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Q <br /> Limited Phase 11 Subsurface Investigation Report <br /> Property Lease Port of Stockton <br /> Stockton,California a ntea g ro u p <br /> Antea Group Project No. UPR8298B <br /> silver, vanadium, and zinc) in soil samples collected as part of this investigation. The laboratory reported one <br /> metal (arsenic) detected above the Direct Exposure SSL at a concentration of 11 milligrams per kilogram (mg/kg) in <br /> B-22. Table 1B includes a summary of the total metal analytical data and provides a comparison of detections to <br /> SSLs and background reference concentrations. Selenium was not reported above the LRL in any of the soil <br /> samples. <br /> To adequately evaluate the metals detected in shallow soil, Antea Group compared the laboratory data to typical <br /> naturally occurring concentrations in regional soil, or "background" concentrations. Each metal concentration <br /> listed in Table 1B was compared to published background data for California soils. The background metals <br /> concentrations used for comparison are the averages listed in a 1996 report that established a database for 46 <br /> trace and major naturally occurring elements found in 50 benchmark soil samples collected throughout the state <br /> of California (Kearney, 1996). Antea Group reviewed the data presented in the Kearney Report to evaluate site- <br /> specific background trends and to note exceedances of typical background levels. For arsenic, the Kearney report <br /> lists a concentration average of 3.5 mg/kg and maximum of 11 mg/kg. Upon comparing the published benchmark <br /> concentrations with the current laboratory results, Antea Group determined that the metals concentrations <br /> reported during this investigation are within typical background concentration ranges and/or below the RWQCB <br /> SSL. <br /> 4.3 Polychlorinated Biphenyls (PCBs) <br /> Antea Group requested PCBs analysis for 28 of the 41 submitted soil samples. Of the samples submitted, only one <br /> concentration (B-17 at 1.5-2.0 feet bgs)exceeded the LRL at 0.069 mg/kg. This concentration is less than the SSL of <br /> 2.7 mg/kg. Table 1A includes a summary of the analytical data for PCBs. <br /> 4.4 Pesticides <br /> The laboratory analyzed a total of 17 soil samples for pesticides. Of the samples submitted, only four soil samples <br /> (B-7, B-11, and B-27 at 1.5-2.0 feet bgs, and B-14 at 5.5-6.0 feet bgs) had concentrations detected above the <br /> respective LRLs; however, all of the concentrations were below the respective established SSLs. Table 1A includes <br /> a summary of the analytical data for pesticides. <br /> 4.5 Quality Assurance/Quality Control (QA/QC) <br /> QA/QC measures included laboratory method blanks and quality control (QC)samples and a QA/QC data validation <br /> check conducted by Conestoga-Rovers and Associates (CRA) on the laboratory's analytical results for the samples <br /> collected on April 15 and 16, 2014. The laboratory report and CRA validation memo is included as Appendix C. <br /> The table presented below provides a summary of QA/QC information. <br /> 6 www.anteagroup.com <br />