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File No. 20-1100-38 KLEIN F E L D E R September 12, 1996 SLOPE/W was also used to analyze multiple wedge slip surfaces and computed a critical failure surface. The actual slope configurations will be 1%:1 (1%: horizontal to 1 vertical), according to discussions with Teichert. Slopes with wedge, block, and circular slip surfaces were analyzed, as shown on Plates B-1 through B-8. A summary of all the loading conditions, slope configurations and soil profiles for the excavated slopes is shown on Plates B-1 through and B-8. A summary of computed factors of safety for all the slopes analyzed is presented in Table 2, below. We have attached all of our computer printouts to the end of this report in Appendix B. As noted, the Factors of Safety for the slopes varied from 1.3 to 3.8, with the lower values associated with seismic events. Based on observations of highway cuts, etc., in similar material, it is likely that a relatively flat slip surface would extend from the surface downward to a point of intersection on the slope or to point of inconsistent material, such as a seam of clay or clean sands, then outward to the exposed slope. This is reflected in the failure planes shown in Appendix B which generally have large radiuses over 200 feet. TABLE 2 Profile Profile Seismic Computed No. Type Coefficient Factor of Safety I Wedge/Block 0 3.8 1 Wedge/Block 0.15 1.6 1 Circular 0 1.7 1 Circular 0.15 1.3 2 Wedge/Block 0 3.2 2 Wedge/Block 0.15 3.0 2 Circular 0 2.4 2 Circular 0.15 1 2.0 s We caution that some minor sloughing and/or erosion of the slopes should be anticipated, particularly in the loose upper materials of the excavated slopes. We recommend that the portions of the excavated slopes in residual soils alluvial deposits be protected from erosion as soon as possible after construction. In addition, the flow of surface water over the slopes should be minimized by constructing channels to divert the flow away from the slopes. Typically, factors of safety on the order of 1.5 or greater are desired for embankments. Factors of Safety on the order of 1.1 or 1.2 or greater are desirable for seismic events. We note that we were also conservative in our selection of soil strength values. 20-1100-381MR960198 Page 5 of 01996, Kleinfelder, Inc.