Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAP• Subsurface releases from the Process Building have impacted subsurface soils andgroundwater in WMA 6 along the WMA 1 boundary. The lateral extent of these impactsis currently unknown.• GPBG0408, a “background” soil bore completed adjacent to the WMA 6 boundarywithin WMA 10 just south of the New Warehouse and the Sewage Treatment Plantencountered tritium soil contamination at a depth of approximately five feet. While theexact source is unknown and tritium was the only radionuclide above background, it doesraise potential subsurface concerns for this area, assuming that the original release pointwas within WMA 6 and not WMA 10. The cluster of wells directly south of the SewageTreatment Plant showed some indications of elevated gross beta and tritium activityabove background levels in the 1990s. The soils and groundwater data suggest that thereis the potential for very low level impacts of soils/groundwater in this vicinity.• Sediments within the Demineralizer Sludge Ponds are known to be contaminated,although the depth of contamination is not known.• There is evidence of low levels of contamination in the sediments for the ditch thatcurrently drains WMA 10 in a southeasterly fashion along the Rail Spur beforeconnecting with Erdman Brook.Because the Old Warehouse pre-dates the 1968 airborne releases of radioactivity from theProcess Building stack, the assumption is that soils beneath the Old Warehouse slab are unimpacted.Figure F.15 shows the current Conceptual Site Model (CSM) for WMA 6 surface soils. FigureF.16 shows the same for soils deeper than 1 m. Particularly for subsurface soils, the CSM is basedon very little data and is primarily conjecture at this stage. Figures F.15 and F.16 also show thefootprints of the planned deep excavations for WMA 1 and WMA 2. Note that the plannedexcavations for WMA 1 and WMA 2 extend into portions of the northern part of WMA 6.F.8 WMA 6-Specific Characterization Goals• Evaluate Appropriateness of the Current List of Radionuclides of Interest (ROI)Rev. 1 F-11