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1 ' 1444 MARIPOSA ROAD WKA No 2307 02 December 4, 1992 ' Page 3 mg/kg to 200 mg/kg, toluene concentrations ranging from 0 04 mg/kg to 1800 mg/kg, non-detectable ' concentrations of ethylbenzene, and total xylenes concentrations ranging from 0 019 mg/kg to 2100 g g mg/kg Based on these results, the excavation was deepened to approximately 36 feet below grade At ' 36 feet below grade, petroleum hydrocarbon odors were still noticeable in the soils so an exploratory trench was dug in the center of the excavation to a depth of approximately 44 feet below grade Test ' results for sample EXIT-44' revealed a TPH as gasoline concentration of 6800 mg/kg, a benzene concentration of 95 mg/kg, a toluene concentration of 550 mg/kg, a non-detectable concentration of ethylbenzene, and a total xylenes concentration of 670 mg/kg The excavation sample locations and ' depths are shown on Plate 2 Additionally, the laboratory test results for the excavation samples are summarized in Table 1 (attached), complete laboratory test results with chain-of-custody documentation are appended ' Tea composite samples were collected from p pthe stockpiles of soil generated during excavation by GeonAnaiytical Laboratories, Inc Test results for these samples revealed TPH as gasoline concentrations ranging from non-detectable levels to 370 mg/kg, non-detectable concentrations of benzene, toluene concentrations ranging from non-detectable levels to 430 mg/kg, ethylbenzene ' concentrations ranging from non-detectable levels to 53 mg/kg, and total xylenes concentrations ranging from non-detectable levels to 8900 mglkg Complete laboratory test results and chain-of-custody documentation for the stockpile samples are contained in the Appendix 1 ' PROPOSED SCOPE OF WORK The purpose of our work in the vicinity of the underground storage tanks will be to 'evaluate the ' horizontal and vertical extent petroleum hydrocarbon contamination resulting from tank and/or fuel pipeline leakage The scope of our work will include the drilling and sampling of four soil borings with a truck-mounted drill rig equipped with hollow-stem augers at the locations shown on Plate 2; the ' borings will be extended to approximately 75 feet below site grade or the ground water surface, whichever is encountered first Borings B1 and B4 will be drilled at an approximate 30-degree angle to vertical in order to obtain soil samples from directly beneath the former tanks Soil samples will be collected from the borings at five-foot maximum intervals with a modified ' California sampler equipped with clean, two-inch diameter, six-inch long stainless steel tubes, samples and drill cuttings will be described in the field using the Unified Soil Classification System (USCS) The sample tubes will sealed with polytetratIuoroethylene (PTFE)-coated sheets, plastic end caps and ' duct tape to reduce volatile hydrocarbon loss The samples will screened in the field with an organic • vapor analyzer (OVA) to evaluate potential hydrocarbon content Selected samples will be placed on ice and submitted under chain-of-custody to a California-certified laboratory for analysis of TPH as v `dW WALLACE KUHL Rec&d paper Er ASSOCIATES INC