Utilization Of The MARSSIM Approach To Deep Excavations And Backfill Areas
W. D. Vogel, A. J. Nardi
In some instances a remediation effort will involve either the excavation of burials that were previously authorized by either regulation (or a specific approval) or the excavation of soils that have been contaminated at depth due to other physical processes. In such cases, the resulting excavation may involve the removal of overburden material prior to the excavation of the horizon of contaminated material. The overburden material and the residual soil beneath the original horizon of contaminated material may or may not contain residual radionuclides in excess of the levels found in the general background. The resulting excavation would then be backfilled with possibly a combination of clean, off-site borrow material and of overburden material that was removed during the excavation phase. Because the overburden material is potentially contaminated, a final status survey protocol would be necessary that goes beyond the scope of MARSSIM guidance. The U.S. Nuclear Regulatory Commission has partially addressed this issue in the guidance given in the Appendix E of the NMMS Decommissioning Standard Review Plan (NRC 2000b). However, that discussion is based on the premise that the subsurface volume of contaminated soil will be left in place rather than being excavated and having some fraction of the excavated soil returned as backfill as is the case being discussed in this paper. Thus this guidance is only partially applicable to the case at hand. The following is the description of an approach that could be used during the excavation of subsurface contamination that meets the intent of a MARSSIM based final status survey.
This abstract was presented at the 35th Annual Midyear Meeting, "Decommissioning and Environmental Restoration", MARSSIM 2 Session, 2/17/2002 - 2/20/2002, held in Orlando, FL.