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California&gional Water Quality CoW Board _ <br /> Central Valley Region 9 <br /> Linda S.Adams Arnold <br /> .S'ecremp�/or Sacramento Main Office Schwarzenegger <br /> Environmental 11020 Sun Center Drive 4200.Rancho Cordova.California 9567P6114 Governor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> http://www.waterboards.ca.gov/centralvalley n� <br /> )ppUlll1 �����D <br /> 4 December 2006 DEC 0 S 2006 <br /> ENVIRONMENT HEALTH <br /> PERMIT/SERVICES <br /> Mr. Jeff Whitworth <br /> Shell Oil Products US <br /> 20945 South Wilmington Avenue <br /> Carson, CA 90810 <br /> REVIEW OF REVISED 2006 FIRST SEMIANNUAL REPORT, SHELL STOCKTON <br /> TERMINAL, 3515 NAVY DRIVE, STOCKTON, SAN JOAQUIN COUNTY <br /> Staff of the Regional Water Quality Control Board, Central Valley Region (Regional Water <br /> Board) has reviewed the 27 October 2006 Revised Groundwater Monitoring and Remediation <br /> Report, 2006 Semi-Annual Report— 1St and 2"d Quarters (Revised First Semiannual Report) <br /> submitted by Cambria Environmental Technology, Inc. (Cambria) on behalf of Shell Oil <br /> Products US (Shell) for the Shell Stockton terminal located at 3515 Navy Drive in Stockton <br /> (site). The Revised First Semiannual Report was submitted in response to the Regional Water <br /> Board's letter dated 2 October 2006 that requested a revised report to include items required <br /> by Monitoring and Reporting Program (MRP) No. R5-2005-0810. <br /> The Revised First Semiannual Report included a revised site location map, and <br /> isoconcentration contour maps for dissolved Total Petroleum Hydrocarbons (TPH) as <br /> gasoline, TPH as diesel, benzene, and methyl tertiary butyl ether (MTBE). Discussions of <br /> groundwater chemical concentration trends, plume stability, and operation of the existing <br /> groundwater extraction system were also provided. Monitored natural attenuation (MNA) was <br /> recommended as the preferred remedial approach to address groundwater pollution at the <br /> site. <br /> The source area wells are MW-1 near the loading rack and MW-10 in the aboveground tank <br /> storage area. Separate phase hydrocarbons (SPH) were observed at a thickness of 0.05 foot <br /> in well MW-1 in May 2006 though were not found in August 2006. The groundwater plumes <br /> appear to be relatively stable in lateral extent; however, chemical concentrations in several <br /> plume interior wells show increasing trends. <br /> REGIONAL WATER BOARD REVIEW COMMENTS <br /> A temporary groundwater extraction (GWE) system has been operational at the site since April <br /> 2006. Groundwater is being pumped from one well (MW-1) at a rate of approximately 0.2 <br /> gallon per minute (gpm). The extracted water is collected in a temporary storage tank before <br /> being transported offsite to Shell's Martinez Refinery for recycling. The GWE system appears <br /> California Environmental Protection Agency <br /> pia Recycled Paper <br />