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' Quarterly Report - First Quarter 2003 • CALIFORNIA FUELS CARDLOCK STATION ' 2402 Pacific Avenue, Stockton, California ' 1.0. INTRODUCTION ' At the request of Mr David Atwater,Advanced GeoEnviromnental, Inc (AGE) has prepared this quarterly report documenting the procedures and results for a ground water monitoring event performed at 2402 Pacific Avenue (the site), Stockton, California, the report also documents ' December, January, February and March 2003 progress of the in-situ air sparging (IAS) and soil vapor extraction (SVE) recovery system The objectives of the site activities were to monitor dissolved petroleum hydrocarbon concentrations in ground water, to assess ground water flow ' direction and gradient and to monitor the progress and effectiveness of SVE and IAS remediation at the site The site setting is illustrated on Figure 1 Site structures and monitoring well locations are depicted on Figure 2 This report has been 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 A summary of previous investigations at the site was included in the AGE-prepared Corrective Action Plan-May 1998,dated 05 May 1998 Analytical data acquired to date is included in this report I• 2.0. GROUND WATER MONITORING AND SAMPLING PROCEDURES ' On 04 April 2003, round water monitoring was performed at the site on single-level wells MW-1 P g g through MW-12, multi-level well MW-13 and air sparge wells AW-1 (A and B) and AW-2 (A and ' B) Ground water monitoring procedures for the site were outlined in Work Plan Addendum, dated 16 May 2000 and conform to ground water monitoring guidelines issued by the SJCEHD As built ' construction details of all monitoring wells are summarized in Table 1 ' 21 WELL MONITORING AND EVACUATION PROCEDURES The depth to ground water was measured at each well from the tops of the well casings to the nearest 0 01-foot,utilizing a Solinst water level meter Ground water elevation at the site was calculated by subtracting the measured depth to ground water from the surveyed well casing elevations (Table 1) Ground water elevations were plotted and contoured on a scaled site map (Figure 3) ' After water levels were measured, approximately 51/2 to 10 gallons of ground water(a minimum of three casing-water volumes per well)were evacuated (purged) from single-level monitoring wells and shallow (screen interval A) air sparge wells utilizing a polyethylene disposable bailer, approximately 1-gallon of ground water was removed from well MW-11 before being purged"dry" Temperature,pH and conductivity of purged water were measured from each well for stabilization I 1