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• <br /> Nestle Foods Corporation 3 29 July 1990 <br /> well M-8B. Groundwater will be extracted from the existing M-8 wells with <br /> treatment to at least MCL levels. It is not clear if the water table well <br /> M-8 will be employed in both of these systems. <br /> I have the following concerns regarding these remedial measures: <br /> a) An implementation schedule should be submitted. <br /> b) Though I concur with the implementation of the soil gas extraction system <br /> in this area, my concerns expressed above regarding the effectiveness of <br /> this system in reducing soil contaminant levels are still germane, and <br /> need to be addressed. Also, the performance monitoring plans for this <br /> system must be submitted. <br /> c) Will M-8B be utilized in both the gas extraction and ground water <br /> extraction remedial measures? If these remedial measures are run <br /> concurrently, and M-8B is utilized in both remedial actions, than how <br /> will this be done? Also, is M-8B screened throughout the unsaturated <br /> zone? <br /> d) Nestle submitted a proposal on 23 February 1990 regarding a second pilot <br /> test of the ECOVA insitu bioremediation process that apparently addressed <br /> the concerns Gary Reents had with the initial study (Gary Reents' 28 <br /> November 1989 memorandum) . The status of this second pilot test and its <br /> relationship to this off-site proposal to employ the ECOVA system must be <br /> explained. The ECOVA system should not be employed off-site until the <br /> effectiveness of the system is proven on-site. <br /> e) Performance monitoring plans for both the extraction and bioremediation <br /> systems must be submitted? <br /> RISK ASSESSMENT <br /> A copy of the final Draft Risk Assessment Document was submitted on 6 July 1990. This <br /> risk assessment discusses the degree of potential hazards to public health associated <br /> with the Nestle groundwater contamination. Though other potential pathways of exposure <br /> are discussed, the primary focus is the exposure to groundwater. <br /> This assessment determined that the only significant exposure pathway was the <br /> consumptive use of contaminated groundwater, but that the current and future risks <br /> associated with groundwater contamination from Nestle are negligible. This conclusion <br /> was based upon (1) the institutional controls currently in effect, within the City of <br /> Ripon, to restrict the use of contaminated groundwater (apparently the City of Ripon's <br /> municipal code currently prohibits new domestic drinking water wells within the City <br /> limits), (2) the current practice of abandoning private domestic wells and city <br /> municipal wells if they exceed drinking water standards, and (3) that groundwater <br /> remediation activities and the "static" nature of the groundwater plume indicate a <br /> reduced potential for exposure in the future. <br /> Two existing municipal wells, MW4 and MW6, have had low levels (below MCLS) of VOC's <br /> detected, and the public health risks associated with the domestic use of the water <br /> obtained from MW6 (containing VOCs attributable to Nestle) were quantified in this <br />