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III IIIIIIIIIIIIIIII DEPARTMENT OF NATURAL RESOURCES yy9 David H. Getehe4 Executive Director MINED LAND RECLAMATION DIVISION DAVID C.9HELTON, Dlnetor Richard D. Lamm Governor DATE: April 2, 1984 ~- T0: Dan Mathews I //1 FROM: Jim Pendleton ~ "°' '~ RE: Red Canyon MkYne S lotion 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. Backf111ing and Grading Stipulation Western Associates' consultant, Rocky Mountain Geotechntcal, Inc., prepared a stability analysis of alternative proposed portal bench and cut-face configurations and the final proposed reclaimed conflguratlon at the Red Canyon No. 2 Mine. The consultant completed afield mapping investigation and utilized material strength properties derived from prior geotechnical investigation efforts in the immediate area of the "D" seam portal. The analysis, prepared in accordance with the prudent state-of-the-art, determined a static slope safety factor 1n 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 backfilled final conflguratlon. The analysts has demonstrated the acceptability of the proposed portal cut face and bench fill configurations and satisfies the requirements of Stipulation No. 8. Subsidence MaDDtn9 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)(11)(C)-1. /cd cc: Brian Munson Doc. 0457E 423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (30:x) 866-3567