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Memo to Dave Berry Bowie No. 2 Additional Geotech Study page 5 unless the rock mass is retained as excavated. I suspect that this same problem might be encountered to varying degree in other cuts throughout the site. These slope situations are currently buttressed by the soil and debris veneer of the large ancient landslide mass earlier identified by Maxim Technologies. The deep excavation of the proposed benches will first remove the soil buttress, potentially exposing meta-stable bedrock faces analogous to those evidencing instability in the undisturbed situation. Unless great care is exercised, these slopes will fail, potentially catastrophically, as a result of removal of the soil and landslide debris buttress. Further, they will be exposed to the disturbance of near outcrop portal penetration, operational vibration, hydrologic alterations, and exposure to increased temperature fluctuation. All of these factors commonly contribute to mechanical destabilization of a slope. For purposes of Maxim's analyses, the primary subject of this memorandum, the above concern implies a shortcoming in their analytical assumptions. The general analyses performed in this study assume that the bedrock is a uniform homogeneous material with strength properties significantly higher than that of the reclaimed soil wedge. The excavated bedrock bench is portrayed as a stable foundation into which the soil wedge is placed. In other words, the failure scenarios are effectively limited to the backfilled soil wedge. A "conventional circular stability analysis" is ideally suited for such an analysis. Unfortunately, I suspect that this basic assumption may be inappropriate in the situation presented by the Bowie #2 mine site. At this site it is more likely that the exposed bedrock is prone to failure along specific bedding planes and joint faces. The mechanical frictional properties of the rock mass in effect along these planes of weakness is significantly weaker than the properties of the intact rock matrix determined by triaxial testing of a minuscule rock specimen in a laboratory test cell. Further, analytical techniques designed for wedge-type failure mechanisms should be evaluated for comparative projections of potential bedrock instability scenarios.