Laserfiche WebLink
• Mr. Jeffrey Dubber[, Blue Mountain Energy Inc., Deserado Mine <br />Slope Stability Calculations Coal Refuse Area # 2, #3 & #4, Deserado Mine, Colorado <br />lone 23, 2004 Page 3 <br />Calculated Factors of Safety (FOS) <br />110' Original Pile Height wF1:4 to 1:5 Face Slone <br />• <br /> <br />Refuse Pile Description Static FOS Pseudo Static FOS. <br />50' Added, 1:3 (v:h) 2.137 1.812 <br />75' Added, 1:3 (v:h) 2.116 1.796 <br />100' Added, 1:3 (v:h) {figure I} 2.100 1.784 <br />100' Added, 1:3 (v:h) 60' benches {figure II} 2.179 1.842 <br />100' Added, 1:3 (v:h) 75' benches {figure IIl} 2.174 1.825 <br />The computer modeling is consistent with previous Lincoln DeVore and Grand Junction Lincoln DeVore <br />studies in that the underlying bedrock model is the limitation on these slopes. The actual Coal Refuse is <br />stable at slopes as steep as 1=2.5, but the poorly defined `bedrock' (clay), with a potetrtial free water at the <br />toe azea, results in a large `Global' type failure. Better definition of the waterlmoisture conditions`in the <br />toe and bedrock area, with better bedrock strength data, is required for slope modiScations whiclrare <br />greater than those recommended in this report. <br />The Recommended Maximum Final Refuse Slope Configuration is shown in the larger picture, oii Figure <br />IV. The slope is benched and individual slopes aze 1:3 (vertical:horiwntal). The benches aze about 10' <br />wide, for future equipme~ mobilization, if required. The benches-aze spaced a maximum of 75' vertical, <br />and may start at any height less than 75' above the toe. The finaLslope configuration is:to be made based <br />upon expected slope erosion rates and storm water runoff criteria. This design process is a basic Storm <br />Hydrology problem, considering the runoff and sediment control. The 60' vertical dimension shown in <br />figure II is based upon our experience and our extrapolation from other coal refuse sites in the Western <br />Colorado azea. These areas experience more rainfall than the Deserado Mine and the Rangely Area. <br />It is believed that all pertinent points have been addressed. If arty further questions arise regarding this project <br />or if we can be of any further assistance, please do not hesitate to contact this office at atry time. ,' <br />Respectfully Submitted, <br />GRAND NNCTION <br />LINCOLN DeVORE, Inc. <br />by: Edward M. Morris PE <br />Principal Engineer <br />GJLD Job No.: 90875-GJ <br />30590 <br />