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SOIL VAPOR EXTRACTION PILOT STUDY WORK PLAN San Joaquin County Montgomery Ward Auto Service Center Public Health Services Department 5400 Pacific Avenue Stockton CA Site Code 2163 In cross-section (see Figure 4 for location), the first plume below the former gasoline UST ' excavation extends from approximately 15 feet below ground surface (bgs) to approximately 40 feet bgs (see Figure 5 ) The plume appears to be fairly uniform in its lateral extent at all depths from surface to the ground water table However, the plume shows higher concentrations in soil at deeper zones The cross section of the second plume (see Figure 4 for location), extends from approximately 15 feet bgs to approximately 40 feet bgs (see Figure 6 ) In this plume, the maximum contaminant concentrations in soil are found at shallow depths 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 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 Ground water flow as recorded in March 1996 was in the easterly direction with an approximate gradient of 0 005 foot/foot (see Figure 7 ) 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 Figure 8 shows ground water flow in a southerly direction in September 1995 The reason for this fluctuation is presently unknown However, it is suspected that San Joaquin Delta College (SJDC), located southwesterly of the Montgomery Ward site, may extract ground water from its campus (see Figure 1) EAI has written SJDC requesting information I on the extraction of ground water from its campus No information-leas been received from SJDC 3.4 SCOPE OF WORK This section presents the scope of work to be completed in this pilot study Appendix B contains a copy of the health and safety plan The following paragraphs give details on each task 3.1 TASK 1 - PERMITTING 3 1 1 San Joaquin County Public Health Services Department Montgomery Ward will submit this Work Plan to the San Joaquin County Public Health Services Department (SJCPHSD) for review and approval Once approved, this Work Plan I will be used as a supporting document for all other approvals/permits required to complete the pilot study Project No 1232 - 2 - ENVIRONMENTAL AUDIT, INC