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M <br /> GA-ROVERS Mr. Michael Inf lima <br /> & ASSOCIATES November 26, 2008 <br /> permit conditions and the limitations of carbon treatment for TBA, Shell determined that an <br /> upgrade or expansion of the current carbon treatment system would not ensure permit <br /> compliance. Several alternative remedial technologies were considered for this site prior to <br /> selecting IS CO. ISCO was selected over the other alternatives based on feasibility (technical and <br /> practical), effectiveness, agency acceptance, permit compliance, and to a lesser extent cost, <br /> FINAL REMEDIATION PLAN <br /> I <br /> Site Cleanup Objectives <br /> Site cleanup objectives are typically based on one or more of the following criteria: <br /> • Department of Health Services primary or secondary maximum contaminant <br /> levels (MCLsy for drinking water, <br /> • Regional Water Quality Control Board (RWQCB) established water quality <br /> objectives (WQOs). <br /> • Environmental Screening Levels established by the San Francisco Bay region - <br /> RWQCB 's risk-based corrective action (RBCA) guidelines, <br /> • Risk-based clean-up levels established by risk assessment or RBCA analysis, <br /> • Current closure guidelines from the regulatory agencies, such as the California <br /> State Water Resources Control Board criteria for low-risk groundwater cases, or <br /> • Application of Best Available Technology based on remediation system <br /> operation data that demonstrate asymptotic levels have been achieved for <br /> chemical concentrations in soil and/or groundwater. <br /> Groundwater Cleanup Levels <br /> The RWQCB 's Water Quality Control Plan (Basin Plan) for the Central Valley states that <br /> existing and potential beneficial uses applicable to groundwater in the region include: municipal <br /> and domestic water, agricultural, industrial services, and industrial processes. Table A presents <br /> the constituents of concern (CDCs), background levels, established water quality objectives <br /> (WQO's) based on the drinking water maximum contamination levels (MCLS) defined in section <br /> 22 of the California Code of Regulations (CCR 22� highest historical concentrations at the <br /> subject site, and current maximum concentrations at the subject site (using July 2, 2008 <br /> monitoring well data), <br /> 240783 2 <br /> Worldwide Engineering, Environmental, Construction, and IT Services <br />