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J.E. Stover & Associates Terracon Project No. 65995058 June 3, 1999 The stability of the proposed cut slope on the transfer bench appears to be the most critical (i.e. lowest calculated factor of safety against slope instability). The stability analyses of this slope indicate that the potential failure surface with the least calculated factor of safety encompasses a significant amount of the natural slope above the proposed cut, and has a relatively deep seated potential failure surface. The presence of bedrock at the locations included in the stability model also affect the location and the factor of safety on the critical failure surface for this proposed slope. As previously discussed, the limiting boundaries were included in the cross section to simulate the presence of underlying bedrock. These boundary conditions were used to deflect all potential failure surfaces analyzed in an upward direction. Consequently, all failure surfaces analyzed for this cross section were contained within the soils lying above the estimated level of bedrock. DESIGN AND CONSTRUCTION CONSIDERATIONS Earthwork Considerations: The recommendations contained in this report for the proposed • construction are contingent upon compliance with the specifications for earthwork as outlined in the reports by both Lambert and Maxim for the project. Construction of earth fills should be in accordance with the specifications that are outlined in the geotechnical reports. Testing and documentation of the construction of the embankment should be performed to provide records that will be adequate to satisfy requirements of the applicable regulatory agencies. Cut Slope Construction: Our analyses regarding proposed cut slope stability assume the analytical models accurately depict the subsurface conditions along each cross section. The analyses also assume that the conditions are uniform in directions perpendicular to the cross- sections. Since the cut slopes will be made into ancient landslide materials, we anticipate that there will be some variability in the materials in the actual cut slopes. These conditions will not likely become evident until excavations proceed. Therefore, engineering evaluation of actual conditions encountered in each excavation are recommended during construction to confirm the consistency of materials and to determine the validity of the design models used in our analyses. Any deviations should be evaluated first hand so that the validity of the analytical models used for the stability evaluations can be confirmed or modified as necessary. The transfer bench is the structure where potential variability in subsurface condtions could negatively impact the performance of the final cut slope configuration and stability. Because of the relatively low calculated safety factor and the critical nature of this structure, consideration 9