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Port of Stockton - 4 - 6 September 2013 <br /> Rough and Ready Island <br /> Stockton, San Joaquin County <br /> Required Action: Provide an explanation for this concern within the context of the <br /> requested SCM. <br /> 2. In Section 6.2.2, ERS has indicated that sites which adopt Monitored Natural Attenuation <br /> (MNA) as a remedial approach are reviewed based on the ability to meet seven criteria set <br /> forth in a Monitored Natural Attenuation Assessment Plan (MNAAP). ERS has indicated <br /> that Site 49 has met this criteria based on the historic groundwater monitoring data, and <br /> that MNA is a success at Site 49. <br /> Central Valley Water Board staff do not concur with this assessment based on the <br /> comments presented in this letter. ERS has never submitted a MNAAP for Central Valley <br /> Water Board or DTSC staff review, which will be necessary should ERS propose MNA as a <br /> remedial alternative. <br /> 3. Table 16 of the Revised RI/FS presents a comparative cost analysis for MNA, Enhanced <br /> MNA and In-Situ Chemical Oxidation. Although MNA and Enhanced MNA provide a <br /> breakdown of costs, In-Situ Chemical Oxidation (ISCO) does not. ERS' contention that <br /> ISCO may not be appropriate for the site may be warranted, but this cannot be assessed <br /> without current geochemical groundwater data. ERS proposes a general cost for ISCO of <br /> $500,000 without any detail. Based on previous ISCO projects Central Valley Water Board <br /> with which staff have experience, this estimate is high. <br /> 4. ERS has provided the rationale that the reductive dechlorination occurring at Site 49 is <br /> sufficient to provide a reasonable timeframe to meet water quality objectives (presented by <br /> ERS as MCLs). ERS has presented a timeframe of 14 years on page 21 and 45 years on <br /> page 41. Please provide an explanation of this discrepancy, and/or a rationale for one or <br /> both timeframes. <br /> In summary, Central Valley Water Board staff finds the evidence for MNA insufficient to be <br /> proposed as a stand-alone remedial action for Site 49. ERS needs to evaluate the additional costs <br /> associated with presenting a viable SCM proposing MNA alone, or re-evaluate other remedial <br /> options (ISCO, enhanced bioremediation) for use at Site 49. Other alternatives will still require <br /> ERS to have a thorough understanding of the hydrogeology and geochemistry of the plume at Site <br /> 49. <br /> If you have any questions, please contact me at (916) 464-4607 or kamaru@waterboards.ca.gov. <br /> KATHLEEN AMARU, P.G., C.E.G. <br /> Engineering Geologist <br /> cc: Jose Salcedo, DTSC <br /> Harland Knoll, San Joaquin County Department of Environmental Health <br /> Mark O'Brian, ERS <br />