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' Quarterly Report ort - March 1999 TOP FILLING STATION 101 South Wilson Way Stockton, California 1.0. INTRODUCTION Advanced GeoEnvironmental, Inc (AGE) has prepared this Quarterly Report for 101 South Wilson Way, Stockton, Caltfonua The site setting :s illustrated on Figure 1 Site structures and momtornng ' 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 Quarter ly Report- October 1996, ' dated 22 November 1996, prepared by AGE 2.0. QUARTERLY MONITORING AND SAMPLING PROCEDURES On 26 March 1999, ground water monitoring and sampling was performed at wells MW-1 through ' MW-5, VW-I C, VW-2A and VW-3A Ground water monitoring procedures for the site were outlined in Work Plan Addendum, dated 08 November 1995 and approved by the PHS-EHD by letter dated 27 November 1995 ' 21 MONITORING WELL PURGE PROCEDURES Depths to ground water were measured from the top of each well casing 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 from surveyed casing elevations (Table 1) Ground water elevations were plotted and contoured on a scaled site map (Figure 3) After water levels were measured, between fifteen and twenty gallons of ground water (a minimum of three-well volumes per well) were removed from wells MWA through MW-5 and V WA C through VW-3A utilizing a submersible Grundfos Redt-flow pump or a two-stage submersible pump, the first two gallons were removed utilizing a teflon bailer and new rope to be sure to remove I stagnant water from drowned wells 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 with Appendix A Purged ground water was contaxnenzed in 55-gallon drums and was stored on-site in an area lacking general public access IA&4nred GeoEn\Ironmental,inc L