ARCHIVED REPORTS_MONITORING WELL M-10 INVESTIGATION REPORT 2010

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M-10A Investigation Report November 30, 2010 Nestle USA, Inc., Ripon, California increase in TCE concentrations observed in groundwater samples from monitoring well M-10A; and • Secondary pathways or sources to the west, such as possible sources or pathways near the location of Regal Almond, are also likely present based on the spatial TCE distribution. ECM recommends the following: • Restart on-Site groundwater extraction at well EI-1 (Section 6); • Evaluate the capture zone based on new water levels and historical hydraulic testing data from well EI-1 data;15 • Continue monitoring COC concentrations in well M-10A and report the findings in the Annual Groundwater Monitoring Report. 6 REMEDIAL MEASURE Following completion of fieldwork, ECM and AMEC Geomatrix jointly evaluated the current and historical information to determine the cause of the increase in COC concentrations in well M-10A. Based on the evaluation, ECM recommended commencing extraction of groundwater from well EI-1 at the Site as soon as possible. On Thursday, October 28, 2010, ECM contracted Howk Systems (Howk) to place a 10 horsepower pump (formerly used in well E-6) into well EI-1 (see Appendix D for boring log and well construction information). Howk surged the well with a vented surge block prior to installing the pump. ECM field technicians tested the pump, reconfigured the wiring, and balanced the flow rates from wells EI-1, EU-3, and EU-4, to maximize the pumping rate in well EI-1 and to retain 30 gallons per minute (gpm) in wells EU-3 and EU-4. At 4:00 PM on Friday, October 29, well EI-1 began running at 90 gpm concurrently with wells EU-3 and EU-4, each running at 31 gpm, for total A-zone groundwater extraction of 152 gpm. Wells EI-1, EU-3 and EU-4 continue to operate at these rates as of the date of this report. To facilitate the evaluation of the effectiveness of extraction at EI-1, ECM measured water levels in nearby monitoring wells. Field personnel measured depth to groundwater water at monitoring wells EW-1, M-1A, M-47A, M-2A, M-6A, and EU-2 on Thursday, October 28, prior to initiating pumping at well EI-1 and on Tuesday, November 2, approximately 3 days after pumping resumed at well EI-1. ECM will continue monitoring the COC concentrations in M-10A and the efficiency of pumping at EI-1, evaluate the data, and report the findings in the Annual Groundwater Monitoring Report. 11