Application of Risk-Based Strategies and the Containment Zone Provision of the Regional Water Quality Control Board, San Francisco Bay Region to Implement the First Containment Zone for a Heavy Metal (Mercury) in California. R. M. Kalmes and D. B. Mathur, McLaren/Hart ChemRisk, 1135 Atlantic Avenue, Alameda, CA 94501
The California State Water Resources Control Board (SWRCB) under Resolution No. 92-49 has adopted a risk-based approach for the designation of Containment Zones for areas of groundwater where water quality objectives cannot reasonably be achieved. This resolution is implemented on a case-by-case basis by the Regional Water Quality Control Boards (RWQCBs). For the RWQCB to consider establishing a containment zone, various criteria must be adequately addressed including: 1) Adequate source removal and/or isolation to limit future migration of pollutants to groundwater; 2) An adequate understanding of the site, pollutant dynamics and hydrogeology ; and 3) An acceptable plan is submitted to the Agency for containing and managing the remaining human health and environmental risks, if any, posed by residual soil and groundwater pollution. Since its initial inception in 1994, the Containment Zone approach has been used by various Regional Water Boards to address problems associated with residual levels of organics in soil and groundwater. This presentation illustrates how this approach was applied to a site in Northern California located close to the Bay, that has mercury contamination in soil and groundwater, to establish the first containment zone granted by the RWQCB, San Francisco Bay Region for a metal in California. The project goal was to evaluate residual levels of mercury in soil and groundwater and use fate and transport modeling methodologies to ensure that cessation of the groundwater treatment system would have limited impact to migration of the groundwater plume and off-site health and environmental impacts. The cost-effectiveness of the on-going groundwater treatment system compared to the overall health and environmental risk-reduction implications for this Site will be presented. The presentation will highlight the use of interdisciplinary approaches, risk-based remedial alternatives, and recent risk-based regulatory initiatives for obtaining regulatory approval for site closures in a non-traditional and cost-effective fashion.