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LFR Inc. <br /> 2.2.2 Previous Feasibility Studies for Groundwater Remediation using ERD <br /> ERD was retained for secondary screening in the Draft FS. However, ERD was not <br /> retained for remedial alternative development because of concerns about its <br /> effectiveness; <br /> "Results of field studies have shown that this process option can be effective <br /> in enhancing biodegradation of CAHs[chlorinated aliphatic hydrocarbon]. <br /> The technology is most likely to be effective in areas where appreciable <br /> biodegradation is already occurring. As discussed in Section 1, <br /> biodegradation does not appear to be occurring at Lincoln Center or <br /> downgradient from Lincoln Center to a significant degree. Since significantly <br /> altering existing redox conditions in an aquifer is likely problematic, the <br /> effectiveness of this technology at Lincoln Center may be low. Because HRC <br /> is an emerging technology, limited peer-reviewed results are available. <br /> Treatability and pilot studies would be necessary to evaluate the effectiveness <br /> at Lincoln Center" (LFR 2002). <br /> Research and project experience gained since the 2002 Draft FS have shown that PCE <br /> and its daughter products can be effectively remediated using ERD technology. On the <br /> basis of the review of historical and recent groundwater quality data and the local <br /> hydrogeology, LFR proposes to implement ERD in the A zone hydraulically <br /> downgradient from Lincoln Center, namely in the vicinity of the Bank of Stockton. <br /> LFR believes that ERD is an appropriate remedy for this Site for the following reasons: <br /> • The Hazardous Substances are anaerobically biodegradable. <br /> • Conditions at the Site are naturally slightly reducing (e.g., negative oxidation- <br /> reduction potential [ORP] values and generally depressed dissolved oxygen [DO] <br /> levels are present, see Section 3.2) and even stronger reducing conditions can be <br /> generated. <br /> • Natural reductive dechlorination has been observed in A-zone groundwater samples <br /> (e.g., PCE daughter products including ethene and ethane have been observed, see <br /> Section 3.3); therefore, a microbial community capable of driving the reductive <br /> process to completion is present. <br /> • A food-grade substrate can be successfully distributed in the subsurface. <br /> 3.0 ACTIVITIES CONDUCTED IN SUPPORT OF PHASE V IRA <br /> This section includes a summary of activities, and their findings, conducted in support <br /> of the Phase V IRA. These activities included: <br /> wp-PhV_IRA-SeP07-Fim1-06750.dm:ltr Page 7 <br />