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Nestle USA, Inc.—Ripon, CA January 28, 2011 <br /> 2011 Revised Feasibility Study <br /> If necessary, a post-remediation investigation will be implemented at the Site <br /> following the termination of groundwater extraction, in order to confirm the <br /> effective remediation of source areas. If sampling results from the post- <br /> remediation investigation indicate residual VOC concentrations in groundwater <br /> are sufficiently high to warrant a more aggressive remedial approach, then in-situ <br /> options such as biological or chemical reduction or oxidation and/or impermeable <br /> and permeable barrier technologies (see Section 9) will be considered for the <br /> Site. <br /> Several municipal and private wells (MW-3, MW-11, MW-7, MW-9, and irrigation <br /> wells at Ripon Christian and Ripon Public schools) would no longer be active as <br /> part of the institutional controls proposed under Alternative 4. All aquifers are <br /> monitored for evidence of ongoing intrinsic remediation, under the guidelines of <br /> an intrinsic remediation monitoring plan currently under development. Figure 10 <br /> provides an overview of the main remedial components of Alternative 4. <br /> 10.1.4.2 Assessment <br /> Alternative 4 protects human health and the environment by decreasing COC <br /> concentrations to below 5 pg/L in soil and groundwater in approximately 12 to 15 <br /> years and by containing the plume. This alternative minimizes COC impacts to <br /> municipal and private wells. Likewise, the ARARs are achieved within 15 years <br /> for the Study Area. <br /> Long-term effectiveness and permanence of this alternative is high. Residual <br /> risk is low, since groundwater COC concentrations are reduced to below 5pg/L. <br /> Since pump-and-treat technology is implemented for a limited period of time, the <br /> long-term problems associated with this technology are eliminated. Toxicity, <br /> mobility and volume of COCs are reduced. The highest concentration source <br /> areas are removed. Plume migration is reduced by eliminating the conduits <br /> between aquifers and by decreasing pumping from wells that pull the plume <br /> away from the source area. Finally, monitored intrinsic remediation supports the <br /> continued degradation of the plume by natural dispersion and biodegradation. <br /> If deemed necessary, following the post-remediation assessment of groundwater <br /> concentrations in the Upper Aquifer beneath the Site, an in-situ chemical <br /> treatment or barrier technology would be implemented. Minor impacts to the <br /> subsurface environment are possible with some types of chemical treatment or <br /> subsurface barrier options. However, a waste discharge permit would be required <br /> for in-situ chemical treatment. The regulatory requirements contained in a waste <br /> discharge permit protect the environment. <br /> Targeting the highest source area for any future in-situ chemical treatment <br /> removal is much more practicable than attempting treatment over much larger <br /> and deeper areas suggested in Alternative 3. Furthermore, targeting the highest <br /> concentration source is sufficient to create desirable remedial results. <br /> Institutional controls required in this alternative are relatively easy to implement. <br /> Overall, this alternative is the most implementable for the resulting effect. <br /> 44 <br />