Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAPIn 1982 and 1983, evidence of a significant release of radioactivity was discovered at the OldHardstand. This release was apparently associated with outdoor storage of contaminatedequipment and radioactive waste by NFS. Leakage from that equipment contaminated thehardstand’s asphalt surface and the adjacent soil and drainage ditch. Gamma radiation levels ashigh as 1,500 mR/hr were measured two inches above the ground surface. In 1983, abovegroundportions of contaminated trees were removed. In 1984, approximately 1,700 cubic yards ofmaterials (asphalt, soil, and vegetation) were removed from the area and placed in thedecommissioned Lagoon 1. (Waste from Lagoon 1 had previously been transferred to Lagoon 2;both lagoons are in WMA 2.) Lagoon 1 was then capped with a clay cover. In 1991/1992, somelow levels of radioactively contaminated soil were encountered along the northeastern margin ofthe Old Hardstand; soils above background levels were placed in storage containers and taken toon-site storage facilities. A 1995 estimate of the activity in the debris placed in Lagoon 1 totaledapproximately 18 Ci (DOE 2004 Section 4.6.1, DOE 2009 Table 2-17; DOE 2010Section 3.11.5). This release likely has contributed to the North Plateau Groundwater Plume.E.4.3.2Waste Tank Farm Valve Pit SpillPotentially Affected Media:Potentially Affected WMAs:surface soil, subsurface soil, groundwater1, 2, 3, 4, 5, 6 (North Plateau Groundwater Plume)In 1985, a spill of radioactive water occurred in a valve pit located in WMA 3, northwest of Tank8D-2. A condensate line failed at its flanged valve bolts. Approximately 500 gallons werereleased at 4.6 E-02 uCi/mL gross beta and 4E-03 uCi/mL tritium. Some condensate flowed outof the valve pit into the drainage ditch extending towards the Old Hardstand in WMA 5 and/ortowards WMA 2. The radioactive condensate reached the point in the drainage ditch where theditch turns to the northeast, near the corner of the New/Old Hardstand. At this point, the ditch wasblocked to prevent further downstream flow. The release primarily impacted surface soil in WMA3. Contaminated soil was removed (DOE 2009 Table 2-18; DOE 2010 Section 3.11.5). Thisrelease likely has contributed to the North Plateau Groundwater Plume.E.4.3.3Spent Resin Drum SpillPotentially Affected Media: subsurface soil, groundwaterPotentially Affected WMAs: 5Rev. 1 E-7