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-4- <br />• No substantial amounts of. ground water were encountered in the explora- <br />tory borings reported by Golder Associates in April 1977. To cover con- <br />ceivable conditions, a series of five water tables were used in this analysis. <br />The conditions studied represent water daylighting at elevations of l0, 50, <br />100, and 150 feet above the toe of the slope. Because of the method of spoil <br />pile construction, there is a possibility water could become perched on one <br />of the benches where heavy traffic may have compacted the spoil resulting in <br />lower permeabilities. We have assumed a condition fora perched water table <br />approximately 10 feet in thickness at the 6800 foot level. Water table con- <br />ditions are illustrated on Figs. 3 and 10. Field observation of spoil place- <br />ment indicates the material segregates itself into large cobble and boulder <br />sized material at the toe of each lift. This natural segregation creates a <br />. highly .permeable zone at the bottom, which essentially precludes the develop- <br />ment of a high water table condition. In our opinion, water table No. 4 and <br />a perched water table (No. 5) represent the most probable water table condi- <br />tions which could be encountered. <br />ANALYSIS TECHNIQUES <br />The stability of the proposed slope was evaluated using four methods of <br />analysis. Three of these analysis methods are applicable to circular failure <br />surfaces and include the graphical Swedish method of slices, the modified <br />Bishop, and the Spencer's methods. Block type failure modes were analyzed <br />using static summation of forces in the horizontal direction. <br />Both the Swedish and Modified Bishop analysis techniques analyze the <br />slope based upon a summation of forces for individual slices. These techniques <br />• are considered "approximate", since they do not account for interslice forces <br />