U.S. Army Corps of Engineers and U.S. Department of Energy partnering for cleanup of the 1100 Area, Hanford Site, Washington

The US Department of Energy's Hanford Site was listed on the National Priorities List (NPL) in July 1989 and was divided and listed as four Sites: the 1100 Area, the 100 Area, the 200 Area, and the 300 Area. Each Area was further divided into sub-units called Operable Units. This paper describes Remedial Investigation and Feasibility Study activities for the 1100 Area leading to the first Record of Decision at the Hanford Site. Key issues included: (1) Definition of future land use; risk assessments and resulting remedial actions depended heavily upon future land use definition because no significant exposure pathways currently exist for the Site, (2) Potential impacts of groundwater contamination to a nearby groundwater well field supplying potable water to Richland, (3) Coordination with an offsite potentially responsible party (PRP) from whose property the groundwater contamination emanated, and (4) The development and determination of precedent setting cleanup requirements and approaches for the entire Hanford Site. The US Army Corps of Engineers, Walla Walla District, performed work leading to the signing of the Record of Decision in September, 1993. The Corps continues to perform investigative, design, and remedial action work at areas of the Site including activities supporting the cleanup and ultimate release of two large portions of the Hanford Site known as the Arid Lands Ecology Reserve (ALE) and the North Slope. These two areas comprise more than half of the total area of the entire Hanford reservation