ARCHIVED REPORTS_2013 ANNUAL REPORT

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Nestl6 USA, Inc., Ripon, California March 26, 2014 2013 Annual Report 2. Stanislaus River stage was at normal low flow during most of 2013, likely related to extreme drought conditions in the region. Because the river exerts a major control on groundwater levels in the Upper and Intermediate aquifers, the average regional horizontal groundwater gradients for each of these aquifers were relatively low in 2013. 3. Groundwater mounding was observed beneath the City of Ripon WWTP lagoons/recharge pond and Diamond Pet Foods percolation fields in the Upper and Intermediate aquifers resulting in an elongated radial flow pattern. During most of 2013, the top of the groundwater mound was located beneath the City's recharge pond or nearby. 4. Municipal wells MW-3, MW-5, and MW-10 were the most active pumping wells in the Study Area during 2013. When operating, the wells produced localized groundwater level depressions with increased flow towards the wells. 5. The spatial distribution of TCE in the Upper Aquifer has not increased over the past three years. Wells M-57A and M-58A have defined the northwestern boundary of the plume in the Upper Aquifer. 6. The distribution of cis-1,2-DCE and VC concentrations in the Intermediate Aquifer has not increased over the last five years, and may be an indication of plume stability. Higher concentrations of cis-1,2-DCE compared to TCE concentrations, and the presence of VC observed in Intermediate Aquifer monitoring wells, is indicative of intrinsic remediation processes as documented in Attachment 4 of the 2011 Revised FS. 5.2 GROUNDWATER EXTRACTION AND TREATMENT 1. Data from the IRAP system show a continued reduction of COC concentrations in 2013. This is indicative of an overall reduction of COC mass in the area of influence generated though the pumping of wells EU-3, EU-4, and EI-1. 2. Groundwater drawdown and elevation profiles in the area of the IRAP system continue to indicate that the capture zone induced through pumping is consistent with the intended area of capture as originally predicted through groundwater modeling. 5.3 MIGRATION CONTROL 1. Groundwater extraction wells (EU-3, EU-4, and EI-1) are containing the migration of CDCs, as evidenced by drawdown observed near these wells (Figure 3-1 through Figure 3-4). 2. The MW-3 depth profiling results indicated the source of most of the COCs in this location was the Intermediate Aquifer from depths between 127 feet bgs and 140 feet bgs. 6 PLANNED ACTIVITIES AND RECOMMENDATIONS FOR 2014 The following reporting and field activities are proposed for 2014 based on the conclusions presented in Section Error! Reference source not found.. 21