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1.0 INTRODUCTION This quarterly ground water monitoring report and case closure request was prepared by American Geological Services, Inc. for Western Refrigerating & Cold Storage Company. ' As part of the ongoing quarterly monitoring program, this report details all field activities performed on March 24, 2004 at the Tracy Cold Storage site and the results of these activities. The following sections describe the methodology employed and the results ' obtained during this sampling event. Historical ground water analytical data are also provided for each of the previous sampling events. ' It is the opinion of American Geological Services that the reductions in contaminant mass observed at this site warrant case closure. The reduction in contaminant mass has been ' achieved by the removal of approximately 1,522 cubic yards of gasoline impacted soil, the addition of Oxygen Release CompoundO to the subsurface, and other natural attenuation factors. Additionally, the strong adsorptive capacity of the soil will significantly limit migration of residual contaminants. Significant decreases in the levels of toluene, ethyl benzene and total xylenes have been indicated since September 1998 in MW-1/MW-IA, with reductions ranging between 83% and 99%. This well is located adjacent to the former UST and is representative of conditions in the former source area. Immediately following the performance of the remedial excavation a reduction of 54% in gasoline and 80% in benzene was observed at MW-1/MW-IA. Since the September 1998 ground water sampling event, further reductions of more than 77% were reported for both gasoline and benzene. . A new water supply 1 well was installed to the south of the remedial excavation. The South Well was taken out of service to allow for inspection by downhole video ' equipment. The results of the inspection indicate that a proper shallow well seal was not in place, and therefore the South Well was abandoned. The new water supply well was installed in accordance with current San Joaquin County standards, and is the replacement for the South Well. The outline provided in Table I of Appendix B, Tri-Regional Board Staff Recommendations for Preliminary Investigations and Evaluation of Underground Tank Sites, No Further Action=Requests, draft revision dated October, 1996 has been followed, ' and the relevant information is included as part of this report. ' 1.1 Site Description The Tracy Cold Storage site is located at 24500 S. MacArthur Road in Tracy, California ' (Figure 1). The property includes approximately eight acres of land that is utilized as a commercial cold storage facility for agricultural products. The site is bounded on three sides by undeveloped agricultural land. The northern boundary of the property is shared with the Southern Pacific Railroad. American Geological Service, Inc. tCA95DE-029 I