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Californir "egional Water Quality Co Mol Board <br /> Central Valley Region <br /> Karl E. Longlev,ScD P.E. Chair <br /> I.inrl❑ �. \darns Arnold <br /> Sacramento Main Office SchwarzenegKer <br /> " <br /> 11020 Sun Center Drive 11200,Rancho Cordo+a.California 95670-6114 <br /> {'hone(916)464-3291 •FAX(916)464-4645 Goveriwr <br /> http./hv+vw+vaterboards.ca.gov/centralvallev <br /> I <br /> 8 May 2007 RA <br /> ESV/k ., ,�_ <br /> UrY <br /> Mr Jeff Whitworth PERM/l/S R j�FSTh <br /> Shell Oil Products US <br /> 20945 S. Wilmington Avenue <br /> Carson, CA 90810 <br /> REVIEW OF SOIL REMEDIAL ACTION REPORT, 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 13 March 2007 Remedial Action Report, Mountain House <br /> Neighborhood C and D (RAR) submitted by Science Applications International Corporation <br /> (SAIC) on behalf of Shell Oil Products US (Shell). The RAR was submitted to document <br /> remedial soil excavation and soil gas sampling activities at the former location of Shell crude <br /> oil pipelines within the Mountain House residential development in Tracy. The Department of <br /> Toxic Substances Control, Schools Division (DTSC) provided review comments for a portion of <br /> Neighborhood D where construction of Mountain House High School is planned. <br /> Soil impacted with petroleum hydrocarbons was excavated from two areas in Neighborhood C <br /> and eleven areas in Neighborhood D. The excavations ranged from 10 feet to about 26 feet <br /> below ground surface (bgs), the approximate depth of the water table. Soil was removed that <br /> was impacted by separate phase hydrocarbons (SPH), as evidenced by visual staining, or that <br /> ::xceeded a concentration of 5,000 milligrams per kilogram (mg/kg) Total Petroleum <br /> Hydrocarbons as crude oil (TPHcr), a remedial excavation goal provided by Regional Water <br /> Board staff. Approximately 130,00 cubic yards of soil were removed from the site and <br /> transported to Altamont Landfill in Altamont for disposal. <br /> Confirmation soil samples were collected from the base and sidewalls of the excavations to <br /> document petroleum hydrocarbon concentrations remaining in place. Soil samples were <br /> analyzed for TPHcr and TPH as diesel (TPHd) using EPA Method 8015B, and benzene, <br /> toluene, ethylbenzene, and xylenes (BTEX) using EPA Method 8260B. Residual TPHcr and <br /> TPHd were reported at maximum concentrations of 5,100 mg/kg and 3,400 mg/kg, <br /> respectively, in soil at Area 11 (sample EX17-18-B59 collected at 23 ft bgs near the water <br /> table); however, the majority of the confirmation samples were non-detect for TPH with very <br /> few approaching 5,000 mg/kg TPHcr. BTEX compounds were not detected at concentrations <br /> greater than their respective reporting limits. The remedial excavations were backfilled to the <br /> pre-existing grade with soil segregated during excavation and soil imported from other areas of <br /> the site. Soil backfill was analyzed for TPHcr, TPHd, and BTEX at a frequency of one sample <br /> California Environmental Protection Agency <br /> �a Rec.vcled Paper <br />