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<br />III IIIIIIIIIIIII III <br />STATE OF COLORADO RiC HARD D. l/MM. Govan nr 9JJ <br />DEPARTMENT OF NATURAL RESOURCES <br />D. Monte Pascoe, Executive Direc[or <br />MINED LAND RECLAMATION <br />423 Centennial Building, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (30~) 866-3567 <br />David C. Shelton <br />Director <br />DATE: September 28, _'982 <br />~t7: Mike Long <br />c%_ _~ Q_- <br />FROM: Jim Pendleton ~~.;, .~.<. <br />RE: Reclaimed High I1 S bility Analyses - King Coal Mine <br />Pursuant to your request, 2 have reviewed the "Geotechnical and Stability <br />Analysis, Proposed Backfill Configurations, King Coal Mine, La Plata County, <br />Colorado (M,L.R.B. Stipulation)". This document, prepared by Fred M. Johnson, <br />consulting geologist to National King Coal Company, was submitted in <br />compliance with Stipulation No. 2 of King Coal Mine's permit No. C-035-8Z. <br />Mr. Johnson presents the results of a thorough geotechnical investigation <br />and reconnaissance geological mapping of the facilities area at the Xing <br />Coal mine. Xis investigation determined that~•.the,bedroek orientation~~af both <br />highwalls under consideration dips into the cut slope. In addition, no <br />detrimental faulting or fracturing occurs within the exposed highwall <br />faces. Both of these factors tend to increase stability of the cut slopes. <br />Further, Mr, Johnson analyzed the future stability of the proposed backfilled <br />configurations for both cut slopes, as required by Stipulation No. 2 of <br />the permit. The technique utilized by Mr. Johnson in completing the <br />mathematical analyses of these slopes is a rudimentary one. In addition, <br />several of his assumptions are debatable, such as angle of internal friction <br />equivalent to angle of repose for the cut face. For these reasons, I have <br />recomputed the safety factors utilizing rather broad ranges for these affected <br />variables. The results of my sensitivity manipulation has determined that <br />the slopes are within required conservancy even under some of the most <br />conservative strength assumptions. For this reason, I recommend that we <br />consider National King Coal Company as having complied with the requirements <br />of Stipulation No. 2 of their permanent program permit No. C-035-81. <br />/ep <br />cc: Ed Bisclnff <br /> <br />