ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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In October 2005, Geomatrix conducted in-situ push-pull tests at wells M-1A and M-1 B to evaluate carbohydrate utilization rates and assess potential changes in aquifer conditions due to the addition of carbohydrate. Geomatrix injected a carbohydrate solution (composed of molasses) and a conservative tracer (bromide) injected into the wells at target depth intervals, follow by ten extraction and sampling events. The transformation of TCE to cis-1,2 DCE was observed in well M-1 B, but not in well M- 1A. Complete breakdown of TCE to ethane was not observed in the 30-day test. Selenium and arsenic concentrations in groundwater increased above background levels. In some cases, these concentrations were above the MCLs. In-situ treatment using carbohydrate injection is not feasible for treating COCs in the groundwater at the Site at this time because: • observed increases of selenium and arsenic concentrations to above-MCL levels are of concern for any anaerobic ISB treatment approach, particularly given the presence of drinking water wells with the Ripon Study Area, and • a large increase in total dissolved solids is also anticipated. Attachment A.2 includes a detailed description and assessment of the previous in-situ carbohydrate push-pull test performed at the Site. 5 SOIL VAPOR EXTRACTION (SVE) ACTIVITIES AT INDUSTRIAL AVENUE SITE Vacuum extraction is an in-situ process that recovers VOCs from soil by enhancing volatilization of contaminants within the soils into the soil vapor. A vacuum is applied to the soil which propagates laterally from the extraction wells. Contaminant vapors and liquids migrate to the extraction wells where they are brought to the surface and treated prior to discharge. Camp Dresser & McKee (CDM) installed the first soil vapor extraction wells (VE-1 through VE-5) in 1986. A pilot SVE program was initiated to test the efficiency of the system in removing TCE from the vadose zones. The Site SVE system was expanded to include a total of eight vapor extraction wells in 1992. These additional wells focused on extracting vapors from TCE- and chloroform-impacted areas near suspected chemical releases on the eastern portion of the Site. In 1998, Fluor Daniel GTI (Fluor Daniel) installed four new SVE wells and a new vapor treatment system to focus vapor extraction activities in the area of highest remaining TCE concentrations near the former decaffeination building. An estimated 880 pounds of VOCs (primarily TCE and chloroform) were extracted from the subsurface between 1988 until the discontinuation of SVE prior to 1994. The historical SVE remediation activities have resulted in remediation of the vadose zone (within the upper portion of the B-zone beneath the Site) to extent feasible. Post- remediation investigations and soil vapor sampling in 2006 through 2008 in the area of the Site confirm the lack of soil vapor impacts in shallow soil gas samples, above levels of concern with regard to indoor air exposure levels for commercial/industrial property. SVE would not be effective as a groundwater treatment technology for the Site because VOCs below the water table would have to move by diffusion to the water table interface 4