SITE INFORMATION AND CORRESPONDENCE_3

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Mr. Mike J. Infurna Jr. '' Del MbrIfe Foods—Former Disco Site December 19, 2008 Page 3 of 4 Stockton, California Onsite Soil Vapor Extraction System Shutdown The current SVE treatment system consists of five soil vapor extraction wells (SVE-1 through SVE-5). Locations of the SVE wells are included on Figure 2. SGI proposes shutdown of the SVE system while data is collected and a final remedial approach is developed for the Site. As reported in the Third Quarter 2008 Groundwater Monitoring Report, dated October 31, 2008, the SVE treatment system is removing little to no mass of contamination from the source area. The SVE Rebound Assessment Report, dated July 28, 2008 concluded that very little to negligible amounts of contamination remain in the vadose zone in the source area and soil vapor extraction influent concentrations have reached asymptotic levels. Soil vapor extraction influent concentrations over time is provided as Figure 4. As approved by SJCEHD, the SVE system is currently only operating 1 day per month. SGI proposes to discontinue the one day per month operation of the SVE treatment system. During the development of the updated conceptual site model, SGI will collect confirmation soil samples from the vadose zone, to determine if additional vadose zone remediation is necessary. Onsite Air Sparae System Modification The current AS treatment system consists of six dual nested AS wells (AS-1A/B through AS-5A/B, NP-1-70, and NP-1-90), conveyance piping, air compressor, and control panel. The existing onsite air sparge treatment system will be modified to operate as a biosparge system. The air flow into the subsurface will be reduced to approximately 2 standard cubic feet per minute per well, which will promote natural biodegredation of petroleum constituents in groundwater, while minimizing the risk of inducing lateral migration of the plume. Summary SGI proposes immediate shutdown of the existing ozone sparge and SVE systems, and modifications to the AS system. Monitoring wells will continue to be monitored and sampled on a routine basis as outlined in the December 5, 2001 Groundwater Monitoring Frequency Decision Tree. A work plan to fulfill data gaps in the conceptual site model and address San Joaquin County Environmental Health Department (SJCDEH) comments in the February 25, 2008 correspondence will be submitted to the SJCDEH by January 15, 2008. The Source 6fe00,Inc.