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1 ' 1 Quarterly Report - May 1998 ' FORMER CHASE CHEVROLET (VAN BUREN) FACILITY 424 North Van Buren Street, Stockton, California ' 1.0. INTRODUCTION ' In accordance with a request from Mr Jeffery Setness of Hartmann & Setness, Advanced GeoEnvironmental, Inc (AGE) has prepared this Quarterly Report summarizing field activities performed during the second quarter of 1998 at 424 North Van Buren Street, Stockton, California ' (Figure I -Location Map) The scope of work included monitoring ground water,collecting ground water samples,obtaining laboratory analyses of the samples and preparation of this report Structures ' and monitoring well locations on the site and adjacent area are illustrated in Figure 2 - Vicinity Map Field activities were performed in accordance with guidelines established by the Regional Water ' Quality Control Board - Central Valley Region (RWQCB-CVR) and by the San Joaquin County Public Health Services - Environmental Health Division (PHS-EHD) for the investigation of underground storage tank (UST) sites Background information was summarized in the Corrective ' Action Plan - December 1996 and subsequent quarterly reports prepared by AGE • 2.0. PROCEDURES 21 MONITORING WELL PURGE PROCEDURES On 07 May 1998 a Solinst water level meter was as used to measure the depth to ground water in each well relative to the tops of the well casings An Ullage interface probe was used to check for the presence of free product in MW-3 and MW-9 The relative ground water elevations and hydraulic gradient were determined from these data(Table 1) On 08 May 1998,each monitoring well was purged using atwo-stage submersible purge pump The pump was decontaminated prior to purging each well using an Alconox solution and clean tap water Temperature,pH and conductivity of purged water were measured at regular intervals during purging using an ICM model 52200 water analyzer Approximately ten to fifteen gallons of water (a minimum of three well volumes) were removed from each well except MW-9, from which sixty gallons of water were purged All purged water was stored in 55-gallon DOT-approved drums on- site Field data and field logs are included in Appendix A 5 22 COLLECTION OF GROUND WATER SAMPLES IWater samples were collected from each well using new, disposable bailers and,upon retrieval,were transferred into 40-m1 EPA-approved VOA vials containing 0 5 ml of 18%hydrochloric acid as a sample preservative The samples were labeled and transported under chain-of-custody, in a chilled Advanced GeoEnvironmentai,Inc