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Evaluation of Bear No. 3 Mine Landslide <br />Rocky Mountain Geotechnical report. The findings of this block glide analysis are consistent <br />with earlier Rocky Mountain Geotechnical studies in ]986 which indicate adeep-seated failure <br />scenarios in the bedrock have relatively high calculated factors of safety. <br />The results of the previous geotechnical engineering analyses conducted in the vicinity of Beaz <br />No. 3 Mine can be summarized as follows: <br />• Stability analyses utilizing laboratory shear strength data from the site indicate shallow <br />translational failures near the bedrock colluvial contact are the most likely failure <br />mechanism. <br />• Hydrostatic pressures assumed to be acting on both the gliding block and the shallow <br />translational failures had a relatively small effect on the overall factor of safety obtained <br />in the stability analyses. <br />Figure 8 presents a plan and cross section view of the subject slide based on available <br />topographic information and field measurements. The cross section depicts an upper section of <br />the slide which has translated downslope resulting in a dilated and over-steepened middle section <br />of the hillside which was measured at 50° from the horizontal during our field visit. This over- <br />steepened section of the slope is metastable and continues to ravel releasing rock fragments <br />which roll to the toe of the slope. <br />Figure 8 also contains a plot of factor of safety against slope angle from a translational slope with <br />no seepage. This plot was developed from data in the 1982 Rocky Mountain Geotechnical report <br />on the nearby colluvial slopes on Sections A and D in the vicinity of the Bear No. 3 portal. Two <br />curves are presented on the plot. One represents peak sheaz strengths and the second residual <br />shear strengths. Based on the available topography, we estimated the slope angle to be about 39° <br />prior to the most recent landslide movement. Superimposing this original angle on the plot <br />results in factors of safety of less than one for the upper section of the hill at the landslide <br />location. <br />831-032.411 Wright Water Engineers, Inc. Page 11 <br />