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California "l-gional Water Quality Conl Board <br /> Central Valley Region �I <br /> Karl E. Longley,ScD,P.E.,Chair. Arnold <br /> Linda S.Adams 11020 Sun Center Drive#200,Rancho Cordova,California 956746114 Schwarzenegger <br /> Secretaryfor Phone(916)464-3291 -FAX(916)464-4645 Governor <br /> Environmental http://www.waterboards.ca.gov/centralvalley O E� n r_> >fl _, _ <br /> Protection <br /> 10 June 2009 JUN 1 1 2009 <br /> ENVfRPP,',�,fEn!r IaGgLTN <br /> Ms. Carol Campagna PE4Po4i ;SL!qViLES <br /> Shell Oil Products US <br /> 20945 South Wilmington Avenue <br /> Carson, CA 90810 <br /> WORK PLAN TO MONITOR BASELINE CONCENTRATIONS AND RESPONSE TO <br /> INFILTRATION STUDY WORK PLAN, SHELL STOCKTON TERMINAL, 3515 NAVY DRIVE, <br /> STOCKTON, SAN JOAQUIN COUNTY <br /> Regional Water Quality Control Board, Central Valley Region (Central Valley Water Board) <br /> staff reviewed the 30 April 2009 Work Plan to Monitor Baseline Concentrations and Response <br /> to Infiltration Study Work Plan (Response) submitted by Conestoga-Rovers and Associates <br /> (CRA) on behalf of Shell Oil Products US (Shell) for the Shell Stockton Terminal at 3515 Navy <br /> Drive in Stockton (Site). <br /> Central Valley Water Board staff requested the Response in our 27 March 2009 letter. Shell is <br /> willing to conduct baseline sampling and flow modeling to determine suitable discharge limits <br /> and extraction and injection rates to re-inject treated groundwater under site-specific waste <br /> discharge requirements (WDRs). The Response proposes to conduct baseline monitoring in <br /> two downgradient wells (MW-25 and MW-26), three intraplume wells (MW-13R, MW-20, and <br /> MW-39), and two upgradient wells (MW-19 and MW-31). <br /> Of the treatment options discussed in the 13 February 2009 Remediation System <br /> Implementation Timeline and Air Sparge/Soil Vapor Extraction Pilot Test Work Plan (Report), <br /> Shell has chosen dual phase extraction with re-injection of the effluent. Shell is proposing to <br /> use historical and future groundwater data from the downgradient and upgradient wells to <br /> establish and update background groundwater concentrations. Shell also proposes to update <br /> background concentrations based on monitoring data collected from the intraplume wells as <br /> groundwater conditions respond to the re-injection of treated groundwater. <br /> Shell has calculated that re-injection of the treated groundwater could be accomplished at a <br /> rate of 40 gallons per minute (gpm) using 21 injection wells. CRA is also proposing to perform <br /> numerical modeling to evaluate hydraulic control issues that may occur in response to re- <br /> injection. Shell is also proposing to defer preparation of a work plan for land disposal, the <br /> alternative option for discharging the treated effluent, until an assessment of the feasibility of <br /> re-injection can be completed. If the numerical modeling shows that re-injection is infeasible, <br /> CRA will include an infiltration study work plan with the modeling results. <br /> Our comments are presented below. <br /> 1. We concur with the list of analytes and the monitoring frequency proposed for background <br /> sampling. <br /> California Environmental Protection Agency <br /> (d Recycled Paper <br />