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-24- <br />• <br />After a number of trials it was determined that the most critical <br />condition existed when the spoil failed along the thin layer of <br />clay soils between the bedrock and the spoil pile. The minimum <br />factor of safety computed using dry conditions was 1.82. After the <br />factor of safety at dry conditions was calculated, various phreatic <br />surfaces were assumed to occur through the spoil pile. These <br />phreatic surfaces were input into the computer at a level elevation <br />corresponding to the elevation listed on the Summary of Stability <br />Analysis on Fig. 12. With the water surface at elevation 7310, <br />which assumes full saturation more than 100 feet above the toe of <br />the fill, the computed factor of safety was 1.37. If the water sur- <br />face was assumed at elevation 7410 which is near the top of the fill, <br />• the safety factor was still slightly above 1. These are saturation <br />conditions that are very unlikely to occur. Likelihood of satura- <br />tion is low because of the drainage which is planned to be in- <br />stalled in these fills as well as relative pervious nature of the <br />fill. The analysis of the stability of spoil configuration II-B is <br />presented on Fig. 13. Based on the results of our analysis of Spoil <br />Pile II-A we assumed that the critical failure surfaces would also <br />occur along the interface between the fill and the natural soils for <br />the analysis of Spoil Pile II-B. For Spoil Pile II-B, the lower <br />portions of the fill will be similar in performance to the analysis <br />shown for Spoil Pile I. The upper fill could fail by sliding along <br />the bedrock surface. The stability of this fill was investigated <br />• using 5 different failure surfaces, as indicated on Fig. 13. For <br />the conditions indicated on Fig. 13, the lowest computed factor of <br />