ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study Groundwater extraction and treatment activities at the Site and at 519 South Stockton Avenue have resulted in the discharge of approximately 1.4 billion gallons of water between 2000 and 2009. These activities removed an estimated 1,286 pounds of CDCs between 2000 and 2009, equivalent to 0.87 pounds of COCs per every million gallons of groundwater pumped. Figure 4 and Figure 5 summarize the historical mass removal rates at the Stockton Avenue and Industrial Avenue treatment systems. The detection of COCs in groundwater samples collected from two private (domestic) water wells south of the River in 2005 has been addressed with additional characterization, well replacement and wellhead treatment. Immediately following this discovery, bottled water was provided to the residents of the impacted domestic wells. Soon after, wellhead treatment systems were installed at each affected well. As of the date of this Revised FS Report, one water replacement well has been installed at one residence and another well is targeted for installation in November 2009. 3.4.3 Source Area Remediation Even though multiple SVE and groundwater extraction and treatment systems have operated since 1989, potential residual source areas with elevated COCs may continue to impact groundwater beneath the Site. Pilot tests of multiple technologies were conducted to assess additional mass removal from the source areas northeast of the Site (near the extraction wells EI-1 and EW-1, and monitoring wells M-1A and M-113). These included injection of microbes and nutrients in 1989"', potassium permanganate in 2000"" and a carbohydrate substrate (molasses) in 2005X"' Very little information is available about the 1989 pilot test of injected microbes and nutrients, although the 1994 FS indicated in-situ bioremediation may be effective. In August 1999, potassium permanganate was injected in four locations at three depth intervals in the Upper Aquifer. Since no hydraulic mixing was observed initially, pumping from three extraction wells in various configurations was introduced to enhance mixing. This allowed permanganate to reach impacted groundwater approximately 20 feet from the injection points. Though TCE oxidation was observed in all seven monitoring wells, and cis-1,2- dichlooroethene (cis-1,2-DCE) oxidation occurred in six of the wells monitored, concentration rebound occurred in most wells within 28 weeks"" A detailed assessment of this potassium permanganate injection study is included in Attachment A.1. The most recent in-situ biodegradation test, performed in 2005, indicated half- lives associated with carbohydrate utilization at approximately 20 days". The test showed the transformation of TCE to cis-1,2-DCE, although complete breakdown of TCE to ethene was not observed during the 30-day test. Results also showed increases in selenium and arsenic in groundwater above background levels, with concentrations returning to background levels after 30 to 7