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California Regional Water Quality Control-Board Central Valley Region� Robert Scbneicier.Cbsir erry Tamminen � Arnold Schwarzenegger Secretary for Sacramento Main Office Governor Environmental Internet Address ht0.lwww swrcb ca pvlrwgcb5 RECEIVE[ ' Protection 11020 Sun Center rhnve#200 Rancho Cordova,CA 95670-6114 Phone(916)464-3291 OCT 0 5 2004 ' 4 October 2004 Mr Bob Hopkins Mr Jay Allen Union Oil Company of California Stone Brothers Management Company 276 Tank Farm Road 1024 W Robinhood Dr P O Box 1069 Stockton,CA 95207 San Luis Obispo, CA 93406 LETTER REQUEST, CLEANUP AND ABATEMENT ORDER (CAO)NO. 5-00-707;FOR2i ER UNOCAL ' STATION#5098 AT 5606 PACIFIC AVENUE,AND FORMER MONTGOMERY WARDS AUTO SERVICE AT 5400 PACIFIC AVENUE,STOCKTON,SAN JOAQUIN COUNTY, Regional Board staff reviewed the 15 September 2004 Request for Extension to Restart SVE System and Evaluation of Potential Enhancement to SVE System(Letter), submitted by Unocal The Letter proposes a date of 15 January 2005 for submitting a report recommending a proposal for enhancement to the existing SVEIAS system,to help cease plume movement Background My letter dated 15 May 2004 requested a Workplan by 15 June 2004,to comply with CAO No 5-00-707,Order No 15,which states "If groundwater monitoring indicates that the groundwater plume has migrated beyond laterally or vertically defined limits during the quarter, the quarterly report shall include a workplan and schedule, with work to begin within 30 days of a report submittal, to define the new plume limits and cease plume movement The Workplan,received 15 June 2004,did not include a schedule to beam woik to redefining the limits of the groundwater plume within 30 days A Notice of Violation(NOV) for CAO No 5-00-707 was issued on 18 June 2004 The NOV required implementation of the approved Workplan by 15 July 2004, and also required submittal of a Report by 1 August 2004,showing the steps taken to cease plume movement You did comply with both NOV deadlines by installing the monitoring wells and providing the Report,which redefined the limits of the groundwater plume and began the process for restarting the SVE/Air Sparging system On 14 June 2004,the Air Sparging(AS)system was overhauled and restarted The SVE system required a new air permit, and was scheduled to start by 15 September 2004 The Soil Vapor Extraction (SVE) system was restarted on 28 September 2004,per email notification received from your consultant ENSR International Inc (ENSR) Additionally,in a phone discussion on 3 September 2004, ENSR proposed enhancing the SVFJAS remediation by Iii-Situ Chemical Oxidation, specifically Ozone Injection Since additional time would be required to evaluate an injection of an In-Situ Chemical Oxidation substance,I suggested that ENSR begin the process by providing a baseline analysis using site soil and groundwater,prior to submitting a Workplan for a bench scale testing for ozone injection A pilot study for ozone injection into the aquifer would also be necessary ENSR provided email copies of the preliminary baseline analyses on 28 September 2004 I concur to the proposed 15 January2005 deadline to provide a Report of the assessment of SVE/AS enhancement,pm-ided the following due elates are met o By 15 October 2004, submit a Workplan outlining the entire process for enhancement to the existing SVE/AS system,to help cease plume movement Also,I have reviewed existing data and request inclusion of additional-monitoring wells needed to enhance-the vertical and lateral extent of contaminants Specifically, adequate characterization is needdd t6-show groundwater flow direction and California Environmental Protection Agency g�Recycled Paper