SITE INFORMATION AND CORRESPONDENCE

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CLEANUP AND ABATEMENT ORDER NO. R5-2006-0720 NESTLE USA, INC. RIPON, SAN JOAQUIN COUNTY these new wells. Additional monitoring wells need to be installed in the Lower Aquifer Zone to provide early detection of plume migration towards these supply wells. 12. Based on historical monitoring in the Upper and Intermediate aquifer zones beneath the Facility, TCE,cis-1,2-dichlorethene,vinyl chloride, and chloroform are the primary VOCs detected in groundwater. Other constituents of concern detected in groundwater beneath the Facility include tetrachloroethene, 1,1,1-trichloroethane,trans-1,2-dichloroethene, 1,1-dichloroethene, 1,2- dichloroethane, 1,1-dichloroethane, methylene chloride,carbon tetrachloride, and bromoform. Carbon tetrachloride and tetrachloroethene appear to originate from sources not associated with the Discharger. On 4 April 2006,the Discharger submitted the Draft 2005 Annual Groundwater Monitoring Report. Concentrations of VOCs have generally declined one to two orders of magnitude in most monitoring wells since discovery of the release in 1985. However,the plume has spread laterally and vertically since 1985 and recent vertical profiling of the Upper Aquifer Zone discovered residual concentrations of TCE as high as 7,800 µg/L in the Industrial Avenue source area(Geomatrix 2006). Maximum concentrations of VOCs in the Discharger's groundwater monitoring wells (Figure 3)in 2005 are presented in the table below: Constituent Concentration Trichloroethene 590 Cis-1,2-dichloroethene 250 Vinyl Chloride 220 Chloroform 12 Tetrachloroethene 2.2 1,1,1-Trichloroethane 0.16 Trans-1,2-dichloroethene 4.1 1,1-Dichloroethene 3.4 1,2-Dichloroethane <0.5 1,1-Dichloroethane 6.5 Methylene chloride 0.52 Bromoform 2.3 13. The Discharger has monitored local supply wells since 1986. VOCs,principally TCE and cis-1,2- DCE, have been detected in existing municipal supply wells MW-7 and MW-9. Concentrations of these VOCs have exceeded California Primary Maximum Contaminant Levels (MCLs) in MW-9. In 1998,the City of Ripon installed a granular activated carbon(GAC) unit on MW-9 to treat VOCs originating from the Discharger's former facility. Concentrations of TCE in well MW-7 have exceeded the California Public Health Goal (PHG),but have been below the MCL. TCE and/or cis- 1,2-DCE have also been detected in former municipal wells MW-1 and MW-6 and former Simpson Paper Company production wells PW-04 and PW-05,but use of these wells was discontinued for reasons unrelated to the TCE plume. 14. In 1990,the Discharger submitted a Draft Risk Assessment that evaluated the degree of risk to human health posed by the groundwater TCE plume. At the time that report was submitted,the Discharger believed that the TCE plume had not migrated far from the Facility and the report concluded that there was no complete pathway to potential receptors including the local municipal supply wells. 4