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iiiiiuiiiiiiiiiiii <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman 51., Roam 215 <br />Denver, Colorado 80203 <br />Phone: (3031 R66-3567 <br />FA%: (303) 832-8106 <br />DATE: October 8, 1997 <br />TO: Mike Boulay <br />FROM: Jim Pendleton <br />RE: West E oat Mine R 225 -Water Tank Topsoil Stock Pile - <br />Geot hnica emenlal Submittal (Permit No: C-80-007) <br />I~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Roy Rnmer <br />Gnvemor <br />lames 5. Lnchhead <br />Enecaln'e Drzeclor <br />Michael B Long <br />Division Direcmr <br />I reviewed the stability analysis prepared by WESTEC, Inc., geotechnical consultant to Mountain <br />Coal Company (MCC). MCC submitted this analysis in response to my original incompleteness <br />opinion regarding their MR 225 application. You will recall that I recommended that their <br />application be deemed incomplete. because it lacked stability analysis for the proposed <br />excavation and loading of the foundational slope. <br />WESTEC completed a mathematical analysis of the proposed excavation and stockpile using <br />previously derived material properties for the foundational material and topsoil to be placed <br />within the stock pile. The assumed properties appear conservative and appropriate. The <br />computer analysis projects a static slope safety factor of 2.5 for the proposed stock pile. The <br />analysis has been completed following acceptable methodology. <br />I recommend approval of MR 225 with the following condition. Following excavation of the <br />foundational area to create the recommended 40 foot wide bench, MCC should install site line <br />slope stability monitoring monuments to provide visual indication of any slope movement within <br />the excavated footprint for the stock pile. As topsoil is placed within the stock pile, additional <br />site lines should be placed on the topsoil to indicate any instability within the stock piled <br />materials. MCC should also continue [o monitor the monument adjacent to the existing water <br />tank. <br />cc: Dave Berry <br />doc: M:\COALUAP\MTGMR225.WPD <br />]P/jP <br />