SITE INFORMATION AND CORRESPONDENCE

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4 Ms.Lori Duncan November 15,2011 RE:2911 E.Fremont St,Stockton,CA Page 5 of 14 contained no detectable petroleum hydrocarbons. The soil sample collected from the northern portion of the east wall at a depth of approximately 15 feet(ENW-15.0)contained TPHg at a concentration of 670 milligrams per kilogram(mg/kg). The sample collected from the south wall at a depth of approximately 14 feet bgs(SW-14.0)contained TPHg at a concentration of 310 mg/kg. Soil samples collected from the excavation floor contained TPHg at concentrations of 1,100 mg/kg (western portion of the excavation floor)and 120 mg/kg(eastern portion of the excavation floor). No benzene or MTBE was detected in any confirmation soil sample, but other gasoline components were detected at various concentrations. Table 1 summarizes analytical results of soil samples collected near the inactive clarifier.Attachment 1 contains a copy of the laboratory report. Figure 5 presents a site plan detail of the excavation area, including sample locations and concentrations of TPHg in soil samples. Figure 6 presents a cross section showing the excavation limits, soil sample locations, and estimated extent of residual TPHg contamination in soil. Summary of Soil Stockpile Sampling and Disposal Excavated soil was temporarily stockpiled on a concrete surface just west of the entrance to the warehouse. The soil stockpile was covered with plastic pending removal for disposal. Soil samples were collected from the stockpiled soil and analyzed by Argon Laboratories in order to characterize the nature of contaminants in the excavated soil and coordinate disposal. Four soil samples were collected into 2- inch diameter brass tubes on June 20, 2011, sealed at each end with Teflon®tape and plastic end caps, labeled, and placed in an ice chest cooled to a temperature of approximately 4° C. The samples were transported to Argon Laboratories where they were combined into a single 4:1 composite sample and analyzed for TPHg by EPA 8015M, VOCs by EPA 8260B, LUFT Metals (cadmium, chromium, lead, nickel, zinc) by EPA 6010B, and soluble chromium by CA WET/EPA 6020A. Based upon the preliminary laboratory results, officials at Forward Landfill in Manteca, California(Republic Services, Inc.) requested that the composite sample also be analyzed for leachable VOCs by extraction method SW1311 (ZHETCLP)/SW5030B and EPA 8260B. After reviewing the analytical results of the soil stockpile composite samples, Republic Services, Inc. authorized disposal of the soil at Forward Landfill and the soil was transported for disposal on July 1, 2011. A total of 211.23 tons of soil was transported to Forward Landfill by GCU Trucking (State Transportation Number 45745). Attachment 2 contains a copy of the laboratory reports related to the soil stockpile as well as a record of soil transported to the landfill. Area Restoration Clean backfill material was transported to the site by GCU Trucking beginning July 1,2011. Pea gravel was used to backfill the excavation to within approximately four feet of the ground surface prior to repairing the sewer line by installing a new catch basin on the west side of the former clarifier to replace the one removed during excavation,and connecting the catch basin to the truncated 4-inch diameter sewer line on the east side of the former clarifier. The catch basin was sealed at its base with concrete,which was allowed to set for several days prior to completing the backfilling of the excavation with additional pea gravel. The ground surface was restored with additional concrete poured by Del-Tech. Attachment 3 10759-EXC SUMMARY LTR