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California I0ional Water Quality Contr*Board "®R; <br /> (\- Central Valley Region <br /> vKarl E.Longley,ScD,P.E.,Chair. <br /> Linda S.Adams Arnold <br /> Secretaryfor Sacramento Main Office Schwarzenegger <br /> Environmental 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Govemor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> http://w .waiLerbouds.ca.gov/centralvalle� <br /> 14 September 2007 SEP 2 1 2007 <br /> EI`l0:jNMEN1`HEALTH <br /> Mr. Jeff Whitworth E.dnl•!� 11� <br /> Shell Oil Products US <br /> 20945 South Wilmington Avenue <br /> Carson, CA 90810 <br /> SOIL VAPOR SAMPLING WORK PLAN, SHELL STOCKTON TERMINAL, 3515 NAVY <br /> DRIVE, STOCKTON, SAN JOAQUIN COUNTY <br /> Regional Water Quality Control Board, Central Valley Region (Regional Water Board) staff <br /> reviewed the 17 August 2007 Soil Vapor Sampling Work Plan (Work Plan) submitted by <br /> Conestoga-Rovers and Associates (CRA) on behalf of Shell Oil Products US (Shell) for the <br /> Shell Stockton terminal located at 3515 Navy Drive in Stockton (Site). <br /> The Work Plan describes a soil vapor sampling investigation to obtain data for the proposed <br /> human health risk assessment (HHRA). The Work Plan proposes to advance two soil borings <br /> (SB20 and SB21) and 10 dual-completion soil vapor sampling points (V-1 through V-10). Soil <br /> and soil vapor samples will be collected and analyzed to assess the potential for vapor <br /> intrusion into indoor air at the commercial buildings located at the Site. Shell proposes to <br /> advance the soil borings at two source areas (SAs), SA-1 and SA-2, to install the soil vapor <br /> probes in the vicinity of the office-warehouse and garage. <br /> Shell proposes to collect soil samples from 3, 5 and about 10 feet bgs from SB20 and SB21, <br /> depending on the depth to the groundwater table. Soil samples will also be collected from 0.5 <br /> and 4.5 feet bgs from V-1 through V-10. The dual-completion soil vapor probes will be <br /> screened at 4 and 8 feet bgs at the office-warehouse, and at 3 and 6 feet at the garage. <br /> Ambient air samples will be collected adjacent to the soil vapor samples. All samples will be <br /> analyzed for TPHg, TPHd, BTEX, and fuel oxygenates. Soil vapor samples will also be <br /> analyzed for oxygen, carbon dioxide, nitrogen, and methane. Soil data will be compared to the <br /> San Francisco Bay Regional Water Board's (Region 2) environmental screening levels (ESLs). <br /> Soil gas analytical results will be compared to California Human Health Screening Levels <br /> (CHHSLs) published by the Office of Environmental Health Hazard Assessment (OEHHA). <br /> Our comment on the Work Plan is presented below. <br /> 1. Regional Water Board staff concurs with the Work Plan. However, comparison of the soil <br /> data to the Region 2 ESLs and soil gas data to OEHHA's CHHSLs will only provide an <br /> indication of whether additional investigation is warranted. Since this Site is an industrial <br /> work place, risk evaluation for the workers is regulated by the Occupational Safety and <br /> Health Administration's (OSHA) exposure limits. Therefore, if the comparisons to the <br /> California Environmental Protection Agency <br /> 0 Recycled Paper <br />