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SUPPLEMENTAL SITE INVESTIGATION WORK PLAN <br /> South Pointe Property <br /> Stockton, California <br /> Scope of Work <br /> to 20%) of primary samples will be analyzed for these constituents, as well as for chromium. <br /> Considerations given to this secondary analytical program per previous comments from DTSC <br /> are summarized below. <br /> - Because VOCs in shallow soil may have undergone volatilization due to solar and <br /> atmospheric exposure, samples for analysis of VOCs will be collected from a depth of at <br /> least 3.5 ft bgs. A subset of shallow (less than 3.5 ft) VOC samples will be collected from <br /> the 3,000 cy soil pile for characterization purposes. <br /> - Although historical assessment suggests that chromium is not a primary site-related COC, <br /> chromium has been added as an additional compound to assess the potential for <br /> hexavalent chromium to be present in site soils, as historical operations referenced the <br /> use of boilers, which may have used descaling compounds containing hexavalent <br /> chromium. Samples from boreholes 35 and 36, advanced in the vicinity of the historical <br /> boiler, will also be analyzed for chromium. Samples reporting the two highest and two <br /> lowest concentrations of chromium will be additionally analyzed for hexavalent <br /> chromium.This approach should allow for assessment of hexavalent chromium across a <br /> range of total chromium concentrations. <br /> - Samples for analysis of PAHs, PCBs, and chromium will be collected from surface or near- <br /> surface soils. <br /> - The highest historical detection of PCBs at the site was 66 mg/kg at location PL-9 at 3 ft <br /> bgs. To assess the extent of PCBs at this location, Stantec proposes advancing boreholes <br /> 27a, 27b, and 27c at locations around historical location PL-9. Soil samples will be <br /> retained from the ground surface and from 3 ft bgs and analyzed for PCBs. <br /> - The McCormick and Baxter Superfund site is located approximately 2,000 feet southwest <br /> of the site. Based on historical data, site-related COCs included pentachlorophenol <br /> (PCP), an herbicide used as a wood preservative.To asses the potential for PCP to be <br /> present at the site, samples collected from ground surface and 4 ft bgs at boreholes 32, <br /> 36, 38, and 40 will be analyzed for PCP. These boreholes are located along the <br /> southwestern edge of the site, closest in distance to the McCormick and Baxter site. <br /> Tables 1 and 2 summarize the soil sampling program. <br /> 4.1.2 Groundwater Assessment <br /> Four boreholes (2, 7, 28, and 33) will be advanced to first-encountered groundwater to assess <br /> potential groundwater impacts from site-related COCs. Groundwater samples will be analyzed <br /> for dissolved lead, cobalt, mercury, and chromium; and for OCPs, PAHs, VOCs, and PCBs. Grab <br /> groundwater samples will be analyzed for additional compounds as follows. <br /> Because historical data indicates the presence of residual concentrations of petroleum <br /> hydrocarbons in groundwater sourced from the upgradient L&M Operable Unit site, grab <br /> 4.2 <br />