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1 .4:N California Regional Water Quality Control BoardL. - 1 <br /> Qm; Central Valley Re ion <br /> Robert Schneider. Chair <br /> lerry Ta<l limn Arnold Sebwarzensgger <br /> ry for 5acrunato Main Office Governor <br /> 1= nrMental Interne;Address hmpllwwwswrr-b ea goy/rwgeb5 <br /> protection l 1020 Sun Censer Dnve ROO Rancho Cordova.CA 9567M 114 RECEIVED <br /> Mom(936)46a-391 <br /> 5 November 2004 NOV 0 5 209 <br /> Mr John Fray Mx Jay Allen <br /> Union Oil Company ofCalifomia Stone Brothers Management Company <br /> I 276 Tank Farm Road 1024 W Robmhood Dr <br /> P O Box 1069 Stockton, CA 95207 <br /> San Luis Obispo CA 93406 <br /> WORKPLAN APPROVAL AND REPORT REVIEWS, CLEANUP AND ABATEMENT ORDER (CAU) <br /> IVO. 5-00-707, FORMER UNOCAL STA TION#5098 AT 5606 PA CIFIC A VENUE,AND <br /> FORMER.MONTGOMERY WARDS AUTO SER P7CE AT 3400 PACIFIC A VENUE STOCKTON, <br /> SAN JOAQUEV COUNTY, <br /> I reviewed the 3 November 2004 Work Plait to Evaluate Potential SVEIAS System Enhancements and Additional <br /> Well Installation within the Deeper Aquifer Units (Workplan) and 29 October 2004 Updated Site Conceptual <br /> Model, Quarterly Monitoring and Remediatron Status, Well Installation, and Well Destnictwn Deport, Third <br /> Duarter 2404(3Q2004 Report),subt=irtted by ENSR International (ENSR) on behalf of Unocal I also reviewed <br /> the 8 October 2004 MW-1 Redevelopment Report (MW-1 Report), submitted by GIH Engineering Inc (GHH) on <br /> lie behalf of Stone Brothers Management Company. <br /> The Workplan proposes a time schedule that correlates to the dates listed in my 4 October 2004 Letter Request to <br /> evaluate additional enhancements to the existing treatment systems, and the installation of momtonng wells <br /> fMW-31 and MW-32, in order to better define the plume ltmtts and flow direction of groundwater in the C-zone <br /> acid D-zone within the footprint of the Former Montgomery Wards Auto Service (Wards) The Workplarn states <br /> that the Air 5parging(AS)well AS-26 airflow rate was adjusted downward to prevent further movement of the <br /> B-zone groundwater plume to the north and east of Former Unocal Station#5098 (Unocal) <br /> The 3Q3004 Report provides groundwater results from monitoring well samples collected from <br /> 14 to 22 3uly 2004 Total Petroleum Hydrocarbons (TPH)as gasolene and benzene groundwater concentrations <br /> increased in the treatment area at Wards(MW-1 through MW-9) and to the north and east of Unocal (MW-14 <br /> and MW-18D) Asa result of my 18 June 2004 Notice of Violation, three new monitoring wells(NM-28 through <br /> h W-30) were installed to redefine the luruts of the groundwater plume at Wards On 24 September 2004, the <br /> Soil Vapor Extraction(SVE) System was restarted and the AS System reverted from pulsed operation back to <br /> continuous operation ENSR conducted monthly groundwater sampling and analysis on selected monitoring <br /> wells in August and September of 2004,to facilitate better understanding of the hydrodyn=ucs of the restarted <br /> 5-VE/,AS systems Due to pending new consuuctlon, NI—Ar-9R was installed Mud 'LV T-7 was ubiuidvu'cu VIL LV <br /> August 2004 An attempt to rehabilitate MW-1,which was contaminated by intrusion of a parking lot oil-based <br /> Isealant, occurred on 22 September 2004 <br /> The MW-1 Report stated that redevelopment activities (scrubbing and groundwater purging) fbAcd to remove all <br /> traces of the oil-based sealant. MW-1 confirmation analyses reported TPH as motor 0s1 (TPHmo) in the primary <br /> (1,900 �LgIL) rind split(5,500 µglL)groundwatcr satrapies TPHmo was not present in MVV-1 pnor to the <br /> incident, <br /> I California Environmental Protectcvn Agency <br /> Q�ltec7'C1�d P.apCr <br />