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I ' 4. EVALUATION OF REMEDIAL ALTERNATIVES In the Request for No Further Remedial Action Report (ETIC 2001), an evaluation of remedial alternatives was presented to address site conditions and natural attenuation was proposed as the remedial alternative for the site A summary of remedial actions conducted at the site to date and a risk analysis were also presented In a letter to ExxonMobil dated 27 January 2003, the SJCEHD (1) denied the request of no further remedial action "based upon nsk-based corrective action (RBCA) analysis", (2) requested additional groundwater cleanup, and (3) requested vertical assessment of the hydrocarbon-impacted groundwater In a meeting with representatives from ETIC, the SJCEHD, and the RWQCB on 17 Apn12002, ozone sparging was suggested as a remedial alternative by a representative of the RWQCB Additional investigation to vertically assess hydrocarbon impact to groundwater is presented in Section 3 A more detailed evaluation of remedial alternatives inclusive of ozone, excavation, enhanced bloremediation, steam stripping, and dual-phase extraction is presented below I4.1 REMEDIAL GOALS AND OBJECTIVES Based on the California Code of Regulations (CCR), Title 23, Division 3, Chapter 16, Section 2725(g)(1), Corrective Action Plans for waters with current or potential beneficial use must propose Federal and State maximum contaminant levels (MCLS) as cleanup goals These levels are based on the unlikely scenario of an onsite receptor that would use or drink the groundwater � . beneath the site Given the current land use in the vicinity of the site, groundwater development for potable supply is unlikely to occur in the near future Additionally, the experience of the environmental industry during cleanup efforts has shown that MCLS may not be economically or technically attainable with the technology currently available This is especially true for this site due to the mass of hydrocarbons that is present in fine-grained soil below the current groundwater level Typically, mass removal rates of groundwater remediation reach asymptotic levels prior to reaching MCLs As indicated by the monitoring results of SVE/AS and UVB remedial efforts already conducted, asymptotic levels were reached by remedial efforts If asymptotic levels are reached during the proposed remedial effort, further active remediation may not significantly change groundwater concentrations at rates any greater than natural processes Thus, if asymptotic mass removal rates of the proposed groundwater remedial alternative are reached prior to achieving BTEX MCLS, a risk management plan will be prepared The remedial goals and objectives for this project are (1) continued mass reduction of hydrocarbons in the subsurface and (2) continued control of the downgradient migration of dissolved phase hydrocarbons 4.2 SCREENING CRITERIA FOR CORRECTIVE ACTION ALTERNATIVES The selection of an appropriate remedial alternative for corrective action at the site is based on evaluation of the following criteria f II Cr\Prgects173942WASTER\WP1WP03031V;Nx d« 13