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DEPARTMENT OF NATURAL RESOURCES David H. Getches, Executive Director MINED LAND RECLAMATION DIVISION DAVID C. SHELTON, Director Richard D. Lamm Governor DATE: April 2, 1984 T0: Dan Mathews FROM: Jim Pendleton ~ RE: Red Canyon ne S a n on and Commitment Responses Pursuant to your request, I have reviewed the stipulation and commitment responses recently submitted by Grand Mesa Coal (Western Associates, Inc.) for their Red Canyon Mine. I forward the following comments for your consideration. Backfilltng and Grading Stipulation Western Associates' consultant, Rocky Mountain Geotechnical, Inc., prepared a stability analysis of alternative proposed portal bench and cut-face configurations and the final proposed reclaimed configuration at the Red Canyon No. 2 Mine. The consultant completed a field mapping investigation and utilized material strength properties derived from prior geotechnical investigation efforts in the immediate area of the "D" seam portal. The analysts, prepared in accordance with the prudent state-of-the-art, determined a static slope safety factor in excess of 2.04 for the steepest proposed 2:1 (horizontal to vertical slope) cut face slope, 1.52 for the worst case fill bench, and 2.42 for the proposed backftlled final configuration. The analysis has demonstrated the acceptability of the proposed portal cut face and bench fill configurations and satisfies the requirements of Stipulation No. 8. Subsidence Mapping Commitment The operator committed, within the amended permit application, to submit "safety zone" limited extraction delineations for the "D" seam, prior to mining within the "D" seam at the Red Canyon No. 2 Mine. The operator has satisfied this commitment with the submittal of an amended sheet 1 of 2 of map No. 2.05.6(6)(f)(1i)(C)-1. /cd cc: Brian Munson Doc. 0457E 423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567