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r <br /> m <br /> i <br /> 1 . <br /> 3 EXCAVATION AND SAMPLE COLLECTION <br /> t. . <br /> 3 < Excavation and removal of waste oil contaminated soil was initiated on January 16, 1990. <br /> By the late afternoon on January 17, 1990, approximately 100 cubic yards of contaminated <br /> l soil had been removed for disposal at the Amador County Landfill. Approximately 20 <br /> f' cubic yards of clean soil had been removed and stockpiled on-site for later use as fill <br /> material. The completed excavation was rectangular in shape, approximately 17 x 15 feet <br /> and 13 to 14 feet in depth. The static water level was approximately 12 feet below the <br /> asphaltic cover of the facility's parking Iot. <br /> The upper 3 feet of material excavated consisted primarily of fill material including brick, <br /> bottles, stucco and concrete as well as silt and sand. The near surface native soil consists <br /> e� prima►zly dark brown to buff colored silty clay with small lenses of silty sand. The <br /> r=- <br /> Lam; <br /> waste oil, absorbing onto the clay-rich material had turned the soil a dark gray, providing <br /> a means to visibly distinguish between contaminated and noncontaminated soils (see <br /> photographs in Appendix 1). The excavation of soil continued until no visible trace of <br /> contamination was left in the north east and west walls of the excavation. The south wall <br /> 6 of the excavation was located adjacent to the dealership's service garage, approximately 4 <br /> j„ feet from the building. The proximity of the building precluded extensive excavation <br /> �.: toward the south. Because further excavation of the south wall was not attempted, minor <br /> contamination was still visible in an elongated area on the wall about 4 feet above the <br /> water table. <br /> 3.1 Soil Sample Collection E <br /> L' <br /> Soil samples were collected from each wall of the excavation just above the soil <br /> -{_ -- groundwater interface. The .c <br /> ._sail-samples- ollected-from.-the--north,-east-and-west--walls-- -- -- - ----=- <br /> -- ---- ,.� terra <br /> were obtained from a backhoe bucket containing native soil. The samples were then <br /> collected by driving a clean 2 x 6-inch brass tube into the soil with a mallet. Following <br /> - 6 <br />