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California conal Water Quality ConJW Board <br /> Central Valley Region <br /> v Robert Schneider,Chair <br /> Dan Skopec Arnold <br /> Acting Secretary Sacramento Main Office Ail QY Schwovernegger <br /> 11020 Sun Center Drive N200,Rancho Cordova,California 95670.61 � Governor <br /> Phone 45 <br /> http:%(vvww.wate boards c gov/entraly ley Etj*kq �1 SERV CESS <br /> PERM � <br /> May 15, 2006 <br /> Mr. Mark Adams <br /> Lincoln Center Environmental Remediation trust <br /> 137 Park Place <br /> Point Richmond, CA 94801 <br /> WORK PLAN TO CONDUCT A FOCUSED MEMBRANE INTERFACE PROBE <br /> INVESTIGATION, LINCOLN CENTER, STOCKTON, SAN JOAQUIN COUNTY <br /> Staff of the Central Valley Regional Water Quality Control Board (Regional Board) has <br /> received the Work Plan (WP) to Conduct a Focused Membrane Interface Probe (MIP) <br /> Investigation for the Lincoln Center Site (the Site), Stockton. The letter WP is dated April 27, <br /> 2006, and was received by the Central Valley Regional Board on April 28, 2006. Your <br /> environmental consultant, LFR Inc., of Emeryville prepared the WP on your behalf. <br /> A pilot study is proposed to evaluate enhanced bioremediation of groundwater in the vicinity of <br /> the Bank of Stockton, which is located east of the A Zone Extraction System at the northeast <br /> corner of Pacific Avenue and West Benjamin Holt Drive. The purpose of this WP is to aid in <br /> the design of an effective lactate delivery system by assessing the extent of higher- <br /> concentration chlorinated solvents in this area. Hydrogeologically, this area between the two <br /> extraction systems appears to be stagnant with respect to the flow and capture of groundwater <br /> in the extractions system. Therefore, concentrations of chlorinated solvents are not declining <br /> at a satisfactory rate. <br /> Staff concurs with the proposed MIP objectives and Scope of Work (SOW). However, we <br /> recommend the following issues be discussed in the reporting of the MIP investigation data. <br /> 1. In the Biannual Groundwater Monitoring Report for 2005, PCE was detected at 3,100 <br /> µg/l- in MW-108A (A Zone Well), and cis-l,2-dichloroethene (DCE) was detected at <br /> 1,100 ltg/L in 2058 (B Zone Well). Please discuss the threshold values at which <br /> concentrations of PCE and its breakdown products would be too toxic for microbes to <br /> survive and consume the carbon source being provided. <br /> 2. In the B Zone, it appears that biodegradation is already occurring due to the consistent <br /> presence of PCE breakdown products. However, it also appears that the degradation <br /> pathway may be stalling at DCE and vinyl chloride (VC), which is present in <br /> concentrations of concern in the B Zone near the western boundaries of the Site. <br /> Please discuss how the incomplete destruction of PCE to harmless end products will be <br /> addressed in designing and implementing an enhanced bioremediation pilot study. <br /> California Environmental Protection Agency <br /> Co Recycled Paper <br />