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Jeff Whitworth - 2 - 25 September 2007 <br /> Indoor Air published by the Los Angeles Department of Toxic Substances Control. Vapor <br /> samples will be collected in six-liter Summa canisters after allowing 30 minutes for <br /> equilibration of subsurface conditions once the target depth is reached and the probe is <br /> retracted. A flow regulator placed between the probe and Summa canister will be operated at <br /> a flow rate not to exceed 200 milliliters per minute (ml/min). Each sample will be collected <br /> after purging of three sample train volumes. Leak detection testing for ambient air entering the <br /> sampling system will be performed using a leak check compound such as tetrafluoroethane. <br /> The vapor samples will be transported to a fixed laboratory and analyzed for BTEX, <br /> naphthalene, and tetrafluoroethane according to EPA Method TO-15. <br /> Shell will prepare a report describing the field investigation results and comparing the data to <br /> California Human Health Screening Levels (CHHSLs) established by the Office of <br /> Environmental Health Hazard Assessment (OEHHA). Recommendations will be made in the <br /> report for additional site activities based on the investigation results and planned site <br /> development. <br /> Regional Water Board staff concurs with the activities proposed by Shell in the Soil Vapor <br /> Work Plan. Please provide a schedule for fieldwork completion and report submittal before <br /> commencing the investigation. <br /> If you have any questions regarding this letter, you may contact me at (916) 464-4719 or <br /> mclardy@waterboards.ca.gov. <br /> 1w'(t1 ! <br /> Mark W. Clardy, P.G. <br /> Engineering Geologist <br /> Private Sites Cleanup Unit <br /> cc: Mr. Michael Hurd, Scientific Applications International Corporation, Oakland <br /> Mr. Mike Infurna, San Joaquin County Environmental Health Department, Stockton <br /> Ms. Eileen Nottoli, Allen Matkins Leck Gamble & Mallory LLP, San Francisco <br /> Mr. Manuel Oliveira, Escalon <br /> Mr. Joseph Rivani, Global Investment & Development LLC, Los Angeles <br /> Ms. Joanne Kimbrough, 17529 West Grant Line Road, Tracy, CA 95376 <br /> Mr. Nader Shareghi, Mountain House Community Services District, Stockton <br /> Mr. David Wood, Apeira, 3282 East Highway 4, Murphys, CA 95247 <br /> MWC/W:\slic_dodWustinStaff\Mark\Shell Mtn.House Pipeline Tracy\8-15-07 Shell Mtn House B soil gas WP.doc <br />