ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study 9.4.1.2 Implementability A Water Replacement Contingency Plan (WRCP) was implemented in 2007. Since then, several locations have been evaluated for replacement water pursuant to the WRCP. The WRCP outlines the response actions to be taken in a timely fashion, such that the receptors are protected. The appropriate response action depends on well use and the level of COC concentrations detected. The possible response actions include providing bottled water, wellhead treatment, connecting to a municipal source, and the installation of new wells. The willingness of private parties to accept replacement of their water supply, and to accept water replacement options, requires coordination and negotiation with private parties and their representatives. 9.4.1.3 Relative Cost Given the importance and effectiveness of water supply replacement, cost is acceptable for this technology. Cost varies widely between the different methods of water supply replacement. If more than one method of water supply replacement ensures human health and safety, then all the methods must be evaluated to choose the appropriate method agreeable to all parties. 9.4.2 Well Destruction Well decommissioning is most preferred response to an impacted water supply wells already within a groundwater plume. As discussed previously, the well screens on many water supply wells pass through multiple aquifers, acting as a conduit for water from a higher aquifer to flow to a lower aquifer. Vertical gradients near these wells contribute to groundwater flows of approximately 80 gpm from the Upper and Intermediate Aquifers to the Lower Aquifer. Decommissioning these vertical conduits can mitigate the extent of plumes in the Lower Aquifer. Identified vertical conduits related to wells screened across multiple aquifers have already been addressed at several locations through well destructions at the locations indicated in Figure 6. 9.4.2.1 Effectiveness Proper well decommissioning is effective in eliminating conduits that can allow for vertical plume migration. In most instances it should be considered a top priority to reduce and contain the plume. Assuming a vertical conduit is the only exposure pathway from a source area to the Lower Aquifer, then well decommissioning is an extremely effective way to isolate the Lower Aquifer from any overlying impacted groundwater. 9.4.2.2 Implementability Nestle has decommissioned many wells in the study area to minimize plume size. Convincing the well owners to properly decommission the wells is the most difficult step. Although it is not possible to ensure all existing vertical conduits have been identified, exhaustive efforts have been undertaken to detect them. It 38