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0 i UENVIRONMENTAL MANAGEMENT&CONSULTING ENGINEERING September 27, 2007 001-06750-07 Mark A. Adams, P.G. Point Environmental 137 Park Place Richmond, California 94801 Subject: Phase V Interim Remedial Action Detailed Plan, Lincoln Center, Stockton, California Dear Mr. Adams: Enclosed is the "Phase V Interim Remedial Action Detailed Plan, Lincoln Center, Stockton, California" ("the Phase V IRA Detailed Plan"). The Phase V IRA Detailed Plan was prepared to address relatively elevated levels of tetrachloroethylene (PCE) and its daughter products in the A- and B-groundwater aquifers in the vicinity of the Bank of Stockton, an area that is hydraulically downgradient from Lincoln Center in Stockton, California. This Phase V IRA Detailed Plan is presented in accordance with the "Amended First Final Consent Decree Order, Judgment and Reference to Special Master," filed with the Court on June 4, 1999. In late 2006, LFR Inc. (LFR) conducted a groundwater investigation in the vicinity of the Bank of Stockton to assess the vertical and lateral extent of the relatively higher concentrations of Hazardous Substances in this area. Results of this investigation were presented in LFR's "Results of Focused Membrane Interface Probe Investigation in the Vicinity of the Bank of Stockton, Lincoln Center, Stockton, California," dated March 29, 2007. The report recommended designing and implementing enhanced reductive dechlorination (ERD) for the Bank of Stockton area, using ERD injection remediation technology in A-zone groundwater. Active remediation of the B zone was not recommended by LFR in the aforementioned report because Hazardous Substances appear to be undergoing complete anaerobic dechlorination under natural conditions, which is effectively remediating this zone. The preparation of a work plan to implement ERD in the form of an interim remedial action (IRA) detailed plan was approved by the Regional Water Quality Control Board (RWQCB) in a letter from Ms. Marie T. McCrink dated May 11, 2007, with the following recommendations: (1) conduct further evaluations of chemical and biological processes that allow for successful ERD to occur; (2) conduct ERD of the B-zone aquifer as clear evidence that the dechlorination reaction is proceeding completely to harmless end products at the time of the May 11, 2007 letter; (3)prepare a work plan in the form of an IRA detailed plan with the following components: (a) evaluation phase, (b) cost benefit analysis of potential carbon sources, (c) evaluation of terminal electron 510.652.4500 m 510,652.2246 f 1900 Powell Street, 12th Floor www.ifr.com Emeryville, California 94608-1814 Offices Nationwide