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Nestle USA, Inc., Ripon, California March 31, 2011 <br /> 2010 Annual Report <br /> 5.1 GROUNDWATER INVESTIGATION <br /> 1. A decline in A-zone groundwater extraction at the Site (from wells EI-1 and EW-1) and <br /> the changes in the pumping schedule at well MW-4 may have caused the increase of <br /> COC concentrations in M-10A. <br /> 5.2 GROUNDWATER MONITORING <br /> 2. Drawdown surrounding the City of Ripon municipal wells and Nestle groundwater <br /> extraction wells in all four quarters of 2010 is evidence of the influence of groundwater <br /> pumping in the Upper, Intermediate, and Lower aquifers. <br /> 3. The groundwater flow directions in each quarter of 2010 in the Upper, Intermediate, and <br /> Lower aquifers are consistent with the flow directions in each corresponding quarter of <br /> 2009. <br /> 4. Groundwater elevation changes in the Study Area during 2010 were primarily seasonal <br /> and were consistent with historical patterns. <br /> 5. Although water levels in the Lower Aquifer increased in 2010, the overall trend continues <br /> to decline since 1998, indicating higher withdrawal from this zone. This is due to <br /> pumping from the Lower Aquifer by the City of Ripon. <br /> 6. Average groundwater elevation changes in the Lower Aquifer between each quarter of <br /> 2010 differ from those in the Upper and Intermediate aquifers. The difference suggests <br /> that the recharge mechanism for the Lower Aquifer is different than for the Upper and <br /> Intermediate aquifers. <br /> 5.3 GROUNDWATER EXTRACTION AND TREATMENT <br /> 7. Data from the Industrial Avenue extraction and treatment system show a continued <br /> reduction of COC concentrations in 2010. This indicates an overall reduction of COC <br /> mass in the source area. <br /> 8. ECM's capture analysis for the Industrial Avenue extraction and treatment system wells <br /> (EU-3 and EU-4) indicate that the actual capture zone is slightly larger in size than the <br /> capture zone predicted by the groundwater flow model. This suggests that the numeric <br /> groundwater flow model represents a conservative estimate of the hydraulic capture <br /> actually provided by EU-3 and EU-4 under in-field pumping conditions. <br /> 9. The current concentrations of COCs in the vicinity of the Stockton Avenue extraction and <br /> treatment system suggest that historically elevated COC concentrations in this area are <br /> no longer present. <br /> 5.4 MIGRATION CONTROL <br /> 10. The COC mass in the Upper and Intermediate aquifers appears to have decreased from <br /> 2008 to 2010, based on the extent and location of detected COCs in the Upper and <br /> Intermediate aquifers since 2007. <br /> 11. A downward vertical gradient exists between the Upper, Intermediate and Lower <br /> aquifers throughout the Study Area. This gradient is strongest at the groundwater <br /> mound beneath the City of Ripon WWTP; however flow from the overlying aquifers to <br /> the Lower Aquifer is prevented by the presence of the Corcoran Clay. <br /> 27 <br />