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' SOIL VAPOR EXTRACTION PILOT STUDY REPORT San Joaquin County Montgomery Ward Auto Service Center Public Health Services Department 5400 pacific Avenue,Stockton CA Site Code 2163 ' from 0 0095 to 3 ppm Toluene at a concentration ranging from 0 0052 to 0 0062m was identified in both borings No other TPH-G or BTEX were Identified In soils obtained from ' borings MW-3 or MW-4 No TPH-G or BTEX were detected in any soil sample obtained from borings MW-5 or MW-6 ' with the exception of sample number MW-6 @ 49-50 5' which contained toluene at a concentration of 0 0052 ppm (see EAI, 1995) PHASE VII INVESTIGATION (1996) ' In 1996, EAI drilled and Installed four hydropunches (HP-1 through HP-4) and the constructed ground water monitoring well MW-7 (see Figure 2) The purpose of the Phase VII Investigation was to provide better data on the extent of dissolved hydrocarbons in ground water Hydropunch locations HP-1 and HP-2 were Installed east of Montgomery Ward wells MW-5 and MW-6 (see Figure 2) In EAI's opinion, the benzene concentrations detected in hydropunch HP-1 (36 2 ppb) and hydropunch HP-2 (3 ppb) are low enough to define the easterly edge of the dissolved ground water plume Hydropunches HP-3 and HP-4 and well MW-7 were Installed south of well MW-5 (see Figure 2) See Table 7 for testing results associated with soil samples collected as part of this Investigation No hydrocarbons were detected In the water samples collected from hydropunches HP-3 and HP-4 nor in the water sample collected from well MW-7 (see Table 8) Based on these testing results, the extent of hydrocarbons in ground water In a southerly direction did not extend to hydropunch HP-4 Therefore, the southerly edge of the dissolved phase ground water plume is between well MW-5 and hydropunch HP-4 Well MW-7 Is the most southerly boundary well I Further assessment west of existing Montgomery Ward well MW-4 was proposed as part of the Phase VII activities However, due to subterranean obstructions this work could not be completed Only a low level of benzene (1 3 ppb) was detected in Unocal well MW-17, which Is located westerly of Montgomery Ward well MW-2 (see Figure 2 and EAI, 1996) GROUND WATER TESTING RESULTS I Quarterly ground water sampling has been completed at the Montgomery Ward site from March 1993 (the first time ground water samples were collected from the site) to date ■ I IProject No 1232 A-4 ENVIRONMENTAL AUDIT, INC