Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAPand sediments, and based on a combination of historical data and more recent sampling results forsubsurface soils. As part of the analysis, average and maximum results were presented.For CSAP pre-remediation decision-making, background comparisons will be based on resultsfrom the reference area surface soil sampling. The 95% UTL will be estimated for eachradionuclide that could be expected to be present in measurable quantities in background soils(i.e., naturally occurring radionuclides and those anthropogenic radionuclides present inbackground surface soils due to historical fallout) based on the 0- to 15-cm-deep sample resultsand the 15-cm to 1-m-deep sample results. The raw sample results will be used to perform thiscalculation regardless of whether sample results are considered detections or not.Background comparisons will be based on depth (i.e., 15-cm to 1-m-deep samples to 15-cm to 1-m-deep reference area sample results, 15 cm deep samples to 15 cm deep reference area sampleresults). For surface soils, a sample result will be considered inconsistent with background if theactivity concentration of one or more radionuclides exceeds its respective 95% UTL. Forsubsurface soils, the point of comparison will be to 15 cm to 1 m deep reference area sampleresults. The same rule for surface soils will apply for those radionuclides that are naturallyoccurring. In the case of the Pu-239, measurement error is expected to be significant with respectto measurable background activity concentrations. If the application of the rule described aboveresults in an unacceptably high rate of false positive “hits” for Pu-239, the comparison processmay be modified with NYSERDA concurrence to also account for measurement uncertainty.For those radionuclides that are anthropogenic and site-related, a surface or subsurface soilsample result greater than three times its reported uncertainty will be considered inconsistent withbackground conditions.For samples that fail either the 95% UTL or the three-times-uncertainty rule (whichever isapplicable), re-analyses may take place to verify that the observed result is not a product ofanalytical error alone.Sediment sample results will be compared to 15 cm deep surface soil sample results, using thesame protocol as described above for surface soils.Rev. 1 63