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i --- - -- --�— — � KLEINPELDER Perched groundwater was encountered in our borings at depths ranging from about 82%2 to 110 feet below the existing ground surface. Our firm does not know the extent of the perched groundwater at this time. However,based on information provided by Don Pedro Drilling who services many wells in the area, including at the DSS and Teichert quarries, well soundings in the project area indicate that beneath the perched water encountered in this investigation groundwater is located at a depth greater than about 200 feet below the existing grade. 5. RECLAIMED SLOPES Based on our analysis presented in Section 6 and our previous laboratory tests, the reclaimed slopes should be compacted near the optimum moisture content to at least 85 percent relative compaction. We note that Kleinfelder previously performed a limited number of nuclear density gauge tests on reclaimed soils that had been compacted by loaded scrapers at Teichert's Vernalis Plant. Our tests indicated that the relative compaction of these soils was generally greater than 85 percent. 6. SLOPE STABILITY ANALYSIS The slope stability analyses were performed using SLOPE/W, a computer program from Geo- Slope International. The slope configuration is presented in the appendix. The soil properties used in our analyses are based on the results of the field and laboratory investigations performed for this study as well as those performed previously in the project area. Summarized in the table below are the soil properties for the four basic soils used in our analyses. - SOIL PROPERTIES Angle of Internal` Moist Unit Soil a Friction(degrees) Cohesion s Wei ht c I Cemented mixture of sand, 36 900 120 gravel, and cla II. Sandy clay 24 500 115 Weakly cemented silty sand 25 350 120 L Reclaimed soil 27 950 130 Based on our experience, slope failures in cemented soils, such as those soils encountered in the Vernalis area, tend to occur as block or wedge failures rather than deep circular failures. In other words, the likely slip surface would develop at the ground surface at the top of the slope and extend downward to a point of intersection on the face of the slope. To account for this mode of failure, various block slip surfaces were modeled to estimate the most likely failure planes as well as the minimum factors of safety. However, due to the high fines content and no r l 2900TGOUST03R1215 August 21,2003 0 2003 Kleinfelder,Inc. Page 3 of 5