <br />Ridge No. 1 Mine. I apologize for my Summitville related <br />tardiness. This technical revision was proposed to resolve several <br />inadequacies noted on a bond release inspection of the site. <br />Dozer Cut <br />A minor (15 foot wide) terrace crest outslope rotational slump <br />occurred this spring. Both the applicant and the Division agree, <br />based upon field observations, that the failure was precipitated by <br />water ponded adjacent to the outslope crest. This drainage <br />inadequacy resulted in saturation of the outslope face. The <br />applicant proposes to doze a notch and earthen ramp in the outslope <br />crest. This will lower the slope and provide a drainage course for <br />any surface water which might accumulate in the future. This ramp <br />will attain a slope angle significantly lower than the stable <br />outslope face immediately adjacent. Further, the additional <br />grading activity will excavate and recompact the failed material. <br />In addition the grading will eliminate the possibility of <br />resaturation. Therefore, I concur with Mr. Stover's opinion, and <br />conclude that the proposed regrading should result in a stable <br />configuration of the terrace outslope. In my opinion, the minimal <br />extent does not warrant a more sophisticated analysis. <br />Hackfilled Cutalope Above Stockpile <br />The Division also requested that the cutslope above the proposed <br />coal stockpile area be partially backfilled to lower the slope <br />angle of the cutslope. Material from the topsoil stockpile area <br />will be placed as a buttress adjacent to the lower third of the <br />existing cutslope. The final buttress facial slope will be finish <br />graded at a 3h:ly gradient. Because this slope is gentler than <br />