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Fortner Discovery Chevrolet September 16, 1998 Tracy,California Re Dorton Remedial Work The two groundwater samples were prepared and chilled for transport p under chain-of- custody (COC) on the sampling date-of-collection and sent to Kiff Analytical in Davis, California (Certification No. 2236). The requested analyses were TPHg using EPA Method 8015 (modified) and the volatile aromatics BTEX using EPA Method 8020. The laboratory water results are summarized in Table 2. The groundwater sample collected prior to treatment(W-0819-Tank) indicated detectable concentrations of TPHg (of 530 parts per billion [ppb]) and BTEX (between 0.83 ppb and 64 ppb). The groundwater sample collected after treatment (W-0821-HT) indicated no detectable concentrations of TPHg (less than 50 ppb) and BTEX (less than 0.5 ppb). Copies of the laboratory and COC reports are included in Attachment C. On August 27, permission to discharge treated groundwater was acquired from the City of Tracy Utilities Department. After receiving approval for discharge, the treated S , groundwater was then discharged into the City of Tracy sanitary sewer system on August 28 and 31, and September 1. A flow meter attached to the effluent discharge hose indicated a total of 5,750 gallons of treated effluent water was discharged into the sanitary sewer system. Copies of the City of Tracy discharge approval letters are included in Attachment A. GroundwaterVerification Monitoring .,. onng On August 31, a post-excavation groundwater sample (W-0831-MW2) was collected from well MW-2, which is located immediately north of the excavation area (Figure 3). The • groundwater sample was prepared and chilled for transport under-chain-of-custody (COC) on the sampling date-of-collection and sent to Kiff Analytical in Davis, California. The requested analyses were: TPHg using EPA Method 8015 (modified) and the volatile aromatics BTEX using EPA Method 8020. I � On September 2, Kiff Analytical reported the analytical results for the MW-2 groundwater r sample. The groundwater sample indicated detectable concentrations of TPHg (of 260 ppb) L and BTEX (between 0.97 ppb and 46 ppb). The laboratory water results are summarized in Table 2. Copies of the laboratory and COC reports are included in Attachment C. Conclusions As indicated on the Excavation Plan, the final dimensions of the excavation were approximately 32 feet wide by 40 feet long by 12 feet deep. The excavated soil was predominantly hydrocarbon-impacted soil within the 1,000 ppm TPHg, 100 ppm TPHg, and 5 ppm Benzene isoconcentration contours, as depicted in the Problem Assessment Report (Horizon, March 20, 1998) and the Corrective Action Plan (Horizon, June 5, 1998). As proposed in the Corrective Action Plan and approved by the SJCPHS-EHD, the Target Cleanup Level for the site was 5 ppm Benzene in soil. The laboratory results of the five soil samples collected from the sidewalls and floor of the excavation indicate that the Target Cleanup Level for the site was achieved for the site. 3001-21.ovx 5 HORIZON ENVIRONMENTAL INC.