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Stantec 1.00 PHASE If ENVIRONMENTAL SITE ASSESSMENT REPORT Laboratory Analytical Results and Screening March 31,2011 CAM 17 Metals: The CAM 17 metal results for the soil samples are reported in Table 4. As part of the soil vapor investigation 3 soil samples were analyzed for CAM 17 metals out of the 6 soil samples collected. The CAM 17 metal results were not detected above the laboratory MDLs for silver and thallium and low detections on the remaining metals except for arsenic. The MDL reporting limits and the low detections (except for arsenic) were approximately one order of magnitude or more below the USEPA RSLs for shallow industrial soil, the RWQCB ESLs for shallow soils (<3 meters bgs) where groundwater is a current or a potential source of drinking water, and the CHHSLs for soil in commercial/industrial land use only. The analytical results referenced above were found to contain concentrations of arsenic above the commercial/industrial land use CHHSL screening level of 0.24 mg/kg and the RSL and ESL screening level of 1.6 mg/kg. Arsenic levels are strongly influenced by the geology of the rocks from which the soils are derived, which can often result in background concentrations above the CHHSLs, RSLs, and ESLs. The DTSC and the San Francisco Bay RWQCB ESLs have acknowledged that background concentrations of several metals, including arsenic, frequently exceed health-based, direct-exposure screening goals. For this reason, Cal-EPA provides guidance for substituting background concentrations of arsenic in place of health-based screening levels. Although no Site-specific arsenic background data was available for comparison, arsenic concentrations detected in subject property soils ranged from 1.7 to 3.2 mg/kg are within the range of arsenic background concentrations of 0.6 mg/kg to 11 mg/kg cited in the University of California Kearney Foundation of Soil Science report entitled 'Background Concentrations of Trace and Major Elements in California Soils," dated March 1996. Accordingly, arsenic concentrations detected in the soil samples from the Site are judged to be indicative of natural background conditions. A summary of the analytical results including the CHHSL, ESL, and RSL screening levels are included on Table 4. 3.3 INVESTIGATION-DERIVED WASTE ANALYTICAL RESULTS Soil cuttings and decontamination fluids generated during the field activities were placed into DOT-approved 55-gallon drums, segregated by matrix (solid/liquid), and labeled for disposal. The drums were labeled with Stantec's contact information clearly displayed. Waste disposal services will be subcontracted to Advanced Chemical Transport of Merced, California. The analytical results for the investigation-derived waste are summarized in Tables 5 through 12. A letter summarizing the disposal of the investigation derived waste will be addressed under a separate cover. The waste manifest documentation will be forwarded to Calpine upon receipt. i:\projects\calpine\lodi\reportUodi.svrpt.do" 3.3