ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study 9.2.3.3 Relative Cost The relative cost of PRB composed of ZVI downgradient of the area of higher TCE concentrations beneath the Site (approximately 700 linear feet) to an average depth of 60 feet bgs would be classified as medium (< $5,000,000). A PRB installation to encompass COC-affected groundwater in the Intermediate Aquifer is not considered implementable and costs for such an installation have not been provided. 9.2.3.4 Conclusion The installation of a PRB composed of ZVI has been retained for further evaluation for the Upper Aquifer beneath the Site. A PRB installation will not be considered further for Intermediate and Lower Aquifers or for off-site areas. 9.3 In-situ Treatment 9.3.1 In-situ Physical Treatment In-situ physical treatment relies on mechanical processes, such as stripping or volatilization, to remove COC mass from a source area. In the case of TCE and daughter products, this would require a vapor collection system such as SVE. Example technologies include air sparging. Air sparging entails the injection or "bubbling" of ambient air into the aquifer to form a zone air channels that strip volatile organics from groundwater. In air sparging applications, treatment is limited by diffusion of volatile contaminants into the air channels""' Dissolved COCs will partition into the vapor phase, eventually escaping from the aquifer for collection. 9.3.1.1 Effectiveness In situ physical treatment technologies can effectively remove CDCs; however, for a physical method to succeed, vapors must escape from the remediated saturated soils to an overlying soil formation that is permeable to airflow to allow for collection. Due to the nature of the Site lithology, injected air could cause vapors to migrate laterally beneath clay layers that are present 40 to 50 feet bgs. Similar constraints are present in other areas of VOC groundwater impacts, including Upper and Intermediate Aquifer zones near the WWTP. 9.3.1.2 Implementability As stated in the previous section, in situ physical treatment is not implementable because clay lenses generally cover or partially cover the Study Area. 9.3.1.3 Relative Cost Since effectiveness and implementability are not acceptable, cost is irrelevant. 9.3.1.4 Conclusion Based on the analysis above, in-situ physical treatment is removed from further consideration as a feasible remedial technology. 31