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"'T M PROBLEM ASSESSMENT REPORT/IIVTERIM REMEDIAL ACTION PLAN -10- Former Beacon Station No. 494, 2185 East Fremont Street Stockton, CA--AMV Project No. 19005.07 ' is required to confirm the July 1993 ground water flow direction. Alternatively, ground water flow directions may fluctuate locally in response to changing recharge patterns or ground water ' pumping in the area. As of July 1993, a unique ground water flow direction is not suggested by the ground water analytical data. While monitoring well MW-3 has consistently contained the highest dissolved benzene concentrations, the next highest concentration has been detected at different times in samples collected from monitoring wells MW-4 (December 1992 and February and April 1993) and MW-2 (July 1993). Free product has never been detected in monitoring wells at the site. Historical ground water analytical results suggest that the extent of dissolved petroleum constituents in ground water has been defined on the southeast (monitoring well MW-4) and the northwest (monitoring well ' MW-5). Pending results of additional water level measurements, additional delineation wells may be necessary either northeast of monitoring well MW-1 or southwest of monitoring well MW-2. 5.3 Presence of Chlorinated Compounds in Ground Water ' The detection of dissolved chlorinated solvents in the sample collected from monitoring well MW-5 may be attributed to the existence of a machine shop along the property's western boundary. Significantly, these compounds were not detected in ground water samples collected from any other monitoring wells at the site. This detection may also provide evidence of the prevailing direction of local ground water flow (see discussion above). 6.0 AQUEFER AND SOEL VAPOR EXTRACTION TESTING ' 6.1 Aquifer Pumping Test From July 1 through 19, 1993, AMV conducted an extended aquifer pumping test at the site to evaluate aquifer characteristics of the water-bearing strata beneath the site. The test utilized monitoring well MW-3 as the pumping well. Monitoring well MW-3 was selected because ' ground water samples collected from this well indicated the presence of elevated concentrations of petroleum constituents, and because conceptual remediation plans anticipated that long-term pumping of monitoring well MW-3 would be desirable. As described below, AMV conducted ' the pumping test in two phases. Phase 1 was a 48-hour continuous pumping test, and phase 2 was a 12-day intermittent pumping test. ' rptoos.w