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-104 Californiaoegional Water Quality Cor :)1 Board �' �, <br /> Central Valley Region <br /> %,, r <br /> Robert Schneider,Chair `°°�-^moi' <br /> Linda S.Adams Arnold <br /> S'ecretar�jor Sacramento Main Office Schwarzenegger <br /> Environmental 11020 Stn Center[rive 4200.Rancho Cordova.California 95670-6114 Governor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> http://www.waterboards.ca.gov/centralvalley <br /> 2 October 2006 U ECC `' ED <br /> Mr. Joe Aldridge, Remediation Manager OCT 5 2006 <br /> Valero, L.P. ENVIRONMENT HEALTH <br /> 685 W. Third Street PERMIT/SEMACES <br /> Hanford, CA 93230 <br /> REVIEW OF FIRST QUARTER 2006 AND SECOND QUARTER 2006 GROUNDWATER <br /> MONITORING REPORTS, ST SERVICES STOCKTON TERMINAL, 2940 NAVY DRIVE, <br /> STOCKTON, SAN JOAQUIN COUNTY <br /> Staff of the Regional Water Quality Control Board - Central Valley Region (Regional Water <br /> Board) has reviewed the 26 April 2006 Groundwater Monitoring Report, First Quarter 2006 <br /> (First QMR) and the 28 July 2006 Groundwater Monitoring Report, Second Quarter 2006 <br /> (Second QMR) submitted by Ash Creek Associates, Inc. (Ash Creek) on behalf of ST <br /> Services, L.L.C. (ST Services dba Valero, L.P. [Valero]) for the ST Services Stockton Terminal <br /> located at 2940 Navy Drive in Stockton (site). The First and Second QMRs describe <br /> groundwater monitoring activities conducted during the first quarter and second quarter 2006, <br /> respectively. Regional Water Board staff has no specific comments on the findings presented <br /> in the reports. <br /> In accordance with Monitoring and Reporting Program (MRP) No. R5-2004-0822, Valero in the <br /> First QMR requests elimination of several downgradient monitoring wells from the monitoring <br /> program based on stable to declining groundwater contaminant concentrations. Wells OW- <br /> ED, OW-7A, OW-713, OW-7C, OW-8A, OW-86, OW-8C, and OW-8D have been sampled <br /> semiannually since the third quarter 2004 and are proposed for removal from the MRP. Each <br /> of these wells with the exception of well OW-6D is a candidate for removal from the MRP. <br /> According to the MRP, well OW-6D should be sampled annually once a new well is installed <br /> between this well and the ST Services tank farm. Valero is installing a well in this area in <br /> September 2006 in accordance with the 14 April 2006 groundwater characterization work plan. <br /> Regional Water Board staff concurs with the elimination of wells OW-7A, OW-713, OW-7C, <br /> OW-8A, OW-813, and OW-8D from the MRP. Well OW-8C has shown increasing <br /> concentrations of Total Petroleum Hydrocarbons as diesel (TPHd) and benzene over the <br /> previous two sampling events, though the overall trend for benzene has been declining since <br /> the third quarter 2004. The Regional Water Board requests that well OW-8C be sampled <br /> semiannually for two more sampling events to evaluate whether the concentration trend over <br /> this period is stable to decreasing before reconsidering this well for removal from the MRP. <br /> The next quarterly groundwater monitoring report for the third quarter 2006 is due to this office <br /> by 1 November 2006. <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />