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Californi 'Zegional Water Quality C( rol Board <br /> Central Valley RegionQW; 04."r-0,Kathrin Hart, Chair <br /> Linda S.Adams Arnold <br /> Secrelan Jor <br /> 11020 Sun Center Drive X200,Rancho Cordova,California 9667461 14 Schwarzenegger <br /> Env�ronmenla/ Phone(916)464-3291 •FAX(916)464-4645 <br /> hUp:/lwww.waterboards.ca.gov/cenvalvalley � =agn(� =� Governor <br /> Proreclron iLWJ� \��(J/ i�.JJ <br /> AIJfi 3%Zi l$12010 <br /> Ms. Shelby Lathrop ENV ONM•WN f HEALTH <br /> ConocoPhillips Company pERM T/SERVICES <br /> 76 Broadway <br /> Sacramento, CA 95818 <br /> ADDENDUM TO REMEDIAL ACTION PLAN, FORMER TOSCO BULK TERMINAL #10013, <br /> 3505 NAVY DRIVE, STOCKTON, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff reviewed the 21 July 2010 .Addendum to Remedial Action Plan (RAP Addendum) <br /> submitted on behalf of the ConocoPhillips Company (ConocoPhillips) by Stantec Consulting <br /> Corporation (Stantec) for the former Tosco bulk fuel terminal at 3505 Navy Drive in Stockton <br /> (Site). ConocoPhillips conducts groundwater monitoring at the Site pursuant to Monitoring and <br /> Reporting Program No. R5-2004-0824. NuStar Energy (NuStar) currently owns and operates <br /> the terminal. <br /> The RAP Addendum was submitted in response to our 14 June 2010 letter which commented <br /> on ConocoPhillips RAP. The RAP recommended continuing the oxygen injections until the <br /> fourth quarter of 2010. If the recent concentration trends remain unchanged, the RAP proposed <br /> to initiate monitored natural attenuation (MNA) during the first quarter of 2011 until remedial <br /> objectives are met or until MNA parameters are projected to meet water quality objectives <br /> (WQOs) in a reasonable time. <br /> Our 14 June comments requested that ConocoPhillips (1) specify the remedial objectives, <br /> (2) present background concentrations on which the proposed remedial objectives are based, <br /> (3) present a contingency plan should constituents of concern (CDCs) rebound once the <br /> injections are discontinued, and (4) define the magnitude of the rebound that would trigger <br /> implementation of the contingency measures. <br /> In the RAP Addendum, ConocoPhillips postulates that groundwater at the Site is largely non- <br /> potable based on an estimated total dissolved solids (TDS) concentration of 1,500 milligrams <br /> per liter (mg/L). Based on this assumption ConocoPhillips proposes to <br /> • perform risk-based modeling to determine appropriate site specific remedial <br /> objectives/cleanup goals, <br /> • pursue low risk case closure if site CDCs are absent from background wells MW-6 and <br /> MW-10, and concentrations of "select drinking water quality constituents" listed on <br /> Page 2 of the RAP Addendum exceed State of California drinking water criteria, <br /> • discontinue oxygen injection activities at the close of 2010, and <br /> • reinstate for six months bi-weekly oxygen injections as a contingency measure, if total <br /> petroleum hydrocarbons as diesel (TPHd), TPH as gasoline (TPHg), tertiary butyl alcohol <br /> (TBA), methyl tertiary butyl ether (MTBE) or benzene rebound to five times greater than <br /> California Environmental Protection Agency <br /> Cpl Reqc•(ed Paper <br />