Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAPHowever, this is not the case with Sr-90. DOE is currently exploring prototype systems based ongas proportional counting detectors that may prove to be valuable for real-time screening ofexposed excavation soil surfaces for Sr-90. However, this plan assumes that in areas where eitherpre-excavation CSAP data collection or historical data sets identified Sr-90 impacts, soilsampling and analysis will be required as part of remedial action survey activities. Theexpectation for both Cs-137 and Sr-90 is that rapid turn-around analytical support will beavailable as part of remedial action survey activities, and that those methods (gammaspectroscopy for Cs-137 and liquid scintillation for Sr-90) will have sufficiently low detectionlimits to support the required decision-making at CG w activity concentrations.If pre-excavation CSAP data results determine that there are other radionuclides that are alsopotential risk drivers in addition to Cs-137 and Sr-90, the remedial action survey approachesdescribed here will be modified to address those radionuclides as well.The following sections describe remedial action survey data collection in support of specificPhase 1 activities.7.1 WMA 1 and WMA 2 Excavation SupportIn both the WMA 1 and WMA 2 excavations, initial excavation footprints will have been definedon the basis of CSAP data results and the physical requirements associated with subsurfacebuilding/lagoon infrastructure removal. The presence of slurry or sheet pile walls on all four sidesof the WMA 1 excavation and along the north, west, and east sides of the WMA 2 excavation willlimit the extent the excavations can extend laterally in response to encountering unexpectedsubsurface contamination in excavation side walls as the excavations proceed. The depth of boththe WMA 1 and WMA 2 excavations will extend a minimum of 1 ft into the Lavery Till.In the case of WMA 1, along the north, west, and south sides of the excavation, the soil surfacewill be sloped from the floor of the excavation up to land surface at an angle of approximately 45degrees. Along these sides at the land surface, the top of the excavation will be extended up to thesheet pile wall installed for water control. Along the east side of the excavation, the excavationfloor will be extended to the slurry wall.Rev. 1 54