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Y • The slice analysis was very thorough in locating the lowest factor of safety x and y coordinates for both the point of probable failure and the failure plane/surface. The analysis also included a condition "under seepage", indicating a worst case scenario if indeed the ditch should breach or be removed from the site. Under seepage the pile would still obtain the required factor of safety at 1.773 and be within compliance. I therefore support the report's recommendation that the ditch remain in place as a surface water diversion mechanism to establish the greatest possible stability of the rock fill. Some assumptions made in the analysis need to noted and are the following: 1. Derivation of the internal friction angle (Phi). o The internal friction angle is averaged to 41 degrees, which may or may not be the case. Direct shear analysis and proctor testing on the sampled SW-SM soil (a silty sand), indicated a Phi of 37 degrees. However, the silty sand material comprised only 46$ of the material sampled when passed through the No.4 sieve. Therefore, the key assumption is that a greater Phi is justified since 54$ of the material size was greater than sieve No.4. The relationship between particle size and Phi is a direct one, as particle size increases, so does the angle of friction. o The analysis proposes a Phi of 41 degrees. Using Dr. Huang's table,( pg 114); it is difficult to perceive how a Phi of 41 degrees was derived. If the remaining 54$ of the material was classified as GM then a Phi 34 degrees or greater is mentioned, but as to how much greater is not defined. Already in the SW-SM soil sample, a Phi of 37 degrees has been obtained. If we proceed up the chart to GP and GW classification, a Phi of greater than 37 or 38 is obtained, but again no mention of the upper limit. o It is a fact, that the higher the Phi, the higher the effective shear strength would be, therefore it is in the benefit of the research to choose the highest number for a Phi value as is possible and thus increase the factor of safety. I question the approach made by this research to "pick and choose" an upper limit. The Phi value of 41 degrees may be within reason, but should be clarified as to its derivation.