RISK-BASED DECISION PROCESS FOR ACCELERATED CLOSURE OF A NUCLEAR WEAPONS FACILITY

摘要

Nearly 40 years of nuclear weapons production at the Rocky Flats Environmental Technology Site (RFETS or Site) resulted in contamination of soil and underground systems and structures with hazardous substances, including plutonium, uranium and hazardous waste constituents. The Site was placed on the National Priority List in 1989. There are more than 370 Individual Hazardous Substance Sites (IHSSs) at RFETS. Accelerated cleanup and closure of RFETS is being achieved through implementation and refinement of a regulatory framework that fosters programmatic and technical innovations: 1) extensive use of "accelerated actions" to remediate IHSSs, 2) development of a risk-based screening process that triggers and helps define the scope of accelerated actions consistent with the final remedial action objectives for the Site, 3) use of field instrumentation for real time data collection, 4) a data management system that renders near real time field data assessment, and 5) a regulatory agency consultative process to facilitate timely decisions. This paper presents the process and interim results for these aspects of the accelerated closure program applied to Environmental Restoration activities at the Site. Accelerated Action Program In 1996, DOE, EPA, and the Colorado Department of Health and Environment (CDPHE) (the Parties) executed the Rocky Flats Cleanup Agreement (RFCA). RFCA provides the regulatory approach and framework for the remediation of hazardous substance releases at the Site. In order to expedite remediation and maximize early risk reduction at RFETS, RFCA provides the framework for extensive use of accelerated actions to remove, stabilize, and/or contain IHSSs. A main feature of this framework is the reliance on a consultative process to streamline planning and reviews while achieving compliance with RCRA and CERCLA. Furthermore, RFCA requires the Parties to work together and fully involve the community in the decision making process for cleanup and closure of the Site. Risk-Based Screening Process As established in RFCA, RFETS is to be remediated to protect reasonably foreseeable land and water uses. In 1996, the foreseeable land use was open space and limited industrial. The Rocky Flats Wildlife Refuge Act of 2001 establishes Rocky Flats, upon cleanup and closure in accordance with RFCA, Colorado’s seventh national wildlife refuge. The Act provides that the Site will remain in federal ownership in perpetuity, and that jurisdiction of the Site will be transferred to the Interior Department to be maintained and protected as a refuge. This event coincided with discussions between the RFCA Parties and the community concerning the reevaluation of RFCA action levels for radionuclides in surface soils, I.e., the “interim cleanup levels” established in 1996. Since it is currently believed that the reevaluation will result in an agreement to lower the radionuclide surface soil action levels, this will result in removal of additional radionuclide surface contamination from the Site. In 1996, RFCA subsurface soil action levels merely adopted surface soil action levels as interim cleanup levels because a subsurface conceptual model for exposure pathways was not determined. These factors have resulted in development of a new risk-based screening process for assessing the need for, or extent of, accelerated actions for subsurface soil at IHSSs. The screening process compares contaminant concentrations in environmental media to Action Levels that are based on protection of a wildlife refuge worker surface user and ecological receptors for a wildlife refuge. Instrumentation for IHSS Characterization In order to facilitate data turnaround. The field program emphasizes use of an onsite laboratory and field portable instruments that generate real time data. Examples of instruments used on Site include gas chromatographs/mass spectrometers (GC/MS)), x-ray fluorescence (XRF) spectrometers, and high puri