ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study is provided in the Interim Remedial Action Plan, Well Installation and Aquifer Test Report" and the Interim Remedial Action Plan Groundwater Extraction System Startup Report' In response to an increase in TCE concentrations detected at monitoring well M- 1 OA (located approximately 1,000 feet northwest of the Site), Nestle conducted a Cone Penetrometer Test (CPT) investigation in September 2010. The purpose of the CPT investigation was to assess the groundwater conditions to better understand the concentration trends at well M-10A". After the results of the CPT investigation were reviewed, it was concluded that groundwater extraction at well EI-1 had curtailed the movement of TCE-affected groundwater onsite and near the Site in the lower A-zone, when operating at rates greater than approximately 25 gallons per minute (gpm). Therefore, extraction and treatment of groundwater from well EI-1 (screened in the lower A- zone at approximately 100 to 120 feet bgs) resumed in November 2010 at approximately 90 gpm. Nearby monitoring wells and influent concentrations are monitored to assess the effectiveness of pumping from well EI-1 and to monitor the trend in well M-1 OA. Investigation and modeling analyses performed in 1999 indicated that groundwater pumping would control plume migration in the Upper Aquifer"" near the area of 519 South Stockton Avenue. These findings led to the installation of extraction well E-2 at 519 South Stockton Avenue in 1999. The Upper Aquifer extends to an average depth of approximately 110 feet bgs, and will be further discussed in Sections 4.2 and 6.2Xv". Based on declining and reduced COC concentrations at wells E-2 and E-6, RWQCB approved the shut-down of the remediation system at 519 South Stockton Avenue in October 2010. In 2001, a numerical groundwater model was developed to assess the movement of groundwater in response to pumping, based on an earlier Site Conceptual Model (SCM) and historical water use scenarios. Based on the modeling results from 2001, extraction well E-6 was installed in 2002 in the Intermediate Aquifer, and constructed with well screen from 143 to 158 feet bgs. The Intermediate Aquifer underlies the Upper Aquifer. The base of the Intermediate Aquifer is the Corcoran Clay which is encountered at an average depth of 196 feet bgs and slopes westward beneath the Study Area, as discussed in Sections 4.2 and 6.2. Extraction well E-6 was subsequently added to the extraction system at Stockton Avenue (E-2) in 2004. This extraction well was designed to extract at a maximum rate of 600 gpm. However, extraction did not begin at this well until mid-2004 due to volume and TDS concentration limits imposed by the City of Ripon for the discharge of treated groundwater to the municipal industrial sewer system. The discharge permit issued by the City did not allow 600 gpm of water discharge into the WWTP due to RWQCB limitations upon the City. Instead, the treated groundwater from E-2 and E-6 was discharged to the City of Ripon's non- potable (NP) water system for beneficial use. Beneficial use includes using the discharge for make-up and non-contact cooling water at a power co-generation facility, irrigating parks, and groundwater recharge. 6