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 remediated the areas near new wells M-52B and M-5313, based on the low-level TCE concentrations observed in these new wells. 7.3 ANALYTICAL RESULTS FOR OFF-SITE WELL M-54C Monitoring well M-54C was sampled using PDB sampling technology on January 18, 2010. The analytical results are provided on Table 7 and the laboratory analytical report is provided in Appendix E. Groundwater in this area is locally affected by recharge and discharge areas, and generally flows away from recharge areas, including the City of Ripon municipal lagoons. In all four quarters of 2009, high groundwater elevations in the Intermediate Aquifer were observed due to mounding in the recharge area, affecting wells such as M-17C1 and M- 20C1, which are located north of the lagoons. As a result of the effects of this recharge area, groundwater flows to the north from the lagoons, towards the Stockton Avenue site. Therefore, it is expected that concentrations observed near the lagoons (M-17C1 and M-20C1) would have trend moving north and away from lagoons towards the Stockton Avenue site. Table 8 and Figure 9 provide a comparison of COC data for wells located in the vicinity of the Stockton Avenue site and the municipal lagoons. 8 CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations may be drawn from the data collected from the field activities associated with the installation of wells M-50A, M-51 A, M-5213, M- 53B, and M-54C: INDUSTRIAL AVENUE SYSTEM • The purpose of installing two groundwater monitoring wells within the A Zone at the 230 Industrial Avenue site was to evaluate the eastern and western extents of the capture zone of the Industrial Avenue IRAP Treatment System wells EU-3 and EU-4. In order to conduct the proposed capture zone analysis, a temporary shutdown of the system will be necessary to collect static water level data in the vicinity of the system. Details of the proposed system shutdown, monitoring and sampling during the shutdown, and post-shutdown monitoring, will be documented under separate cover The discrete groundwater samples collected from wells M-50A and M-51A indicate the presence of low levels of TCE within the area of influence of the Industrial Avenue IRAP Treatment System. Groundwater samples collected from borings advanced in 2005 and 2007 exhibited much higher TCE concentrations, as illustrated in Table 4. The reduction in localized TCE concentrations indicates that the Industrial Avenue IRAP Treatment System is operating efficiently and has been successful in removing COC mass from the area targeted by the treatment system. Stockton Avenue System • The purpose of installing two groundwater monitoring wells within the within the B Zone beneath the Stockton Avenue site was to determine if concentrations of 9