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Report on Subsurface Environmental Exploration (Soil Borings) Page 5 A & M Market, 4579 East Acampo Road, Acampo, California November 9, 1992 Quorum Environmental Consultants, Inc , Project 92-120-2 shown on Table 1 EDB and EDC were not detected in any of the samples Lead was detected in concentrations ranging from 6 to 14 parts per million As an appropriate response to the initial findings, Quorum proposed an excavation program to remove hydrocarbon-bearing soil from the tank cavity until either hydrocarbon concentrations in soil remaining in place were acceptable to the SJCLHD or until the safe operating limit of the equipment had been reached On September 28, 1992, a geologist from Quorum was at the site to supervise SSMC in excavating additional soil from the gasoline tank cavity Mr Michael M Collins of the San Joaquin County Public Health Services, Environmental Health Division, (SJCPHS)was on site during excavation SEMC used an excavator to remove soil below the east ends of the former tanks T-1 and T-3, to an approximate depth of 15 feet where two samples were collected Two test pits were then dug into the west side of the base of the excavation ' to an approximate depth of 22 feet, which was the safe operating limit of the excavator Soil brought to the surface in the excavator bucket from each location produced hydrocarbon vapors in concentrations greater than 1,000 ppm, as measured using a photoionization detector (PID) Two samples were collected from the bottoms of the two test pits, which were 22 feet below grade. Locations of the test pits are shown on Figure 3 The results of the laboratory analyses on these samples are shown in Table 1, and the Chain-of-Custody Record and the laboratory analytical reports are presented in Appendix D The laboratory test results show that the samples from the east side of the tank cavity do not contain hydrocarbons above the laboratory detection limits, but the samples from the test pits (to 22 feet deep) on the west side of the cavity do contain hydrocarbons Because the safe operating limit of the excavator had been reached, it was fudged impractical in the field to remediate hydrocarbon-bearing soil through continued excavation Sav-Mor Oil Co. then requested that Quorum drill soil borings around the tank cavity to begin delineating the vertical and lateral extent of hydrocarbons in soil to provide additional data for better evaluating remedial options 4.0 FIELD EXPLORATION 4.1 Background ' Hydrocarbon contamination in the form of gasoline was detected in the tank pit during removal of the underground storage tanks in 1992 Samples of soil from below the east ends of the tanks showed nondetectable levels of hydrocarbons. Further excavating and trenching in the base of the tank pit showed hydrocarbons in soil from 22 feet deep along the west side of the tank pit This depth was prohibitive to further excavation, accordingly, advancement of soil borings was necessary to assess levels of hydrocarbons