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Mr. Kyle Christie Project 20805-146.006 <br /> August 5, 1996 <br /> Page 10 <br /> UST complex did not contain TPHG at concentrations exceeding the method reporting <br /> limits (TS-3, TS-4, and TS-5). <br /> Soil and fill material removed from the UST cavity (SP-1) were characterized and used to <br /> backfill the cavity at depths between 5 feet and 12 feet below grade. <br /> Soil samples collected in the vicinity of the former dispenser islands and product delivery <br /> piping contained TPHG concentrations of 2,000 to 12,000 mg/kg at depths of 6 to 9 feet. <br /> Soil samples collected along the third set of product delivery piping contained TPHG <br /> concentrations of 3.1 to 570 mg/kg. <br /> On-site soil aeration reduced TPH concentrations in the soil overexcavated from the <br /> former dispenser and piping areas (SP-2) from average concentrations of 818 mg/kg to <br /> 3.5 mg/kg. SJCPHS granted approval to use the aerated soil as backfill material. <br /> Excavation backfilling activities were completed on June 5, 1996, and the former UST <br /> complex, dispenser areas, and product delivery piping areas were resurfaced on <br /> June 6, 1996. <br /> The subsurface conditions in the vicinity of third dispenser and associated piping have not <br /> been characterized. Additional site assessment activities are proposed, including four <br /> additional vapor extraction wells completed with screen intervals of approximately 5 to <br /> 25 feet bgs. The additional vapor extraction wells were proposed after evaluating the <br /> extent of soil impacts and the existing vapor extraction well network. As shown on <br /> Figure 5, installation of the four proposed vapor extraction wells to supplement the existing <br /> vapor extraction well network will provide coverage of the former UST complex and the <br /> vicinity of the third dispenser and associated piping at depths of 5 to 25 feet bgs. Details <br /> regarding site characterization and vapor extraction well installation are presented in the <br /> June 19, 1996, "Workplan for Additional Subsurface Investigation." <br /> RECOMMENDED REPORT DISTRIBUTION <br /> We recommend copies of this report be distributed to the following: <br /> Mike Infurna <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P.O. Box 388 <br /> Stockton, California 95201-0388 <br /> SAC\ �PJM80M8051460.6[)5-95\cjb:3 <br />