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AECOM <br /> AECOM Environment <br /> 10461 Old Placerville Road, Suite 170 <br /> Sacramento,California 95827 <br /> T 916.362.7100 F 916.362.8100 www.aecom.com HEMMED <br /> November 26, 2008 <br /> DEC 01 2008 <br /> Mr. James L. Barton ENVIRONMENT HEALTH <br /> Central Valley Water Board PERMIT/SERVICES <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, California 95670 <br /> RE: Request for Performance Monitoring Plan Reduction <br /> 5400/5606 Pacific Avenue, Stockton, California <br /> Cleanup and Abatement Order No. 5-00-707 <br /> Former Montgomery Wards/Former Unocal Station#5098(Chevron#306620) <br /> ENSR Project#01231-154-R50 <br /> Dear Mr. Barton: <br /> AECOM Environment(AECOM), formerly ENSR Corporation (ENSR), on behalf of Chevron Environmental <br /> Management Company(EMC), presented to the Central Valley Water Board (CVWB) on June 20, 2008 a <br /> Performance Monitoring Plan (PMP) for the upgraded remediation system for the former Montgomery <br /> Ward, LLC (Wards) service station located at 5400 Pacific Avenue and the former Unocal service station, <br /> located at 5606 Pacific Avenue, Stockton, California, referenced collectively herein as the Site. In a letter <br /> dated July 24, 2008, the CVWB, with reservation that some of the activities proposed in the PMP were <br /> excessive, allowed for the work to proceed as proposed in the PMP. To date, the baseline event and <br /> three monthly events (August, September, and October) have been conducted, as detailed in the PMP. In <br /> preparation for the second half of the PMP events, upon securing an encroachment permit from the City of <br /> Stockton to access half of the selected wells detailed in the PMP, ENSR was notified of the Holiday <br /> Encroachment Work Moratorium from November 22, 2008 to January 4, 2009 imposed by the City of <br /> Stockton. With the moratorium, two sampling events, as currently scheduled, would be eliminated from <br /> the PMP. Additionally, postponing the PMP events until after the moratorium would not be efficient since <br /> costs associated with the PMP activities incurred after January 31, 2009 are not pre-approved, as stated in <br /> a letter dated July 29, 2008 from the State Water Resources Control Board. <br /> After reviewing the data collected from the first three performance monitoring events following start-up of <br /> the remediation system for the Site and the system operational parameters, AECOM puts forward the <br /> position that sufficient data have been collected to evaluate the initial operation of the upgraded air sparge <br /> (AS) and soil vapor extraction (SVE)system. The PMP data, together with the data previously submitted <br /> in the most recent quarterly monitoring report dated October 9, 2008 (Quarterly Groundwater Monitoring <br /> and Remediation Status Report and Updated Site Conceptual Model for the Third Quarter of 2008, <br /> ENSR), have demonstrated that the AS/SVE system will be effective in addressing the elevated fuel <br /> hydrocarbon concentrations at the Site. <br /> EMC and AECOM have engaged the property owner, Stone Brothers and Associated General Partnership <br /> (Stone Bros), by discussing the PMP data, as well as, the information regarding the moratorium with Stone <br /> Bros. In consideration of the moratorium restriction and the evaluation of the PMP data, AECOM is <br /> requesting approval from the CVWB to discontinue the remainder of the PMP events. <br />