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1 • Quarterly Report - July 1999 CALIFORNIA FUELS CARDLOCK STATION ' 2402 Pacific Avenue, Stockton, California ' 1.0. INTRODUCTION ' Advanced GeoEnvironmental, Inc (AGE) has prepared this Quarterly Report for 2402 Pacific Avenue, Stockton, California The site setting is illustrated on Figure 1 Site structures and monitoring well locations are depicted on 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 established by the San Joaquin County Public Health Services - Environmental Health Division (PHS-EHD) and by the Central Valley Regional Water Quality Control Board (CVRWQCB) for investigation of underground storage tank (UST) sites A ' summary of previous investigations at the site was included in the Corrective Action Plan- May 1998, dated 05 May 1998 and prepared by AGE Analytical data acquired to date is included in this ' report ' • 2.0. QUARTERLY MONITORING AND SAMPLING PROCEDURES On 26 July 1999, ground water monitoring was performed at wells MW-1 through MW-12, VW-1, ' VW-2,AWA B and AW-2B, on 27 July 1999, ground water sampling was performed at wells MW-1 through MW-4, MW-6 through MW-10, MW-12 and VW-1 Groundwater monitoring procedures for the site were outlined in Work Plan Addendum - June 1998, dated 08 June 1998 prepared by ' AGE and approved by the PHS-EHD by letter dated 30 June 1998 ' 2 1 MONITORING WELL PURGE PROCEDURES Depths to ground water were measured in each well from the tops of the well casings at the site to tthe 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) After water levels were measured, approximately 6 to 12 gallons of ground water (a minimum of three well-volumes per well) were removed from wells MW-1 through MW-4, MW-6 through MW- 12, VW-1, AW-1B and AW-2B utilizing a two-stage submersible pump (purge pump), the purge pump was initially set at the top of the water column and then slowly lowered to the total depth of each well Approximately 2 gallons of ground water were removed from well MW-1 I before being pumped"dry" Temperature, pH and conductivity were measured for stabilization at regular purge- '