ARCHIVED REPORTS_MONITORING WELL INSTALLATION REPORT 2010

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Monitoring Well Installation Report April 15, 2010 Former Nestle USA, Inc. Facility, Ripon, CA 7 GROUNDWATER ANALYTICAL RESULTS All of the groundwater samples collected from M-50A, M-51A, M-52B, and M-53B were maintained on ice until they were shipped by courier to TestAmerica's San Francisco environmental laboratory located in Pleasanton, California. This laboratory is accredited by the California Environmental Lab Accreditation Program (CELAP #2496). The samples were all analyzed for VOCs by EPA Method 8260B. Table 3 details the results of the laboratory analysis for the four monitoring wells, which were sampled at discrete intervals during installation in December 2009. All analytical laboratory reports are provided in Appendix E. 7.1 ANALYTICAL RESULTS FOR UPPER AQUIFER A-ZONE WELLS; INDUSTRIAL AVENUE The boring for M-50A was advanced at an approximate distance of 20 feet to the north of the location of an earlier boring, B-2, which was drilled in May 2007 (Figure 3). Boring B-2 was drilled to a depth of 47 feet bgs, where a sample was collected. The sample results from B-2 indicated a TCE concentration of 310 µg/L in 2007. A correlating sample, collected from the M-50A borehole at a depth of 45 to 46 feet bgs, had a TCE concentration of 28 pg/L (Table 4 and Figure 4a). Similarly, M-51A was installed an approximate distance of 20 feet to the northeast of a 2005 CPT boring CPT-1 (Figure 3) which had a concentration of TCE at 3,300 µg/L from a depth of 51 to 54 feet bgs in 2005. The results of a sample collected from boring M- 51A at a depth of 55 feet bgs showed a concentration of TCE at 3.3 µg/L (Table 4 and Figure 4b). The analytical results from M-50A and M-51A indicate that pumping by the Industrial Avenue IRAP Treatment System has had a successful remedial influence on Zone A of the Upper Aquifer, based on the low-levels of TCE in these samples, as compared to the samples collected from B-2 and CPT-1 in 2007 and 2005, respectively. 7.2 ANALYTICAL RESULTS FOR UPPER AQUIFER B-ZONE WELLS; STOCKTON AVENUE Figure 5 illustrates the upper aquifer wells located at the Stockton Avenue location, including new wells M-52B and M-53B. Depth-discrete samples collected from wells M- 52B and M-53B were selected to determine if concentrations of TCE and other COCs in the B-Zone have been sufficiently reduced to justify shutdown of the Stockton Avenue extraction well E-2. The laboratory results for these samples (Table 3) show low-level TCE concentrations ranging from 0.68µg/l_ (40.5 feet bgs in M-52B) to 10 pg/L (40.17 feet bgs in M-53B). Additionally, these sample results contained low-level cis-1,2- dichloroethene (cis-1,2-DCE) concentrations ranging from <0.50 µg/L to 2.4 µg/l_ (40.17 feet bgs in M-5313). No other COCs were detected in the six samples collected at the 519 South Stockton Avenue site. The results of these data can be compared to other B-Zone wells, as illustrated in Table 5 and Figure 6. These results indicate that the Stockton Avenue Treatment System (well E-2) is effectively remediating the area in the vicinity of these two new well locations. Historic data for well M-813, dating back to 1999, show a decreasing trend for TCE over time, as illustrated on Table 6 and in Figure 7. This decrease coincides with the installation and operation of extraction well E-2, suggesting that it has successfully 8