Applying Cost-Benefit Analyses to the Cleanup of a Department of Energy Mixed Waste Site. M. MacDonell, J. Peterson, L. Haroun, D. Blunt, and D. Dunning, Argonne National Laboratory, Environmental Assessment Division EAD1900, 9700 South Cass Avenue, Argonne, IL 60439
As taxpayers are increasingly aware of the need to balance tradeoffs in financing the enormously expensive Federal cleanup program, the importance of explicitly considering what benefits can reasonably be achieved at these contaminated sites using the finite resources available has become even more obvious. Reducing exposures to levels as low as reasonably achievable (ALARA) is a cornerstone of the Department of Energy's radiation protection program. This process is currently being applied to develop cleanup levels for the Department's contaminated sites across the country, many of which are mixed waste sites. Under the ALARA process, exposures and risks are reduced as far below protective criteria as can reasonably be achieved-- considering technical, economic, and social factors. The process includes both a planning component (the assessment and decision-making phase) and a field component (the implementation phase during which contaminants are removed). Risk-based cleanup levels have been developed and are being implemented for surface water and soil at a DOE mixed waste site in Missouri, following explicit applications of the ALARA process. Factors considered include: (1) capital and operation and maintenance costs of various treatment system configurations to achieve incremental (risk-based) contaminant concentrations in water discharged to a source of local drinking water; (2) requests from State officials and the community regarding technical components of the operating, discharge, and monitoring plans for the water treatment system; (3) the feasibility and cost of field versus laboratory analyses for verification of contaminant removal from soil; (4) incremental costs and risks associated with excavating and handling increased soil volumes to achieve lower residual contaminant levels; (5) "replacement risk" implications associated with concentrations of naturally occurring metals and radionuclides in local soil used to backfill excavated areas; and (6) stakeholder issues regarding future land use. Results for this site indicate the success of the ALARA field application, as contaminant concentrations are lower than the limits agreed to with the State, EPA, and community. Post-cleanup surveys at other DOE sites have also demonstrated that the residual levels achieved are routinely lower than the limits established during the decision-making stage. Lessons learned include the importance of (1) conducting site-specific ALARA analyses (because contaminant types and distributions, appropriate exposure scenarios, local conditions, and constraints will vary) and (2) maintaining a distinction between the planning and field components (because hard-wiring ALARA goals for field operations into the planning process can negate the intended outcome, leading to over-designed remedies that achieve little further risk reduction for substantially higher costs).