ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study cis-1,2-DCE and VC were 97.1, 240, and 47 pg/L, respectively); well M-31 C1 is located approximately 750 feet east of the southeast WWTP and approximately 4,000 feet south (upgradient) of the Site. Relatively high VC concentrations were reported in groundwater samples taken from wells M-17C1 and M-20C1. These two wells are located north of the WWTP and south of the Site. For example, VC concentrations are one to two orders of magnitude above cis-1,2-DCE and TCE concentrations in groundwater taken from these two wells. The presence of TCE breakdown products, the spatial distribution of TCE breakdown products in groundwater, and the historical groundwater flow patterns, suggest that the likely origin of the dilute COC plume that underlies the largest portion of the Study Area is the historical discharge of untreated industrial wastewater at or near the WWTP. Recent reductive dechlorination trends indicate that Intermediate Aquifer CDCs are undergoing intrinsic remediation. 6.2.3 Lower Aquifer (210+ feet bgs) The highest concentrations of COCs detected in Lower Aquifer wells were reported at NPC well TH-10. This well was constructed with well screens in both the Intermediate Aquifer and the Lower Aquifer, at depths between 120 and 210 feet bgs. The well was modified in April 2009 by filling the lower portion of the well with cement slurry in order seal the well from the Lower Aquifer. The TCE, cis-1,2-DCE, and VC concentrations reported for the April 2008 sample were 61, 170, and 250 pg/L, respectively. Downward flow was documented in this well at a rate of 0.4 gpm""". Therefore, samples from this well represent a starting concentration for Lower Aquifer COC impacts. COCs from the Intermediate Aquifer bypassed the Corcoran Clay and migrated to the Lower Aquifer through conduit wells such as TH-10. Well TH-10 is the first documented COC source within the Lower Aquifer. Other COC sources to the Lower Aquifer have been identified, such as the former idle municipal wells MW-4 and MW-6. Downward ambient (i.e. non-pumping) groundwater flow in these wells was documented to range from 23 to 68 gallons per minute" ' It is possible that other conduit wells may exist near the WWTP, and at other locations throughout the Study Area. These isolated COC sources could give rise to relatively narrow, localized COC plumes, where the distribution of CDCs likely reflects the complex history of temporally variable vertical gradients, conduit wells, and pumping. A similar mechanism for COC impacts involving wells MW-4, MW-6. and the former Nestle production wells most likely explains the variable concentration trends seen in sample results from wells M-6D and M-10A, although a specific conduit has yet to be identified. 7 Regulations, Plans and Policies This section provides an overview of regulatory policy applicable to this Site based on existing documentation from the regulatory agencies. The federal and state environmental clean-up requirements consist of three types: chemical-, location-, and action-specific""'. The chemical specific requirements are health-, 17