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Californieegional Water Quality Cool Board <br /> Central Valley Region r r <br /> Adams Sacramento <br /> Linda S. <br /> Sacramento Main Office Schwarzenegger <br /> Secretaryfor 11020 Sun Center Drive H200.Rancho Cordova,California 95670-6114 <br /> Environmental Phone(916)464-3291 •FAX(916)464-4645 0l Governor <br /> ��Protection http://www.waterboards.ca.gov/centralvalley <br /> Jd�,z V�D <br /> 24 January 2007 ENl//RO52007 <br /> CERTIFIED MAIL CERTIFIED MAIL PC7006 <br /> �PENTNE <br /> 7006 0810 0002 9651 0445 7006 0810 0002 9651 0 eilv?'//O��TF/ <br /> Mr. Denis Brown Mr. John Kendrick <br /> Shell Oil Products 3011 W. Benjamin Holt Drive <br /> 20945 Wilmington Ave. Stockton CA 95219 <br /> Carson CA 90810 <br /> CHANGE OF LEAD AGENCY, FILE REVIEW, AND REQUEST FOR WORK PLAN, <br /> SHELL STATION NO. 204-7524-4404, 3011 W. BENJAMIN HOLT DRIVE, STOCKTON_ <br /> SAN JOAQUIN COUNTY (REGIONAL BOARD CASE # 390557) <br /> In a letter dated 3 January 2007, San Joaquin County Environmental Health Department <br /> (SJCEHD) transferred the regulatory agency lead to the Regional Board for the cleanup of <br /> petroleum hydrocarbons at the Shell Station No. 204-7524-4404, 3011 W. Benjamin Holt <br /> Drive, Stockton (Site, Figure 1). Please address all future correspondence to the address in <br /> the header of this letter, and continue to send copies of written correspondence (excluding <br /> work plans and reports) to SJCEHD. <br /> Enclosed are: 1) the non-concurrence letter to SJCEHD from the Regional Board Executive <br /> Officer, and 2) the Regional Board staff memo, dated 13 December 2006, which provides a <br /> chronology of the Site. In preparing the memo, I conducted a preliminary case review and <br /> disagreed with the closure recommendation given by SJCEHD. Specifically, the Site <br /> characterization is incomplete for the petroleum hydrocarbon Methyl tert-Butyl Ether (MtBE) for <br /> the following reasons: <br /> • The lack of data beyond the current monitoring well network (downgradient wells are <br /> impacted by MtBE) shows the extent of the MtBE is not defined laterally in the apparent <br /> downgradient direction, which is a requirement for closure. <br /> • While MtBE concentrations onsite have declined 3 orders of magnitude since 1997, <br /> residual MtBE concentrations continue to fluctuate in the downgradient monitoring wells <br /> to levels above Water Quality Objectives (5 ug/L), which are not protective of beneficial <br /> uses of groundwater and may indicate an unstable groundwater plume with continued <br /> leaching of MtBE contamination from soil to groundwater (See Graphs in Memo). <br /> • The data show that the MtBE groundwater plume has moved under Interstate 5 and <br /> may be continuing towards sensitive receptors (irrigation wells) on the opposite (east) <br /> side of Interstate 5. <br /> In order to achieve Site closure, Shell must show declining concentration trends for all <br /> constituents, predict when Water Quality Objectives will be met, and determine the <br /> California Environmental Protection Agency <br /> pia Recycled Paper <br />