Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAPB.4.3.1Wastewater Treatment OperationsPotentially Affected Media:Potentially Affected WMAs:surface soil, subsurface soil, groundwater, sediments1, 2, 3, 4, 5, 6 (North Plateau Groundwater Plume),12 South (Erdman Brook)All operational units used to treat radioactive wastewater are expected to contain residualradioactivity. These operational units are: the Low-Level Wastewater Building, the Lagoons(particularly Lagoons 1 and 2, and primarily in the sediment), the French Drain, theNeutralization Pit, the Old Interceptor, the New Interceptors, and all associated undergroundpipelines.Further, the design of some of these units allowed contaminated water to infiltrate groundwaterand/or surface water (Erdman Brook) as part of standard operation:• Lagoon 1 allowed liquid to seep from the lagoon into the surrounding sand/gravel layer,while retaining sediment. Specifically, tritiated water (originally containing about 6,000curies of tritium in leachate pumped from the SDA (WMA 8) for treatment) was allowed toseep from Lagoon 1 and infiltrate areas of the North Plateau groundwater during the mid-1970s. These conditions resulted in an extensive investigation by NFS, extending through thetransfer of operational control to DOE in 1982. Consequently, Lagoon 1 was closed in 1984(DOE 2010 Section 3.11.5).• Similarly, Lagoons 2 and 3 historically may have discharged to groundwater. Currently, theselagoons are operated such that their water levels are maintained below the interface betweenthe sand and gravel layer and the Lavery Till. As such, they should not contributecontaminated water to groundwater in the sand and gravel layer, though they may contributesmall amounts of water to the Lavery Till. They likely act as local drains for groundwater inthe sand and gravel. Historically, however, the water levels could have been elevated, andwould have allowed discharge of contaminated water to the sand and gravel layer. Whilecontamination levels in the discharged water would have been relatively low, soil sorptionwould likely have led to an accumulation of contamination in subsurface soils adjacent tothese lagoons.Rev. 1 B-10