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Nestle Foods Corporation 2 29 July 1990 <br /> 8) When municipal well MW-9 becomes operational it will be included in the <br /> quarterly sampling program. <br /> Nestle's schedule includes the submittal of the Phase VI Data Report in mid-January, <br /> 1991, and the submittal of the Feasibility Study Report by 1 May 1991 . <br /> SUMMARY REPORT ON THE VACUUM EXTRACTION SYSTEM <br /> Gary Reents' 30 March 1990 comment letter, referred to earlier, included a request that <br /> Nestle submit a comprehensive report on the operation and performance characteristics <br /> of their on-site soil vapor extraction system, and a workplan for the implementation <br /> of this system as an off-site interim remedial measure at the well M-8 location. <br /> Nestle submitted this report on 16 May 1990. I have reviewed this report and I have <br /> the following comments: <br /> 1) Several times in the report the consultant states that the vacuum extraction <br /> system has proven effective in reducing TCE concentrations in the <br /> unsaturated soils to very low levels. However, no soil sampling data is <br /> provided to substantiate this claim. The basis for this conclusion must be <br /> provided. <br /> In addition, the effectiveness of this remedial action is also dependent <br /> upon the amount of time required to clean up the contaminated soils, and <br /> reduce or eliminate their leaching potential . Hence, how long will it take <br /> to reduce the TCE levels in the unsaturated zone to levels with minimal <br /> leaching potential? Also, have groundwater levels of TCE in the vicinity <br /> of the pilot test site (the decaffination building) decreased since the <br /> operation of the pilot study? <br /> Finally, this system has the potential to strip volatile organic compounds <br /> from both the solid (soil ) and liquid (groundwater) phases. Since the pilot <br /> test is in an area of greatest TCE groundwater contamination and since two <br /> of the vapor extraction wells are screened 20 feet into the water table <br /> aquifer, what's the relative percentage of the extracted TCE from each <br /> phase? <br /> The quantification and documentation of the effectiveness (both the ability <br /> to reduce VOC levels in the soils to 'non- or minimal leachable' levels, and <br /> the time required to achieve this reduction) will be necessary to evaluate <br /> this remedial alternative in the Feasibility Study portion of this <br /> investigation. The above concerns regarding the effectiveness of the vacuum <br /> extraction system are also applicable to the localized chloroform <br /> remediation site. <br /> 2) Nestle's proposed off-site interim remedial measures include a vacuum <br /> extraction system (similar to the on-site system), the extraction of <br /> groundwater from the existing M-8 wells (with treatment by UV Light and <br /> Hydrogen Peroxide Oxidation and effluent disposal to the City of Ripon <br /> sewerage system) , and in-situ bioremediation using the ECOVA bioremediation <br /> system. The vacuum extraction system will utilize the existing water table <br />