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Mr. James Barton November 2, 2004 Page 2 treatment technologies to help control plume movement and achieve the ultimate goal of site closure. The anticipated completion date for the RSE is November 30, 2004. 2. Conduct a comparative analysis of the changes in contaminant concentrations and distribution and mass within the aquifer beneath the site. Temporal changes will be evaluated beginning with the start of active remediation in October 1999. Estimates of changes in contaminant mass and distribution will be evaluated in light of the original goals of the remedial system. Recent groundwater monitoring results indicate reductions in contaminant mass now that the air sparging system has been overhauled and restarted and the highest residual concentrations are in a localized area around MW-11. The anticipated completion date for the comparative analysis is November 30, 2004. 3. Install additional monitoring wells into the lower two water zones (Unit C and Unit D) to further define the vertical and lateral extent of contaminants in those units and the groundwater flow direction relative to the upper units. The work plan for the proposed wells (MW-31 and MW-32) is included in this document. Pending approvals from the site owner, RWQCB and San Joaquin County Environmental Health Department (SJCEHD), well installation activities should begin prior to November 19, 2004. 4. Beginning in fourth quarter 2004, groundwater parameters related to intrinsic biodegradation, specifically, concentrations of nitrates and sulfates by EPA Method 300, iron (II) by Standard Method 3500 Fe D, manganese (II) by EPA Method 200.7, and methane EPA Method RK will be analyzed in wells MW-2, MW-4, MW-7, MW-8D, MW-11, MW-14, MW-16 and MW-27. Dissolved oxygen readings will also be collected from wells MW-2, MW-4, MW-7, MW-8D, MW-11, MW-14, MW-16, and MW-27. Selected wells were chosen due to there proximity to the axes approximating the plume centerline and along a transverse axes. The results will be plotted on radial redox diagrams as a visual aid in analyzing natural attenuation within the boundaries of and at the outer edges of the plume. These analyses will also be utilized in evaluating the appropriate response to fluctuating concentrations at the plume boundaries. 5. Depending on the results of the forthcoming Geochemical Evaluation (GE), conduct bench- scale and pilot-scale tests of in situ chemical oxidation using ozone. The studies will evaluate the potential for ozone to be used to effect in situ contaminant mass destruction without adverse impacts to the aquifer. Alternative oxidants may also be evaluated during the bench-scale study. The GE evaluation will be submitted to the RWCQB on or before November 15, 2004. During a conversation between Ben Heningburg and Jim Barton on October 15, 2004, Mr. Barton stated that, based on preliminary soil analytical results for chromium, a bench-scale study would be required. 6. Submit a Corrective Action Plan (CAP) or work plan that includes a feasibility study of alternative remedial technologies that may accelerate contaminant reductions and eventual site closure. Technologies will be evaluated for their ability to achieve remedial goals within an accelerated time frame at a minimal or reasonable cost. Also, the need for active control J:\Projects\06940\5098-293\FinalRReports\Work Plans\5098 Work Plan-SVE AS System.doc