ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study 11.5 Short-Term Effectiveness Alternatives 3 and 4 achieve remedial action objectives in the shortest time periods, 12 and 15 years respectively. Also, these alternatives are more protective of health and the environment because they address the highest concentration areas upon initial implementation. 11.6 Implementability Alternative 1 requires no implementation. The downsides of pump and treat technologies hamper the implementation of Alternatives 2 and 3. Also, the large area of in-situ chemical treatment required for Alternative 3 makes this alternative difficult to implement. Alternative 4 is the most implementable alternative. Allowing for future in-situ treatment or a subsurface barrier in the highest concentration areas only, shallow source area of the plume makes Alternative 4 realistic and achievable. 11.7 Cost No cost is associated with Alternative 1. Alternatives 2 and 3 are both high cost remedial alternatives. Alternative 4 achieves remedial action objectives within the same time frame as Alternative 3, at lower cost (see Appendix D). 11.8 Recommendations Alternative 4 clearly stands out as the remedial alternative that best meets all evaluation criteria. However, there are certain aspects of the applicability of some of the technologies that are subject to field verification. Therefore, treatability testing for any future in-situ chemical treatment or subsurface barrier technologies is recommended to establish performance criteria, including the following: 1. Sufficiently rapid treatment rates 2. Manageable treatment byproducts (ability to obtain WDR permit) 3. Simplicity and reliability of process 4. Anticipated capital and O&M costs 5. 75% mass reduction at areas targeted for source reduction (relative to the concentrations identified in the 2005 investigation and documented in the April 2006 Initial Testing and Characterization Report from Geomatrix1v) This alternative assumes that groundwater extraction from the Upper Aquifer (within the upper A-zone and lower A-zone) will continue for up to three years at the Site, at which time in-situ treatment, or subsurface barrier technologies, would be considered at the Site if dissolved COC concentrations have not been reduced to the extent that RAOs are met. Additional components of this alternative include institutional controls and monitoring. Institutional controls would take the form of coordination with the City of Ripon, reduced or eliminated pumping at some municipal, private and agricultural wells, and ongoing elimination of known vertical conduits. Monitoring of COC levels to assess the 46