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California Vional Water Quality Contl Board 0.01-11 <br /> Central Valley Region <br /> Karl E. Longley,SeD, P.E.,Chair. <br /> Arnold <br /> Linda S. Adams 11020 Sun Center Drive 9200,Rancho Cordova,California 95670-6114 Schwarzenegger <br /> Secretan for phone(916)464-3291 •FAX(916)464-4645 Governor <br /> Environmental httP flvmw waterboards.ca.gov/centralvallev _ (❑; /; _ <br /> ProtectionI!/��E" II`,// f- 1 <br /> 10 October 2008 OCT 1 5 2008 J <br /> ENVIRONMENT HEALTH <br /> Mr. Jeff Goold PERMIT/SERVICES <br /> Shell Oil Products US <br /> 20945 South Wilmington Avenue <br /> Carson, CA 90810 <br /> SITE INVESTIGATION, SOIL VAPOR SAMPLING, AND DUAL-PHASE EXTRACTION <br /> PILOT TEST, SHELL STOCKTON TERMINAL, 3515 NAVY DRIVE, STOCKTON, SAN <br /> .iOAQUIN COUNTY <br /> Regional Water Quality Control Board, Central Valley Region (Regional Water Board) staff <br /> reviewed the following reports: <br /> 26 September 2008 Site Investigation Report (Investigation Report) <br /> 26 September 2008 Soil Vapor Sampling Report (Soil Vapor Report) <br /> 30 September 2008 Dual-Phase Extraction Pilot Test Report (Pilot Test Report) <br /> Conestoga-Rovers and Associates (CRA) submitted these reports on behalf of Shell Oil <br /> Products US (Shell) for Shell's Stockton Terminal at 3515 Navy Drive in Stockton (Site). <br /> Shell proposed the site investigation in the 15 January 2008 Site Investigation Work Plan <br /> Addendum. The Investigation Report describes the results of sampling from six soil borings <br /> (SB-22 through SB-27) advanced to depths ranging from 79 to 90 feet below ground surface <br /> (bgs). The objective of the investigation was to assess petroleum hydrocarbon concentrations <br /> in soil and groundwater and to delineate the vertical extent of the plume downgradient of the <br /> Site. <br /> SB-22 through SB-24 were advanced in the three source areas surrounding monitoring wells <br /> MW-10, N!%N-13R and MW-20. Shell calls these areas "hot spots". The three borings were <br /> logged in the field using electronic data generated by a cone penetrometer (CPT) equipped <br /> with a membrane interface probe (MIP). Confirmation soil and groundwater samples were <br /> collected for laboratory analysis. <br /> The CPT lithologic logs show that the site is generally underlain by interbedded clay and silty <br /> clay. The CPT data show that subsurface units become progressively sandier in the southern <br /> portion of the Site. Discontinuous sand lenses were logged at depths of 25 and 60 feet bgs in <br /> the central and southern portion of the Site. A laterally continuous sand layer is present at <br /> 70 bgs. Laboratory analytical results of the soil samples collected between the surface and <br /> 20 feet bgs showed that the highest concentrations of total petroleum hydrocarbons as <br /> gasoline (TPHg) and TPH as diesel (TPHd) were encountered at about 10 feet bgs in each <br /> boring. The maximum concentrations of TPHg and TPHd were in SB-24 (hot spot MW13R) at <br /> California Environmental Protection Agency <br /> ped Recycled Paper <br />