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will be placed atop the sand pack and the remainder of the borehole will be backfilled with hydrated <br /> bentonite to the ground surface to form a seal. The sampling end of the tubing will be fitted with a <br /> valve for sampling. The final screening depth at each borehole will be adjusted based on the <br /> encountered lithology. In general, probes will be screened within coarser-grained materials and <br /> clayey/saturated intervals will be avoided, if possible; <br /> • Soil gas samples will be collected in general accordance with the July 2015 DTSC and Los Angeles <br /> RWQCB "Advisory — Active Soil Gas Investigations." Each probe will be allowed to equilibrate for a <br /> minimum of two hours after installation prior to sampling. After equilibration, the sample tubing and <br /> sampler screen were purged of ambient air and Partner will collect soil gas samples for laboratory <br /> analysis using laboratory-provided, batch-certified SUMMA canisters and flow controllers with a 5- to <br /> 10-minute sample period.A tracer compound [1,1-diflouroethane(1,1-DFA)]will be placed around each <br /> probe at the ground surface while sampling to detect ambient air intrusion. Each soil gas sample (up to <br /> four soil gas samples total) will be analyzed for VOCs via EPA Method TO-15; <br /> • After sampling activities, bentonite and sand pack along with the soil gas probe equipment will be <br /> removed from the borings and the borings will be backfilled per SJCEHD requirements and capped with <br /> concrete in improved areas; <br /> • Data will be compared to applicable screening criteria and a report will be prepared summarizing the <br /> field activities, methods, and findings; and <br /> • Submit the pertinent data to the SJCEHD for review. <br /> Signatures of Environmental Professionals <br /> If you have any questions regarding this Phase II Subsurface Investigation Work Plan, please do not hesitate <br /> to contact Michel Helou at (774) 414-3666 or Joe Mangine at (510)431-6263. <br /> Sincerely, <br /> Michel Helou qSenr <br /> gine, PG <br /> Project Manager roject Manager <br /> Attachments: 1. Proposed Sample Location Map <br /> Page 4 PARTNER <br />