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~~ ._ <br />III III III IIIIIII III <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depanmeni of Natural Resources <br />IJ13 Sherman St.. Room 215 <br />Denver, Colorado 80203 <br />Phone: 13031 856-3557 <br />FA%: (3031 832-8 1 OG <br />DATE: January 10, 1997 <br />TO: Dan Mathews <br />FROM: Jim Pendleton <br />II~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />lames S Loch head <br />Executive Director <br />Michael B. Long <br />Division Director <br />RE: Munger Cany Mi - Haul Road Recl. Revision <br />Slope Stabi Analysis - Supplemental <br />(Permit No: C-80-020) <br />I have reviewed the supplemental submittal regarding the Munger <br />Canyon Mine's revised haul road reclamation plan and accompanying <br />slope stability analyses submitted by Grand Valley Coal Company <br />(GVCC), which you forwarded to my attention. <br />The proposed reclamation plan is a straight forward backfilling <br />plan. The haul road and mine bench are to be backfilled with on <br />site materials, compacted in lifts and graded to blend with <br />surrounding topography. Culverts are to be removed and drainages <br />returned to natural gradients. Some riprap will be installed to <br />help stabilize impacted reaches of drainages. Coal refuse from the <br />Fruita loadout will be used to partially backfill the mine portal <br />bench. <br />In support of the proposed reclamation plan, a computerized slope <br />stability analysis was performed of five representative cross <br />sections, three along the haul road and two on the mine portal <br />bench. In each case the REAME analytical computer program, <br />developed by the University of Kentucky, was used to analyze the <br />stability of the existing excavated section, the proposed <br />backfilled configuration, and the fill wedge. Material shear <br />strength parameters (cohesion, angle of internal friction, and <br />density) were assigned to the two soil materials encountered on the <br />haul road slopes, as well as to the general backfill to be used in <br />reclaiming the mine portal bench. No laboratory data or other <br />source was originally provided for the development of these <br />material strength parameters. In response to my adequacy request, <br />John Walters provided the references for the material strengths <br />used in completing the stability analyses. The material properties <br />were determined through laboratory testing by Geo-Hydro Consultants <br />while completing the approved road upgrade design, which was never <br />implemented. <br />