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It <br /> 1.0 INTRODUCTION <br /> ' This quarterly ground water monitoring report and case closure request was prepared by <br /> American Geological Services, Inc. for Western Refrigerating & Cold Storage Company. <br /> ' As part of the ongoing quarterly monitoring program, this report details all field activities <br /> performed on June 15 and 22, 1999 at the Tracy Cold Storage site and the results of these <br /> activities. The following sections describe the methodology employed and the results <br /> obtained during this sampling event. Historical ground water analytical data are also <br /> provided for each of the previous sampling events. <br /> ' It is the opinion of American Geological Services that the reductions in contaminant mass <br /> observed at this site warrant case closure. The reduction in contaminant mass has been <br /> t achieved by the removal of approximately 1,522 cubic yards of gasoline impacted soil, <br /> the addition of Oxygen Release Compound® to the subsurface, and other natural <br /> attenuation factors. Additionally, the strong adsorptive capacity of the soil will <br /> significantly limit migration of residual contaminants. <br /> Immediately following the performance of the remedial excavation a reduction of 54% in <br /> ' gasoline and 80% in benzene was observed at MW-1/MW-IA. Since the September <br /> 1998 ground water sampling event, further reductions of more than 77% were reported <br /> ' for both gasoline and benzene. Significant decreases in the levels of toluene, ethyl <br /> benzene and total xylenes have also been indicated since September 1998, with <br /> reductions ranging between 83% and 99%. This well is located adjacent to the former <br /> UST and is representative of conditions in the former source area. <br /> The outline provided in Table 1 of Appendix B, Tri-Regional Board Staff <br /> ' Recommendations for Preliminary Investigations and Evaluation of Underground Tank <br /> Sites, No Further Action Requests, draft revision dated October, 1996 has been followed, <br /> and the relevant information is included as part of this report. <br /> 1.1 Site Description <br /> ' The Tracy Cold Storage site is located at 24500 S. MacArthur Road in Tracy, California <br /> (Figure 1). The property includes approximately eight acres of land that is utilized as a <br /> ' commercial cold storage facility for agricultural products. The site is bounded on three <br /> sides by undeveloped agricultural land. The northern boundary of the property is shared <br /> with the Southern Pacific Railroad. <br /> ' <br /> Approximately 44,000 square feet of cold storage space, various maintenance buildings, <br /> , <br /> and an office are located on the property. Water is supplied by two on-site wells. A <br /> ' septic system is located on-site. <br /> American Geological Service, Inc. <br /> ' CA95DE-029 1 <br />