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E l I KLIEINFELDER IV. SLOPE STABILITY ANALYSIS FOR SAND AND GRAVEL 1. eld Explorations The field explorations were performed on December 10 and 11, 1997, and consisted of drilling a total of five test borings. The locations of our borings are shown on Plate A-1 of Appendix A. The borings were drilled to depths of approximately 50 to 85 feet below the existing ground surface and generally encountered refusal due to cobbles. The borings were located by pacing in the field and were drilled with truck-mounted drill equipment using 8-inch diameter, hollow-stem I augers. Continuous logs of the materials encountered in the borings were maintained by an engineer from our firm who assisted in obtaining relatively undisturbed soil samples from the borings for visual f observation, classification, and laboratory testing. Attempts were made to recover relatively # undisturbed samples of the soils encountered primarily in those zones where tip resistance } indicated loose, fine-grained deposits. However, in most instances, it was not possible to recover i testable samples because of the gravelly or dense nature of the materials. lSoil samples were obtained by driving an approximate 2-inch, inside-diameter sampler into the soils using a 140-pound hanuner falling approximately 30 inches. The number of blows required to advance the sampler into the last 12 inches of soil is presented in the Logs of Borings, Appendix A, Plates A-4 through A-8 at the corresponding sample locations. After the borings were completed, they were backfilled with either the drill cuttings or "hole plug" in accordance with San Joaquin County of Public Health Services requirements. Z. Soil Conditions The surface soils encountered in our borings generally consisted of gravelly soils with ocmional cobbles and thin clay, silt, or sand lenses to the maximum depths explored. The borings drilled by Granite Construction Company also consisted of gravelly soils with interbedded lenses of sand, silts, and clays. { Based on the manner of drilling and our experience in the area, we conclude that the sand and I gravel deposits encountered in our borings are partially cemented. The silt and clay deposits encountered in the borings are most likely also partially cemented. We note that similar silt and i clay soils exposed in deep excavations adjacent to the site still show teeth marks left by excavating equipment years earlier. No fi-ee groundwater-was encountered in our borings or in the borings drilled by Granite Construction Company. We note that it is possible that groundwater conditions at the site may vary because of variations in rainfall, dewatering activities, irrigation, or other factors not apparent at the time our borings were drilled. f 20-1 108-18/2018RO96 Page 2 of 7 0) 10OR V1AinfP1ril i— an��ti�� i004 1