ARCHIVED REPORTS_2003 FEASABILITY STUDY REPORT AND SITE ASSESSMENT WORK PLAN

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S E C O R 2003 Feasibility Study Report and Site Assessment Work Plan July 18, 2003 Page 17 continue around the northern-most property corner (near well MW-50B) and end along the northeast property line (near well MW-51 A). Pumping wells would be approximately 30 feet deep and placed every 50 feet on center for a total of twenty wells. Submersible pumps with level controls would be installed in the wells to maximize continuous groundwater drawdown. Extracted groundwater would be treated on-site via a carbon treatment system designed to handle approximately 180 gallons per minute. Recovered groundwater would initially enter a forwarding tank to capture sediments and allow batch treatment. During batch treatment, electric forwarding pumps would transfer groundwater through a series of bag filters (to remove finer sediments) and through a series of granular activated carbon canisters for final treatment. Treated groundwater would then be discharged to the storm drain or sanitary sewer under an appropriate permit. A process flow diagram of the hydraulic control line is presented as Figure 8. Semi-annual off-site groundwater sampling would be conducted to evaluate compliance with the Basin Plan's WQOs. 6.3 Combination Groundwater Barrier and Hydraulic Control Line This alternative consists of a subsurface low-permeable wall and a series of pumping wells used to function as a hydraulic control line (Figure 2). The groundwater barrier in this alternative would act as a groundwater deflector to direct groundwater to a location where pumping wells are placed. The pumping wells would then extract groundwater and deter or prevent the migration of hydrocarbons beyond the property line. The barrier wall would be approximately 800 feet long, 30 feet deep and 12 inches wide. The barrier wall would extend from the northwest property line (near well MW-47A), continue around the northem-most property corner (near well MW-50B) and end along the northeast property line (near well MW-19A). Installation of the barrier wall could be accomplished as described in Section 6.1. The hydraulic control line would be approximately 200 feet long and extend along the northeast property line from well MW-19A to well MW-51A. Pumping wells would be approximately 30 feet deep and placed every 50 feet on center for a total of four wells. Submersible pumps and level controls would be installed in the wells as described in Section 6.2 and extracted groundwater would be treated on-site via a carbon treatment system designed to handle approximately 36 gallons per minute. Recovered groundwater would initially enter a forwarding tank to capture sediments and allow batch treatment. During batch treatment, electric forwarding pumps would transfer groundwater through a series of bag filters (to remove finer sediments) and through a series of granular activated carbon canisters for final treatment. Treated groundwater would then be discharged to the storm drain or sanitary sewer under the appropriate permit. A process flow diagram of the groundwater barrier and the hydraulic control line is presented as Figure 9. Semi-annual off-site groundwater sampling would be conducted to evaluate compliance with the Basin Plan's WQOs. 6.4 Groundwater Oxygenation System This alternative consists of installing groundwater oxygenation points in series to create and oxygen- enriched zone along the terminal property line (Figure 2). These groundwater oxygenation points would be used to increase dissolved-oxygen concentrations in the saturated zone and enhance the I:\Chevron\1001621\REPORTS\2003\2003FS\FS 2003 revD.doc