ARCHIVED REPORTS_MONITORING WELL INSTALLATION AND BIOSPARGE EVALUATION REPORT

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4.0 CONCLUSIONS AND RECOMMENDATIONS PSC drilled and installed wells CT-MW-8-87 and CT-MW-9-120 at the Site in June 2009. A ' third well installation was attempted near CT-MW-8-87, but no sandy permeable or saturated soils were encountered beneath 87 feet bgs and no well was installed. Soil samples from the well CT-MW-8-87 and boring CT-8-130 showed no detectable concentration except for minor concentrations of TBA from 45 to 81.5 feet bgs. Soil samples from well CT-MW-9-120 had minor concentrations of benzene and xylenes. Results of groundwater samples collected on July 22, 2009 indicate that groundwater in the well CT-MW-8-87 is impacted by TPH-g at 290 µg/L. Benzene concentration in this well was detected just above reporting limits. Minor concentrations of MTBE and TBA were also I detected. Groundwater samples collected on this date from well CT-MW-9-120 also indicated low level TPH-g and benzene concentrations. Minor concentrations of DIPE and TBA were also detected. Samples collected in October 2009 from these wells were similar ' except that benzene was not detected in well CT-MW-8-87 and TPH-g was not detected in well CT-MW-9-120. PSC agrees with the preliminary conclusion from Shaw made in the 2008 Pilot Test Report that the duration of the test was too short. In addition, it appears that injection pressures used during the second day of the pilot test may have fractured the soil and created preferential pathways. This would have affected results of additional testing during the treatability test conducted later. Therefore, PSC does not agree with the opinion that biosparging would have been an ineffective remedy for the Transmission Shop. The AS/SVE system used at the Former Dolly Madison site appears to be effectively removing petroleum hydrocarbons from the subsurface. The results of air sparging on this system has not yet been demonstrated. If the proper injection pressures and flow rates are used, air sparging should increase the effectiveness of the system. Baseline conditions for the Site appear to be conducive to implementation of the biosparging remedy. The stratified soil beneath the site complicates pilot testing, treatability testing, or implementation of this remedy. Testing should be performed in the "A" and `B" zones. Locations for testing should be selected in areas of significant "A" and `B" zone impact I where a sufficient number of monitoring wells are located. Care should be taken during testing to keep injection pressure at 5 to 10 psig above the breakthrough pressure calculated for the depth of the sparge point. tPSC still believes that biosparging will be an effective remedial alternative for petroleum hydrocarbons beneath the Site. PSC also believes this would be an effective remedial alternative for the commingled plume. This alternative should be considered by the commingled plume consultant and the technical committee after a SCM is completed. Monitoring Well Installation and BioSparge Evaluation Report Prepared For:Sara Lee Bakery Group,Inc. 20 Prepared By:PSC Industrial Outsourcing,LP Sara Lee—Lincoln Street 2009 12 03-MW Installation&BioSparge Evaluation Report(Final).doc Report Date:December 3,2009