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i <br /> Quarterly Report - Fourth Quarter 2003 <br /> Former CHASE CHEVROLET (Van Buren) Facility <br /> 424 North Van Buren Street, Stockton, California <br /> 1.0. INTRODUCTION <br /> At the request of the City of Stockton,Advanced GeoEnvironmental, Inc (AGE) has prepared this <br /> quarterly report summarizing field activities performed during the fourth quarter of 2003 at <br /> 424 North Van Buren Street(the site), Stockton, California The scope of work included conducting <br /> a quarterly groundwater monitoring event and operation of an ozone-sparging system at the site The <br /> site setting is illustrated in Figure 1 Structures and monitoring well locations are illustrated in <br /> Figure 2 <br /> Background information was summarized in Corrective Action Plan - December 1996, dated <br /> 27 December 1996 and in Quarterly Report-May 1999,dated 30 July 1999,both prepared by AGE <br /> Historical quarterly monitoring data is included in the tables of this report <br /> . 2 0. PROCEDURES <br /> Field activities were performed in accordance with guidelines issued by the Central Valley Regional <br /> Water Quality Control Board (RWQCB) and by the San Joaquin County Environmental Health <br /> Department (EHD) for investigations of underground storage tank (UST) sites and sampling of <br /> ground water monitoring wells, respectively <br /> 2 1 In-Situ OZONE SPARGE SYSTEM OPERATION <br /> Operation of the ozone sparge system was initiated in July 2003 The ozone system operated <br /> continuously during the fourth quarter 2003 The ozone generator is equipped with solenoid valves <br /> to control the distribution of ozone to each sparge well Ozone is cycled through each valve for one- <br /> hour intervals utilizing a computer controlled timer Based on the average sparging period per day <br /> per well, approximately 0 03 pounds of ozone is sparged at each well during a 24-hour period <br /> A calculation for ozone sparge rates is included in Appendix A <br /> 2 2 QUARTERLY WELL MONITORING PROCEDURES <br /> A quarterly ground water monitoring event was performed on 29 and 30 October 2003 The ground <br /> water monitoring was performed in accordance with the revised monitoring schedule established <br /> . during a meeting with EHD staff on 25 September 2002 <br /> Advanced GeoEnvironmental,Inc <br />