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o -1)— tvv <br /> California Regional Water Quality Control Board <br />' Central Valley Region <br /> Robert Schneider Chair <br /> Tamminen Arnold Schwareenegger <br />' Secretary for Sacramento Main Office Governor <br /> Environmental Internet Address http//www swrcb ca gov/rwgcb5 R E C'� <br /> Protection 11020 Sun Center Dnve#200 Rancho Cordova,CA 95670-6114 C• ` <br /> Phone(916)464-3291 DEC 0 1 Z004 <br />' 30 November 2004 <br />' Mr John Fray Mr Jay Allen <br /> Union Oil Company of California Stone Brothers Management Company <br /> 276 Tank Farm Road 1024 W Robinhood Dr <br /> P O Box 1069 Stockton, CA 95207 <br /> San Luis Obispo, CA 93406 <br /> WORXPLAN)ZEVIEW, CLEANUP AND ABATEMENT ORDER (CAO)NO. 5-00-707, <br /> FORMER UNOCAL STATION##5098 AT 5606 PACIFIC AVENUE,AND <br /> FORMER MONTGOMERY WARDS AUTO SERVICE AT 5400 PACIFIC AVENUE,STOCKTON, <br /> SAN JOAQUIN COUNTY, <br /> I reviewed the 29 November 2004 Addendum to the Geochemical Evaluation Regarding Potential Chromium <br /> Mobilization During Ozone Treatment (Workplan), submitted by ENSR International (ENSR)on behalf of <br /> Unocal The Workplan proposes a Bench Scale Testing(BST) to evaluate the site-specific geochemistry of <br /> groundwater and soil The Workplan provides the laboratory scope of work and lists the following goals for the <br /> lie <br /> BST ' <br /> • "Determine whether ozonation of site materials can remove chemicals of concern (CDCs)' <br /> • "Determine whether removal is due to destruction and or volatilization" <br /> • "Estimate the ozone demand ofsoil and water" <br /> o "Determine the effect of ozonation on secondary groundwater parameters" <br /> • Assess the potential formation and fate of chromium YI(Cr(VI))" <br /> • Measure changes in total suspended solids (TSS) due to ozonation in order to assess potential of to-situ <br /> treatment to reduce permeability of the aquifer" <br /> IThe Workplan states that the BST will commence 15 days after Regional Board staff approval and last <br /> approximately 45 days <br /> I I concur to the Workplan for the BST The BST Report, due 30 days after completion of the BST, should <br /> include either a Workplan for an In-situ Ozone Injection Pilot Study, or a recommendation for a new remedial <br /> alternative if you determine that In-situ Ozone Injection is not appropriate from the results of the BST <br /> "You may call me at(91 4615 for questions or additional information <br /> f�1 X41 <br /> y <br /> MES L BARTON, R G <br /> Engineering Geologist <br /> cc Mr Mark Owens,UST Cleanup Fund, SWRCB, Sacramento <br /> Mr Mike Infurna, San Joaquin County Environmental Health Division, Stockton <br /> Ms Jill Tracy,Esq ,UNOCAL, Brea <br /> Mr Ben Heningburg,ENSR International, Sacramento <br /> Mr Gary Hall, GHH Engineering,Inc ,Auburn, CA <br /> California Environmental Protection Agency <br /> ��Recycled Paper <br />