MARSSIM (?) Final Status Survey Approach for Soils at the Rocky Flats Closure Project

E.W. Abelquist (Oak Ridge Associated Universities)

The Rocky Flats Environmental Technology Site (RFETS) is a Department of Energy (DOE) facility located northwest of Denver, CO. RFETS was operated until 1992 as a nuclear weapons research, development and production complex, and is currently being remediated under a DOE closure contract. The Rocky Flats Closure Agreement (RFCA), which specifies a release criterion for plutonium in surface soils, has driven extensive soil sampling campaigns in both the industrial area and buffer zone based on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Recently, the DOE requested the Oak Ridge Institute for Science and Education (ORISE) to perform independent verification of the cleanup contractor's final status survey design and implementation at RFETS. ORISE recommended that the final status survey be designed following the MultiAgency Radiation Survey and Site Investigation Manual (MARSSIM) approach. In general, the final status survey generates data that address two compliance conditions: 1) the average soil contamination level across a survey unit meets the release criteria, and 2) any hot spots satisfy elevated measurement release criteria. The MARSSIM effectively addresses these conditions through classification of areas, statistical sample size determination, and scanning to identify potential hot spots. The cleanup contractor evaluated the existing CERCLA soil sampling data and concluded that it sufficiently satisfies the MARSSIM data needs for a final status survey. To address hot spots that may be present, the contractor is investigating the efficacy of integrating conventional scanning using a thin crystal sodium-iodide (NaI) detector with site-wide scanning techniques. MARSSIM's flexibility in handling existing CERCLA-based sampling data will be illustrated with examples from survey units in both the industrial area and buffer zone.

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