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BLEW <br /> ADDITIONAL INVESTIGATION <br /> Based on the analytical results for the supplemental soil vapor investigation performed in November 2025, <br /> contaminants of concern (COC) consist of ethylbenzene and xylenes (and potentially benzene due to the <br /> elevated Method Detection Limit for benzene at SVP-3). The apparent "source area" appears to be a <br /> relatively minor historical petroleum release at/near SVP-3. This release is presumed to be the result of a <br /> relatively minor surficial spill, as previous due diligence did not identify any features of environmental <br /> concern in this area of the Site (2023 Fulcrum Closure Report). <br /> The vertical and lateral extent of potential significant COC impact to soil, soil vapor and/or groundwater <br /> proximate to SVP-3 is currently unknown. Therefore, additional soil borings with soil, soil vapor and <br /> groundwater sampling are proposed to delineate the magnitude and extent of potential significant impact <br /> proximate to the "source area" at SVP-3. Additionally, based on the soil vapor results for ethylbenzene <br /> and xylenes at SVP-3, a vapor intrusion concern relative to the northern adjoining residential dwellings is <br /> unable to be ruled out. Therefore, indoor air sampling is proposed at the northern adjoining residential <br /> properties(subject to receipt of access agreements). <br /> The Work Plan includes the general rationale and procedure for advancing soil borings at the Site to collect <br /> additional soil, soil vapor and groundwater samples; and the procedure for collecting indoor air samples <br /> at the northern adjoining residential properties. Refer to Figure 1 for a depiction of proposed sample <br /> locations. <br /> PRE-FIELD ACTIVITIES <br /> Prior to proposed field activities, Blew will obtain a boring permit from the EHD. Underground utilities <br /> will be located utilizing Underground Service Alert (USA) and a private utility locator prior to <br /> commencement of field activities, including drilling into the subsurface. Prior to mobilization, Blew will <br /> prepare an Occupational Safety and Health Administration (OSHA)-compliant Site-specific health and <br /> safety plan(HASP)relative to the proposed field activities.A brief health and safety tailgate meeting will <br /> be held prior to commencing daily field activities. All proposed field activities will be performed under <br /> the supervision of a registered California Professional Geologist (PG). A licensed well driller with the <br /> State of California shall perform all drilling activities. <br /> SOIL BORINGS <br /> A total of four (4) soil borings are proposed at the locations depicted on Figure 1. Soil borings will be <br /> advanced utilizing direct-push technology. The soil borings will be advanced to a terminal depth of <br /> approximately 15 to 20 feet-bgs (based on the presumed depth to groundwater of 15 to 17 feet-bgs). <br /> B-1: Located at the location of SVP-3. Advanced to a depth of approximately 15 to 20 feet-bgs. Soil <br /> samples collected at depth intervals of 2, 5, 10 and 15 feet-bgs (deepest sample dependent on depth to <br /> groundwater). Temporary soil vapor probe installed at five feet-bgs. Low-flow groundwater sampling. <br /> Soil, soil vapor and groundwater samples analyzed for benzene, toluene, ethylbenzene and xylenes <br /> (BTEX). <br /> Work Plan for Additional Investigation <br /> 2546 French Camp Turnpike,Stockton,CA 95206 2 <br />