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Mr. Kenneth Earnest Ultramar Inc. March 21, 1995 Page 3 Analytical test results indicate that only one soil sample (TI-B) collected from tank basin on February 28, 1995, contained detectable concentrations of petroleum hydrocarbons. None of the samples collected after overexcavation of the tank basin on March 2, 1995, contained detectable concentrations of TPH as gasoline; however, sample TB-2 contained ethylbenzene at a concentration of 0.016 mg/kg and total xylenes at a concentration of 0.20 mg/kg. None of the soil samples collected from beneath the product lines and pump islands on February 28, 1995, contained detectable concentrations of TPH as gasoline or BTEX except sample P12-B, which contained benzene at a concentration of 0.0079 mg/kg and total xylenes at a concentration of 0.0071 mg/kg. None of the soil samples collected after overexcavation of the pump island area on March 9, 1995, contained detectable concentrations of petroleum hydrocarbons. Concentrations of WET lead in the samples collected from the excavations were relatively low and were typical of background concentrations which might be expected in samples of native soil from this area. Soil Stockpiles Approximately 1,075 cubic yards of soil were removed from the fuel tank and pump island excavations. The excavated soil was stockpiled on site pending laboratory analysis of stockpile samples. Four soil samples were collected from each 50 cubic yards of stockpiled soil. Each set of four samples was composited by West prior to analysis for BTEX and TPH as gasoline. Analytical results from the composite stockpile samples are summarized in Table 2, and copies of the analytical laboratory reports are included in Enclosure A. Subsequent to laboratory analysis, the stockpiled soil was transported by Ben's Trucking and Equipment Company to the Bioindustries Inc. facility in Red Bluff, California, for recycling. Discussion i Analytical results for soil samples collected during this investigation, and for soil samples collected I from soil borings SB-1, SB-2, and SB-3 (as reported in Delta's Subsurface Investigation Report, dated July 27, 1993), indicate that vapor extraction and excavation have removed nearly all detectable concentrations of petroleum hydrocarbons from soil underlying the site. The concentrations of petroleum hydrocarbons remaining in soil at the site are unlikely to pose a threat to human health or ground water quality. Analytical results for ground water samples collected from the site monitoring wells have not contained detectable concentrations of petroleum hydrocarbons, except for a ground water sample collected from monitoring well MW-4 on May 20, 1992. This sample contained TPH as gasoline at a concentration of 68 micrograms per liter, but did not contain detectable concentrations of BTEX. Cumulative water table elevations and ground water analytical results compiled by other consultants are presented in Enclosure B. Recommendations I Based on the soil and ground water sample analytical results, Delta believes that regulatory closure of this site is warranted. We recommend that the existing ground water monitoring wells be destroyed and that no further investigation or remediation be conducted.