Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAP• In 1990 and 1991 a second static direct exposure measurement program was conducted(WVNSCO 1992). In the case of WMA 2, this effort provided systematic coverage for allof the WMA 2 area on a 10-m grid. This data collection used different instrumentationand protocols than the 1982 study, so the results are not quantitatively comparable.Figure B.13 shows these results. These data also indicated potentially significant surfacecontamination within the WMA 2 boundary, with the same general pattern of fallingactivity levels as one moves from west to east; interpretation of these data is complicatedby the possibility of shine effects from the Process Building and other facilities. Inaddition, the 1990/1991 survey identified more localized elevated areas immediatelyadjacent to Lagoons 2, 3, 4, and 5.• There are some soil sampling data for WMA 2 available within ELIMS. Figure B.14shows the locations of surface soil samples, sediment samples and soil cores withsubsurface soil samples. The bulk of the data was either collected as part of the 1993 sitewidecharacterization effort, or as part of the 2008 North Plateau Groundwater Plumecharacterization work. The exception is NP5, which was completed in 1994. Table B.1summarizes which radionuclides have data for WMA 2. Figure B.14 also shows surfacesoil Cs-137 and Sr-90 activity concentrations where those were available.There are very limited surface soil data available within ELIMS. In general these datashow higher activity concentrations in the western portion of WMA 2 and lower activityconcentrations to the east, as one would expect. Subsurface data identified elevatedactivity concentrations throughout WMA 2 to depth. The mix of radionuclides presentand the depth where maximum concentrations are encountered varies depending onlocation. For contamination associated with the North Plateau Groundwater Plumeoriginating from a subsurface release beneath the Process Building, Sr-90 is the onlyradionuclide significantly elevated above background levels in soils. For contaminationassociated with discrete releases within WMA 2, such as leaching from Lagoon 1 orreleases in the western portion of the site, Cs-137 often dominates. Figure B.18 providesa cross-sectional view that includes several soil core locations along with their samplingresults in the lagoon area of WMA 2.Rev. 1 B-15