Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAP1998, or 2008, and most targeted the North Plateau Groundwater Plume source areaadjacent to and beneath the Process Building. The exception is location SNLAUB1, a soilsample collected in 2004 from an unreported depth just east of the utility room and northof the utility room expansion. Table A.1 summarizes which radionuclides have data forWMA 1.Each core from WMA 1 had at least one subsurface soil sample analyzed for Sr-90 andyielded at least one detectable Sr-90 result. The results ranged from approximately 0.1pCi/g along the southern boundary of WMA 1 (BH-20) to more than 9,000 pCi/g (GP-7608) directly beneath the center of the Process Building. Figure A.15 shows a profileview for some of these cores with their Sr-90 results.• There is a significant amount of groundwater data for WMA 1 available within ELIMSfrom historical characterization work addressing the North Plateau Groundwater Plume.These data were obtained from monitoring wells and from groundwater samples obtainedby GeoProbe. Figures A.16 and A.17 show the locations of groundwater data collectioncolor-coded by Sr-90 and tritium results, respectively. The detection limits for Sr-90 andtritium varied widely among ELIMS samples. 10 pCi/L and 500 pCi/L were selected asthresholds for Sr-90 and tritium, respectively, because based on ELIMS data resultsabove these activity concentrations were consistently above method detection limits andso indicative of contamination impacts rather than simply measurement error.Contamination was encountered throughout WMA 1 and was dominated by Sr-90, withhighest concentrations immediately down gradient of the presumed 1968 release point,and lowest concentrations along the southern boundary of WMA 1.A.6 Planned Phase 1 DP ActivitiesFor a more complete description of planned Phase 1 DP activities, see the Phase 1 DP, Section3.1 and Section 7.3.All buildings within WMA 1 are slated for demolition and removal as part of Phase 1 activities aswell as the three underground waste water tanks and the underground lines that fall within theexcavation footprint.Rev. 1 A-10