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Quarterly Report - March 1999 LARRY'S AUTO REPAIR 308 North Grant Street, Stockton, California 1.0. INTRODUCTION AND SCOPE OF WORK At the request of Mr Charles Skobrak,Advanced GeoEnvironmental, Inc ,(AGE) has prepared this report summarizing ground water monitoring activities performed at 308 North Grant Street, Stockton, California Quarterly ground water monitoring was conducted on 23 March 1999 The location of the site is illustrated in Figure I - Location Map Structures and well locations are Iillustrated on Figure 2 -Site Plan Background information was summarized in Quarterly Report- August 1997 prepared by AGE 2.0. PROCEDURES IField work was performed in accordance with San Joaquin County Public Health Services - Environmental Health Division (PHS-EHD) and Regional Water Quality Control Board - Central Valley Region(RWQCB-CVR) guidelines for the investigation of underground storage tank (UST) sites 2 1 MONITORING WELL PURGE PROCEDURES On 23 March 1999, an Ullage interface probe was used to measure the depth to ground water and to check for the presence of free product in five monitoring wells and five vapor wells at the site ' relative to the tops of the well casings The ground water elevations,ground water flow direction and hydraulic gradient were determined from these data (Table 1) After measuring ground water depths, monitoring wells MW-1, MW-2, MW-3, MW-4 and MW-7 and vapor wells VW-213, VW-3, VW-4, VW-513 and VW-5C were purged using a Grundfos submersible purge pump The purge pump was decontaminated prior to purging each well using an Alconox solution and clean rinse water Approximately 6 to 20 gallons of water were removed from each purged well (minimum of three well-volumes for each well) Water was purged from near the top of the water surface to assure removal of stagnate water trapped within the non-screened section Iof the drown wells Temperature, pH and conductivity were measured at regular intervals during purging The pH meter failed during purging at the site Therefore only readings for wells MW-3 and MW-7 are accurate and were transcribed to the stabilization data tables The measured properties of the purged water and the field sheets are included in Appendix A The purged water was stored on- site in 55-gallon DOT drums pending laboratory analyses Adranced GeoEmironmental,Inc