ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study groundwater), while others can both limit migration and reduce COC concentrations. Therefore, containment actions can meet the RAOs of containing/capturing the COCs from the Study Area and reduce COC extent by limiting additional COC mass from leaving the contained area, which also protects human receptors, or by reducing COC concentrations within the Study Area. For example, an impermeable barrier acts to hold the high COC concentrations within that area, whereas pump-and-treat technology can create a cone of depression to contain the high COC concentration area and slowly reduce concentrations in that area by removing and treating the extracted water. 8.3 In-situ Treatment In-situ treatment is a mass-removal/mass-reduction approach whereby COCs are destroyed in place or physically removed or immobilized. Some technologies physically strip the CDCs from the aquifer, others introduce chemical reagents to destroy COCs in place or use biological activity enhancement to transform COCs to environmentally benign end-products. Passive in-situ treatment, or intrinsic remediation, involves COC destruction by natural mechanisms, such as biodegradation. Active forms of in-situ treatment include stripping (air sparging), enhanced bioremediation, or chemical treatment by oxidizing or reducing agents. Often, active in-situ treatment will take the form of a permeable reactive barrier, with a line of injection points intercepting the leading edge of the plume. Active in-situ treatments can control migration of CDCs and reduce COC extent by significantly reducing concentrations within the target treatment area. Application of in-situ treatments can also generate by- products (e.g., VC) and mobilize natural occurring chemicals in groundwater (e.g., dissolved arsenic) which must be considered and tested for when considering these technologies. 8.4 Institutional Controls Institutional controls do not control COCs themselves but can help meet RAOs by limiting exposure and horizontal or vertical migration of COCs. Examples may include the following: • Restricting installation of wells within, or in the vicinity of, the Study Area • Groundwater management to prevent COC migration, and, • Proper decommissioning to seal conduit wells (i.e. wells that could potentially serve as preferential migration pathways, especially those wells that are screened in multiple aquifers). • Property use restrictions to limit non-desired activities, such as installation of groundwater wells that could promote unwanted COC migration. This control is considered as interim Remedial action measure until RAOs are achieved and no further control is required. 23