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s Quarterly Report - July 1999 ' 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, 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 ark 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 Preliminary Site Investigation and Evaluation Report-January 1997, dated 15 January 1997, and prepared by AGE 2.0. PROCEDURES On 28 Jul 1999, round water monitoring was performed at the site on wells MW-1 through MW- 10, ground water samples were collected from the above referenced wells on 29 July 1999 Ground water monitoring and sampling 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 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 ' 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 fiom 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-2 through MW-10 utilizing a two-stage submersible pump, ground water pumping was initiated at the top of the water column and the pump was slowly lowered to total depth to purge ground water within the entire well casing Approximately 6 gallons of ground water were removed from well MW-1 before being pumped "dry" Temperature, pH and conductivity were measured for stabilization at regular purge-volume intervals from each well using an ICM Model 52200 water analyzer Field data and logs are included Advanced GeoEn,*iron mental,Inc