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California Ronal Water Quality ContreBoard <br /> 7-ON Valley Region j <br /> Karl E.Longley,SeD,P.E.,Chair. Arnold <br /> Linda S.Adams Sacramento Main Office Schwarzenegger <br /> Secretaryfor 11020 Sun Center Drive 9200,Rancho Cordova,California 95670-6114 Governor <br /> Environmental Phone(916)464-3291 •FAX(916)464-4645 <br /> Protection http://www.waterboards.ca.gov/centralvalley <br /> { 14 September 2007 <br /> L <br /> Mr. Jeff Whitworth SEPI 4007 <br /> Shell Oil Products US <br /> 20945 South Wilmington Avenue i�NVIROW�LMt#( / H <br /> Carson, CA 90810 AE) 19�1 #$ � <br /> SHELL STOCKTON TERMINAL, SITE INVESTIGATION WORK PLAN AND FEASIBILITY <br /> STUDY, 3515 NAVY DRIVE, STOCKTON, SAN JOAQUIN COUNTY <br /> Regional Water Quality Control Board, Central Valley Region (Regional Water Board) staff <br /> reviewed the 4 May 2007 Site Investigation Work Plan and Feasibility Study (WP-FS) <br /> submitted by Conestoga-Rovers and Associates (CRA) on behalf of Shell Oil Products US <br /> (Shell) for the Shell Stockton Terminal at 3515 Navy Drive in Stockton (Site). Shell conducts <br /> groundwater monitoring at the Site pursuant to Monitoring and Reporting Program (MRP) No. <br /> R5-2005-0810. <br /> Based on the August 2007 Groundwater Monitoring and Remediation Report, 2007 Semi- <br /> Annual Report (Semi-Annual Report) groundwater underneath the Site occurs in two water- <br /> bearing units. The shallow wells are screened between five and 30 feet below ground surface <br /> (bgs) and the one deep well is screened between 55 and 60 feet bgs. There is a consistent <br /> downward vertical gradient of about -0.003. Groundwater is polluted primarily with total <br /> petroleum hydrocarbons as gasoline (TPHg), TPH as diesel (TPHd), benzene, methyl tertiary <br /> butyl ether (MTBE) and tertiary butyl alcohol (TBA). The highest concentrations occur in <br /> source area wells MW-1 and MW-10, which contain up to 30,000 micrograms per liter (ug/L) of <br /> TPHg, 24,000 pg/L of TPHd, 14,000 pg/L of benzene, and 32,000 pg/L of MTBE. <br /> Shell operates a temporary groundwater extraction system (GWE) by pumping groundwater <br /> from MW-1 at an average rate of 0.45 gallons per minute (gpm). The groundwater is stored in <br /> an onsite baker tank, and vacuum trucks transport the water to Shell's Martinez refinery for <br /> recycling. Shell estimates that between January and July 2007, the GWE removed about 26 <br /> pounds of TPHg, 5 pounds of benzene, and 30 pounds of MTBE. Shell concludes that this <br /> pumping is ineffective at reducing pollutant concentrations due to the low pumping rate and <br /> low permeability conditions at the Site. <br /> Shell submitted the WP-FS in response to Regional Water Board staff's 28 February 2007 <br /> letter, which requested a feasibility study to evaluate at least three remedial alternatives and <br /> select one to remediate the groundwater underlying the Site. In the WP-FS, Shell proposes to <br /> conduct a groundwater investigation to delineate the extent of TPHd, TBA, and di-isopropyl <br /> ether (DIPE) periodically detected in deep zone monitoring well DW-2. The WP-FS proposes <br /> advancing four cone penetrometer (CPT) borings at the southwestern, offsite edge of the <br /> plume to depths of 60 to 80 feet bgs. The coarse-grained soils previously observed between <br /> 50 and 80 feet bgs will be targeted for sampling, but the actual sampling intervals will be <br /> determined in the field. <br /> California Environmental Protection Agency <br /> cd Recycled Paper <br />