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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 remediation efforts, should the be necessary, must in EAI's Y az'y, opinion, be addressed jointly by Montgomery Ward and Unocal 2.4 BACKGROUND ' This sectionresents a summary ary of the soil and ground water Investigations performed at this site to date, the results obtained from these Investigations and a summary of the geology and ' hydrogeology of the site 2.1 Previous Investigations ' Several site assessments have been completed to date to attempt to define the extent of soil and ground water contamination beneath the Montgomery Ward site Appendix A provides a ' descriptive summary of each assessment, the results obtained and the conclusions made Tables 1 through 7 present the analytical testing results of testing soil samples collected from the Montgomery Ward site prior to this pilot study Figure 2 shows the locations of all ' borings and wells installed at the site prior to this pilot study Table 8 presents the analytical testing results of ground water samples obtained prior to this pilot study � 2.2 Geology The geology at the Montgomery Ward site consists of alternating sand, silt and clay layers A silt layer extends from the surface to about 30 feet below ground surface (bgs) The silt layer ' is underlain by a layer of sand, silt and clay layer that appears to be locally pinching This layer extends from approximately 30 to 50 feet bgs A coarse sand zone extends downward from approximately 50 feet bgs and forms the first water bearing zone 2.3 Hydrogeology Ground water beneath the Montgomery Ward site is encountered at approximately 50 feet bgs in the sand unit EAI has performed quarterly ground water monitoring at the Montgomery Ward site since March 1993 The ground water gradient appears to fluctuate between an easterly and southerly direction at different times of the year Ground water flow as recorded I in March 1996 was in the easterly direction with an approximate gradient of 0 005 foot/foot (see Figure 3) Figure 4 shows ground water flow in a southerly direction in September 1995 The reason for this fluctuation Is suspected to be an irrigation well located near the southwest corner of Pacific Avenue and Robinhood Drive This well is pumped seasonallv by San Joaquin Delta College (SJDC), located southwesterly of the Montgomery Ward site (see I Figure 1) EAI has obtained information on the extraction of ground water from the SJDC campus and has forwarded that information to San Joaquin County Public Health Services (SJCPHS) As directed by the SJCPHS, EAI has tested ground water samples from that well EAI is currently attempting to obtain additional information regarding this well I, II Project No 1232 - 2 - ENVIRONMENTAL AUDIT, INC