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Nestle USA, Inc.—Ripon, CA January 28, 2011 <br /> 2011 Revised Feasibility Study <br /> the least effective alternative presented in this evaluation. Reduction of toxicity <br /> and volume come only from natural dispersion and biodegradation processes <br /> occurring in the subsurface. Implementability and cost are negligible as there is <br /> nothing to implement. <br /> 10.1.2 Alternative 2 <br /> This alternative assumes that current technologies in use within the Study Area <br /> continue with modification. <br /> 10.1.2.1 Description <br /> In the Alternative 2 scenario, the existing groundwater pump-and-treat systems <br /> are expanded to control migration in source areas in all three primary aquifers. <br /> New extraction and treatment wells are installed and operated within the <br /> Intermediate and Lower Aquifers at the Stockton Avenue location, the Site, and <br /> downgradient of the NPC and WWTP lagoons. This alternative results in <br /> theoretical average pumping of approximately 1.5 MGD. Identified vertical <br /> conduits are eliminated. In addition, several municipal and private wells (MW-3, <br /> MW-11, MW-7, MW-9, and irrigation wells at Ripon Christian and Ripon Public <br /> schools) would no longer be active as part of the institutional controls proposed <br /> under Alternative 2. All aquifers are monitored for evidence of ongoing intrinsic <br /> remediation. SVE is implemented for vadose zone remediation, which is <br /> completed. Figure 8 provides an overview of the main remedial components of <br /> Alternative 2. <br /> 10.1.2.2 Assessment <br /> Overall protection of human health and the environment is provided by limiting <br /> vertical and horizontal migration of COCs (containing the plume). This alternative <br /> minimizes COC impacts in municipal and private wells. Remedial Action <br /> Objectives are met in approximately 30 years. Long-term effectiveness is heavily <br /> weighted upon the efficiency of extraction wells and treatment systems. If well <br /> efficiencies decrease over time, as has occurred in E-6, the length of time to <br /> achieve ARARs will be extended. Residual concentrations in groundwater are <br /> below RAOs. Long-term O&M and monitoring of treatment systems is extensive. <br /> O&M for extraction wells is anticipated to be considerable and may include <br /> replacing wells when the well efficiency diminished and the pumping rate is not <br /> achievable. <br /> One uncertainty of primary concern is that of treated water disposal. Volume and <br /> TDS concentrations pose the biggest concerns for water disposal. There are no <br /> known methods to manage the significant volume of groundwater (approximately <br /> 530 million gallons per year) which would be generated under this scenario" <br /> This alternative reduces toxicity by removing and treating groundwater. This <br /> alternative will reduce COC concentrations in groundwater below RAOs, but only <br /> addresses saturated soils indirectly (i.e. as groundwater concentrations are <br /> 41 <br />