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Californi0egional Water Quality Co of Board <br /> Central Valley Region <br /> r <br /> Linda S. Adams Arnold <br /> SVLrenr'I /Or Sacramento Main Office Schwarzenegger <br /> wrmn <br /> Fnoenn,l 11020 Son Center Drive#200.Rancho COrdo�a.California 9567(.61 l4 Governor <br /> Prole,„on Phone(916)464-3291 •FAX(916)464-4645 <br /> http1/w,A,%%.ceaterboards.ca.gov/central alleN <br /> AE(CENEDD <br /> 13 December 2006 DEC 1 h 0006 <br /> ENVIRC(tilr. ' t; - ; rH <br /> PER[[: <br /> Mr. Jeff Whitworth ,r 5 <br /> Shell Oil Products US <br /> 20945 S. Wilmington Avenue <br /> Carson, CA 90810 <br /> REVIEW OF SOIL VAPOR SURVEY WORK PLAN, MOUNTAIN HOUSE NEIGHBORHOODS <br /> C AND D, FORMER SHELL CENTRAL VALLEY CRUDE OIL PIPELINES, TRACY, SAN <br /> JOAQUIN COUNTY <br /> Staff of the Regional Water Quality Control Board, Central Valley Region (Regional Water <br /> Board) has reviewed the 20 November 2006 Soil Vapor Sampling Work Plan, Mountain House <br /> Neighborhood C and D (Soil Vapor Work Plan) submitted by Science Applications <br /> International Corporation (SAIC) on behalf of Shell Oil Products US (Shell). The Soil Vapor <br /> Work Plan proposes the collection and analysis of soil vapor samples in remedial soil <br /> excavation areas at the former location of Shell crude oil pipelines within the Mountain House <br /> residential development in Tracy. Representatives of the Department of Toxic Substances <br /> Control (DTSC), the Regional Water Board, SAIC, Shea Homes, the developer, and their <br /> consultant, Condor Earth Technologies, Inc. discussed elements of the proposed scope of <br /> work in a meeting held on 14 November 2006. <br /> Shell proposes to collect soil vapor samples along the trace of the former crude oil pipeline to <br /> evaluate the risk of vapor migration to indoor air following site development. Soil vapor <br /> samplina is proposed at 24 locations in eight remedial soil excavation areas, designated as <br /> Areas 1, 3, 4, 5, 6 and 7, 9 and 10, 11, and 13. Areas 3, 4 and 5 are located within an area <br /> planned for high school construction. Direct push equipment will be used to advance the <br /> temporary vapor probes to the desired depth. Vapor samples will be collected within the <br /> backfilled excavations from approximately 1 foot below the base of the excavation. In <br /> addition, vertical profile vapor samples will be collected at depths of 5 feet, 10 feet, and 15 feet <br /> exterior of Areas 1, 4, 6, 8, 10, 11, and 13. If sample collection within an excavation area is <br /> not possible due to penetration refusal or high moisture content, a location exterior of the <br /> excavation will be sampled alternatively. Shell plans to collect a total of approximately 40 <br /> vapor samples. <br /> Soil vapor sampling methodology will follow guidance provided in Advisory— Active Soil Gas <br /> Investigations published by the Los Angeles Regional Water Quality Control Board and <br /> Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air <br /> published by the Los Angeles Department of Toxic Substances Control. Vapor samples will <br /> be collected in six-liter Summa canisters after allowing 30 minutes for equilibration of <br /> California Environmental Protection Agency <br /> %j Recycled Paper <br />