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EFLV. <br /> ENSR International <br /> 10411 Old Placerville Road <br /> 0), November 2, 2004 Suite 210 <br /> Sacramento,CA 95827-2508 <br /> (916)362-7100 <br /> FAX (916)362-B100 <br /> www ensrcom <br /> Mr James Barton <br />' California Regional Water Quality Control Board <br /> MCEWEID <br /> Central Valley Region <br /> 11020 Sun Center Drive, Suite 200 NOV 0 3 2004 <br /> Rancho Cordova, CA 95670 <br /> EIvVIROIdMEiVT HEALTH <br /> PERMIT/SERVICES <br /> RE Work Plan to Evaluate Potential SVE/AS System Enhancements and Additional <br /> Well Installation within the Deeper Aquifer Units <br /> Former Unocal Station No. 5098 <br />' 5400 and 5606 Pacific Avenue, Stockton, California <br /> Dear Mr Barton <br /> On behalf of Union Oil Company (Unocal) of California, ENSR Corporation (ENSR) has <br /> prepared this work plan for the Former Unocal Station No 5098 at 5606 Pacific Avenue, and <br /> Former Montgomery Wards (Wards) Auto Service located at 5400 Pacific Avenue, Stockton <br /> California The location of the site is shown in Figure 1 and site features are illustrated on <br /> Figure 2 <br /> 10 Wards and Unocal are named jointly responsible for actions necessary to abate the effects of <br /> contamination in the vicinity of the sites In August 2000 Wards and Unocal executed an <br /> agreement for Coordinated Corrective Action for Underground Storage Tank (UST) Fund Claim <br /> No 1760 and UST Fund Claim No 6864 On November 2, 2001, Unocal was named as the <br /> Appointed Representative for the PACIFIC/ROBINHOOD COMMINGLED PLUME In this work <br /> plan, reference to the "site" includes the former Wards and Unocal sites The California Regional <br /> Water Quality Control Board, Central Valley Region (RWQCB) requested this work plan In a <br /> letter dated, October 4, 2004 A copy of the RWQCB letter is included in Attachment A <br /> PMposed Outline and Schedule to Evaluate System Enhancement Options <br /> The following seven activities are currently being conducted or planned to evaluate potential <br /> enhancements to the existing AS/SVE system, to help control plume movement, and to achieve <br /> regulatory closure <br /> 1 Conduct a Remedial System Evaluation (RSE) to objectively review program goals <br /> (containment, receptor protection, and cleanup) in accordance with the Cleanup and <br /> Abatement Order (CAO) 5-00-707, and critically evaluate primary cost categories (labor, <br /> regulatory compliance/reporting, vendors/suppliers, and equipment/maintenance) The <br /> RSE will evaluate the placement of existing air sparge wells, vapor extraction wells and <br /> monitoring wells relative to the changing plume boundaries both vertically and horizontally <br /> _ The results of the_RSE will be used to either re-affirm the goals of the remedial system or to <br /> develop new goals for the existing system and propose enhancements and/or additional- - ---- <br /> 11DcsacramentolprotectslProleds10694015098-2931FinaARepods\Work Plans15098 Work Plan-SVE AS System doc <br /> �a'ArJYr7r'7u " V_r`i ,Sejui,,9 <br />