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. `; <br />KLH Engineering <br />Slope Stability for Reclamation <br />O.C. Mine #2, Gunnison County, Colorado <br />September 25, 1995 Page 2 <br />cient. For this analysis, only a horizontal earthquake coeffi- <br />cient was utilized. <br />Results of the Stability Analysis are as follows: <br />Section Ultimate Strength Factor of Safety <br /> Pseudostatic <br />" A-A' ld=23.2 @ C=249 1.45 <br />B-B' Jd"=23.2 @ C=249 1.83 <br />C-C' ;P1=23.2 @ C=249 1.40 <br />D-D' Id=23.2 @ C=249 1.63* <br />The section D-D' was calculated using the complete slope, meas- <br />ured from the lower drainage ditch to the back side of the first <br />bench. In addition, a second analysis was performed removing the <br />small wedge of more recent mine waste, placed at the front edge <br />of the bench. The analysis above was taken after this small <br />wedge was removed and placed near the back, North portion of the <br />bench. During the original analysis, this small wedge was found <br />to have a safety factor of 1.27, if the soils were saturated, <br />which would probably occur during snowmelt. <br />Based upon our analysis, the existing slopes on the site appear <br />to be stable, with the exception of the small area of mine waste <br />on the first bench. It is recommended this wedge be removed. In <br />addition, the slopes immediately around and above the collapse <br />adit, on the second bench, are presently raveling. It is recom- <br />mended these slopes be reduced, for erosion purposes. A large <br />failure of these slopes, involving more than approximately 100 <br />cubic yards of material is not likely however, raveling of these <br />slopes is expected to continue if these slopes are not flattened. <br />It is recommended these slopes be filled at the toe areas, in <br />order to accomplish a maximum slope of 1.5:1 (horizontal:verti- <br />cal). <br />The slopes in this general area should be classified as poten- <br />tially unstable. In general, large slope failures are not antic- <br />ipated however, small failures and soil creep is possible. It is <br />strongly recommended that any reclamation work accomplished on <br />this site tend to flatten existing slopes and not undercut any <br />natural or man-made slopes. It is further recommended that all <br />drainage in the area be carefully controlled and water not be <br />allowed to accumulate or pond in any area. In addition, it is <br />strongly recommended the upper drainage ditch, placed above this <br />site at elevation 9327 to 9330 be allowed to remain as long as <br />