Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAPG.4.3 Drainage Area ReleasesPotentially Affected Media: surface soil, subsurface soil, sediment, groundwaterPotentially Affected WMAs: 7, 8A drainage area located between the SDA and the NDA is believed to contain contaminated soil.Presumably, this swale has been contaminated from spills during waste burial operations by NFS,and also during leachate control activities after SDA closure.During the NDA tank removal and subsurface control period in the 1980s and 1990s, the swalearea was re-contoured to prevent erosion. An unknown amount of low-level radioactivecontamination remains in that area, evidenced by continuing elevated radioactive contaminantindicators in surface water immediately downstream. The swale area is approximately 30 feetwide and runs approximately 300 feet north, along the drainage from the NDA Hardstand. Basedupon observations during radiation surveys in 1982, the contamination appeared to havepermeated porous fill in the swale channel. Gamma readings in that area were five to seven timesbackground, not inconsistent with observed downstream gross beta contamination. Surface soilcontamination is still occasionally noted in that area.G.5 Existing DataExisting data sets for this area include:• Extensive historical record searches and modeling have been used to determine theactivity contents of the NDA (WVNSCO 1982).• In 1982 static direct exposure readings were collected across the WVDP premises(WVNSCO 1992). Only a small portion of WMA 7 was covered by these measurementson a 10-m grid. Figure G.12 shows these results color-coded by the exposure readingsencountered, with the data overlain on a 1977 aerial photograph. The data indicateelevated surface contamination associated with the two WMA 7 drainage features.Rev. 1 G-8