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California ?gional Water Quality Cor A Board @��,P�P <br /> Central Valley Region <br /> Robert Schneider,Chair <br /> Linda S.Adams Arnold <br /> 4ecreturt.fot. Sacramento Main Office Schwarzenegger <br /> i.m ironmentul 11020 Sun Center Drive 9200.Rancho Cordova.California 95670-61 14 Governor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> hup:/hvww.waterboards.ca.gov/central alley SEC ERWED <br /> 2 August 2006 AIIG 0 4 2006 <br /> ENVIRONMENT HEALTH <br /> Mr. Jeff Whitworth <br /> PERMIT/SERVICES <br /> Shell Oil Products US <br /> 20945 S. Wilmington Avenue <br /> Carson, CA 90810 <br /> APPROVAL OF INVESTIGATION WORK PLAN, FORMER SHELL CENTRAL VALLEY <br /> CRUDE OIL PIPELINES, HANSEN ROAD NEAR SCHULTE ROAD, TRACY, SAN JOAQUIN <br /> COUNTY <br /> Staff of the California Regional Water Quality Control Board, Central Valley Region (Regional <br /> Water Board) has reviewed the 26 June 2006 Investigation Work Plan, Former Shell Central <br /> Valley Crude Oil Pipelines, Cordes Ranch, Hansen Road near Schulte Road, Tracy (Work <br /> Plan) submitted by Science Applications International Corporation (SAIC) on behalf of Shell <br /> Oil Products US (Shell). The Work Plan was submitted in response to a meeting between <br /> Regional Water Board staff and Shell representatives on 16 November 2005. The Work Plan <br /> proposes further investigation of the nature of petroleum hydrocarbons dissolved in <br /> groundwater through vertical profiling in the vicinity of the former crude oil pipelines. In <br /> addition, Shell proposes to collect soil vapor samples to evaluate the potential threat to indoor <br /> air quality of future developments and soil samples for leachability testing to evaluate the <br /> potential threat to groundwater quality from existing contaminants. The findings will be <br /> summarized in a written report that will include recommendations for additional work with <br /> respect to groundwater, if warranted. <br /> Shell proposes to collect soil vapor samples from four locations and soil samples for <br /> leachablility testing from three locations beneath the former pipeline. A cone penetrometer rig <br /> will be used to advance the borings and samples will be collected through downhole <br /> equipment. Soil vapor samples would be collected at 6 feet, 16 feet, and 30 feet depth at <br /> each location in accordance with California EPA's Advisory— Active Soil Gas Investigations <br /> and Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air. <br /> Purge volume testing will be utilized to evaluate the optimum purge volume for sample <br /> collection. The samples will be collected in Summa canisters and analyzed for volatile organic <br /> compounds (VOCs) using EPA Method TO-15. <br /> Groundwater samples will be collected from two locations northeast of the pipeline in the <br /> inferred hydraulically downgradient direction where previous deep borings have been <br /> completed. Groundwater samples will be collected 100 feet northeast of the former pipeline at <br /> 20-foot depth intervals between approximately 40 feet depth and 150 feet depth using discrete <br /> interval sampling equipment. Total Petroleum Hydrocarbons in the diesel (TPHd) and crude <br /> California Environmental Protection Agency <br /> �d Rec)r(ed Poper <br />