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: '�'-Oeasibility Study—Enhancement of Existing Remediation Activities 8200 N. Highway 99, Stockton, CA Page 4 of 10 2.0 FEASIBILITY STUDY 2.1 Remedial Alternatives Selected for Evaluation The remedial alternatives that were evaluated for enhancing cleanup of groundwater near MW12 include additional groundwater extraction and in-situ chemical oxidation (1SCO). The criteria used to evaluate potential remediation enhancement options for the site include technical feasibility, implementation issues, effectiveness, cost and public acceptance. 2.2 Description of Alternatives The following alternatives for the site have been considered: • Alternative 1 Groundwater Extraction • Alternative 2 In-Situ Chemical Oxidation 2.2.1 Alternative 1 - Groundwater Extraction and Treatment This alternative would involve adding an additional groundwater extraction well (EW3) approximately 30 feet southwest of MW12. The new extraction well would be tied into the existing subsurface infrastructure that connects EW2 to the GETS. Treatment of the extracted groundwater is ongoing and the existing system consisting of an air stripper and three 2,000-pound carbon treatment vessels can accommodate the additional extraction well. 2.2.3 Alternative 2—In-Situ Chemical Oxidation This alternative would involve the injection of a strong oxidizer%into the affected aquifer material. The oxidizer will attack organic compounds ultimately-mineralizin 7 them into water and carbon dioxide. Ozone injection has been shown to be effective in oxidizing organic contaminants such as fuel hydrocarbons and can be inexpensive to operate after the initial costly installation phase. A series of ozone injection wells trending northwest to southeast located southwest of MW12 would create an ozone barrier that will likely destroy fuel hydrocarbons as groundwater moves through the "ozone curtain". This alternative is feasible from a technical standpoint; however the effectiveness would be based on the volume and rate of contamination passing through the ozone curtain. The curtain may prevent increasing concentrations from reaching the area around MW 12, but additional injection points around MW12 would be required to treat contaminants already impacting the area. In addition, the elevated costs of the required bench scale testing, equipment purchases, injection well installation, and subsurface infrastructure make this alternative economically restrictive. Rather, this alternative would be worthy of consideration in targeting the source area where the mass of contaminants is concentrated in a relatively limited volume of aquifer material. The alternative may be considered for enhancing remediation in the former tank pit if the evaluation of soil confirmation samples indicates additional remediation is needed in the source area. G:IGROUNDZEATULEBURGIReports10709 FS rem enhancement.doc