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• <br />-23- <br />of the stability of the slope with a 100-foot wide buttress fill <br />at the toe of the slope. The lowest factor of safety for the 100- <br />foot wide key was 1.70. Figure 6 presents the computed factors of <br />safety for various combinations of failure surfaces and 200-foot <br />wide key. Figure 7 presents a summary of computed factors of <br />safety for the assumed failure surfaces with a 300-foot wide key. <br />Figure 8 shows the relationship between the width of the key and the <br />factor of safety. The factor of safety increases with increasing <br />widths of key. Failure surface No. 1 appears to be the most criti- <br />cal failure surface. A computed factor of safety of 2 was obtained <br />using the 200-foot width buttress fill and failure surface No. 1. <br />• In our opinion, this represents the most critical condition at <br />Spoil Area No. 1. Intermediate slopes exhibit high factors of safety <br />as indicated by the summaries on Figs. 1 <br />analyses are based on an unconsolidated, <br />in the clay layer immediately underlying <br />this will be the most critical condition <br />after construction before the clay layer <br />and gain strength. <br />S and 15. A11 of these <br />undrained, shear strength <br />the fill. In our opinion, <br />and will occur immediately <br />has a chance to consolidate <br />Two configurations were analyzed in Area II. The configurations <br />were identified as Configuration II-A and II-B. The base fill for <br />spoil pile Configuration II-B will be very similar to the conditions <br />in disposal I. We recommend that the base fill for Spoil Pile II-B <br /> be considered to be the same as design conditions at Spoil Pile Area <br />• I. For Spoil Section II-A various surfaces of failure were analyzed. <br />