What investigations were performed on the IWCS as part of the NFSS remedial investigation?
No direct sampling through the protective clay cap or side clay cut-off walls of the IWCS was performed to ensure that the integrity of this protective layer was not breached. The IWCS cap was designed and is maintained to ensure that it properly retards radon emissions and inhibits infiltration of water (in the form of precipitation) that would enhance leaching of contaminants into groundwater. However, two types of evaluations (in addition to a thorough document review of historic waste inventories and past waste management practices) were performed to assess the continued protectiveness of the cap. • A multi-technology geophysical walk over, which used non-intrusive techniques to infer the condition of the subsurface below the cap. • A site-specific groundwater model was created to evaluate the potential for the radioactivity in the residues to leach to onsite groundwater and then also evaluate whether or not any radioactivity would ever migrate off-site in the groundwater. In addit
