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' SOIL VAPOR EXTRACTION PILOT A WORK PLAN � San Joaquin County Montgomery Ward Auto Service Center Public Health Services Department 5400 Pacific Avenue, Stockton, CA Site Code 2163 I from 0 0095 to 3 ppm Toluene at a concentration ranging from 0 0052 to 0 0062 ppm 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) SOIL TESTING RESULTS I It is EAI's opimon that the extent of unsaturated zone soil contamination has been adequately defined at the Montgomery Ward site Figures 5 and 6 are cross-sections which depict the extent of soil contamination /ti",r%YTkTY% i197 A ri Wr Wlk rVT4C+r11Y'kTd- 71TC'irV mc• ■ L71%"U1'1U VYtili,IL li.O111,1" 1LGaULIa I Table 8 contains the results of quarterly ground water sampling completed at the Montgomery Ward site between March 1993 (the first time ground water samples were collected from the site) and March 1996 Project No 1232 A-4 ENVIRONMENTAL AUDIT, INC