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California Regional Water Quality0 Cont <br /> Central Valley Region <br /> Terry Tamminen Robert Schneider,Chair DEC j 2004 <br /> Secretary for ENV Arnold Schwarcenegger <br /> Sacramento Main Office IRONMENT overnor <br /> Environmental Internet Address: http://www.swrcb.ca.gov/rwgcb5 PER <br /> Protection 11020 Sun Center Drive#200 Rancho Cordova,CA 95670-6114 <br /> Phone(916)464-3291 <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 /> WORKPLAN REVIEW, CLEANUP AND ABATEMENT ORDER (CAO)NO. 5-00-707, <br /> FORMER UNOCAL STATION#5098 AT 5606 PACIFICA VENUE,AND - <br /> FORMER MONTGOMERY WARDS AUTO SERVICE AT 5400 PACIFIC AVENUE,STOCKTON, <br /> SANJOAQUIN 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 /> BST: <br /> • "Determine whether ozonation of site materials can remove chemicals of concern (COCs)" <br /> • "Determine whether removal is due to destruction and or volatilization" <br /> • 'Estimate the ozone demand ofsoil and water" <br /> • 'Determine the effect of ozonation on secondary groundwater parameters" <br /> • Assess the potential formation and fate of chromium VI(Cr(VI))" <br /> • Measure changes in total suspended solids('TSS) due to ozonation in order to assess potential of in-situ <br /> treatment to reduce permeability of the aquifer" <br /> The Workplan states that the BST will commence 15 days after Regional Board staff approval and last <br /> approximately 45 days. <br /> 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 /> ou may call me at(91 461-46 15 for questions or additional information. <br /> AMES <br /> L.BARYON,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 /> 0 Recycled Paper <br />