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IQuarterly Report - Second Quarter 2001 PACIFIC CAR WASH ' 4405 Pacific Avenue, Stockton, California ' 1.0. INTRODUCTION AND SCOPE OF WORK ' Advanced GeoEnvironmental, Inc (AGE)has prepared this quarterly report for 4405 Pacific Avenue (the site), Stockton, California The site setting is illustrated in Figure 1 Site structures and monitoring well locations are depicted in Figure 2 The objective of the work was to monitor dissolved petroleum hydrocarbon concentrations in ground water and to characterize ground water flow direction and gradient on the site This report is prepared ' in accordance with guidelines issued by the California Regional Water Quality Control Board (RWQCB) - Central Valley Region for investigation of underground storage tank (UST) sites, monitoring wells were sampled in accordance with guidelines issued by the San Joaquin County ' Public Health Services - Environmental Health Division (PHS-EHD) A summary of previous investigations at the site was included in the Preliminary Site Investigation and Evaluation Report - January 1997, dated 15 January 1997, prepared by AGE lie Z.O. PROCEDURES On 26 June 2001, groundwater monitoring and sampling were performed at the site on wells MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, MW-8, MW-9, MW-10A and MW-10B (MW-1 through MW-10) Ground water monitoring procedures for the site were outlined in the Work Plan Addendum -June 1998, dated 10 June 1998, prepared by AGE and approved by the PHS-EHD by letter dated 24 June 1998 I21 MONITORING WELL PURGE PROCEDURES Depths to ground water were measured in each well from the tops of the well casings to the nearest 0 01-foot utilizing a Solinst water level meter Ground water elevations in each well at the site were calculated by subtracting the measured depth to ground water from the surveyed casing elevations (Table 1) Ground water elevations were plotted and contoured on a scaled site map (Figure 3) Hfter water leveis were measurea, approximately 6 to 13 gallons of ground water (a minimum of three casing-water volumes per well) were removed from wells MW-1 through MW-10 utilizing a two-stage teflon submersible pump or by hand bailing with a disposable bailer, approximately 8 gallons of water were purged from MW-1 before being pumped "dry" Temperature, pH and conductivity were measured for stabilization at regular purge-volume intervals from each well using either an Oakton water analyzer or an ICM water analyzer Field data and logs are included with Appendix A Purged ground water was containerized in 55-gallon drums and was stored on-site in an area lacking general public access Advanced CeoEnvironmental,Inc