Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAP• A minimum of four samples from each core will be submitted: one representing the top 1m of soil, one representing the top 1 m of Lavery Till, one representing the 1-m soilinterval immediately on top of the Lavery Till, and one representing the 1-m intervalstraddling the water table. In addition, if the down-hole or ex situ scan identifies elevatedreadings and the highest readings do not correspond to one of these four intervals, the 1-m interval representative of the highest gross activity readings will be submitted foranalysis. Since the depth to the Lavery Till varies significantly, the total depths of the soilcores will also vary significantly depending on where they are collected. If the depth totill is less than 3 m, the minimum number of samples will be adjusted accordingly. In thecase of slurry wall core locations, only two samples will be collected, one representingthe top 1 m of Lavery Till and one representing the 1-m soil interval immediately on topof the Lavery Till.The reason for collecting a sample from the top 1 m of soil is to define the extent ofsurface soil contamination. The objective of the Lavery Till sample is to understand thecontamination status of the underlying Lavery Till. The purpose of the soil samplesimmediately above the Lavery Till is to determine the presence/absence of contaminationimmediately above the Lavery Till and to have a point of comparison for Lavery Tillsample results. The rationale for the sample from the interval straddling the water table isbecause contamination migration is likely via contaminated groundwater and releasesabove the water table. Consequently, in the vicinity of releases, a likely zone to encountercontamination is in soils along the water table. The reason for the biased sample is tounderstand the maximum levels of contamination that are present if the depth of thatcontamination does not correspond to one of the other depth intervals already sampled.• Three groundwater samples will be collected from each subsurface sample location ifpossible: one from the water table, one from immediately above the Lavery Till, and onemidway between these two intervals. In general, away from source areas, activityconcentrations for affected groundwater, as measured in picocuries per liter, would besignificantly greater than activity concentrations in impacted soils at the same location, asmeasured in picocuries per gram. Consequently, groundwater activity concentrationsserve as a conservative indication of the potential for subsurface soil contamination.These data will also provide insights into the extent of subsurface groundwatercontamination.Rev. 1 42