ARCHIVED REPORTS_2010 ANNUAL REPORT

Home Browse Search

Nestle USA, Inc., Ripon, California March 31, 2011 2010 Annual Report and EU-4, each running at 31 gpm. Wells EI-1, EU-3 and EU-4 continue to operate at these rates as of the date of this report. 4.1.2 PERFORMANCE MONITORING Water quality samples were collected from three locations, consistent with MRP requirements for monitoring: • The influent to the first in-series carbon vessel, • The midpoint on the piping between the second and third carbon vessels, and • The effluent after the final carbon vessel. The monitoring frequency at each location was revised in the 2010 MRP (Table 9.1). Currently ECM samples the influent and effluent locations quarterly and the midpoint location monthly. Historical TCE concentrations for extraction wells EU-3 and EU-4 (Table 3.1) are illustrated below. Industrial Avenue Extraction Well TCE Concentrations over Time 350 300 250 EU-3 0 200 EU-4 .2 R L 150 m c U 100 W 50 0 Mar-08 May-08 Aug-08 Nov-08 Mar-09 May-09 Aug-09 Nov-09 Mar-10 May-10 Aug-10 Nov-10 Sample Date The general decline of concentrations of TCE in EU-3 and EU-4 indicate that the areas of highest TCE impact, which were targeted as part of the IRAP, have undergone significant reductions in dissolved TCE concentrations. TCE concentrations in wells EU3 and EU-4 in July 2010 were 94% and 98% lower than the concentrations observed in the wells in March 2008. Mass removal rates have dropped from 0.60 pounds of TCE per day in the first quarter of 2008 to 0.03 pounds of TCE per day during the third quarter of 2010. Based on in-field monitoring and groundwater modeling of the Industrial Avenue area23, wells EU-3 and EU-4 appear to provide the intended hydraulic containment, as proposed in the Industrial Avenue Facility Interim Remedial Action Plan, Well Installation and Aquifer Test Report24. 21