The Hanford 100-Area sits along the Columbia River in Benton County, Washington, covering 26 square miles. It housed nine plutonium production reactors built between 1943 and 1963, all of which have shut down. Decades of reactor operations discharged contaminated cooling water into the river and underground disposal areas, buried solid radioactive waste on-site, and left more than 400 waste disposal locations. The site was added to the National Priorities List in October 1989, and active cleanup has been underway since the mid-1990s.
Contaminants affect both soil and groundwater across the site. Chemical contaminants include heavy metals such as arsenic, cadmium, chromium, lead, and mercury, along with polychlorinated biphenyls, petroleum hydrocarbons, and trichloroethene. Radioactive contaminants include cesium-137, strontium-90, cobalt-60, plutonium isotopes, tritium, uranium isotopes, americium-241, and several other radionuclides. Nitrate and nitrite are also present in groundwater. Over 11 square miles of groundwater have been affected.
The U.S. Department of Energy owns and operates the facility and leads cleanup. The EPA serves as the lead regulatory agency under CERCLA (the Comprehensive Environmental Response, Compensation, and Liability Act). Cleanup actions have included removing over 18 million tons of contaminated soil to a lined landfill, dismantling six reactor buildings and placing them in interim safe storage, and running pump-and-treat systems with barrier walls to reduce contaminant seepage toward the Columbia River. The B Reactor is now part of the Manhattan Project National Historical Park. Radioactive concentrations detected in the river remain within EPA and Washington State drinking water standards.
Institutional controls restrict access to contaminated soil and groundwater, meaning there are no present risks to people from direct exposure. However, groundwater migration is not yet under control and remedy construction has not been completed across the entire site. Several operable units are still in active remedial action, investigation, or feasibility study phases, with some estimated completions in late 2026. The most recent five-year review was completed in April 2022, and the next is estimated between May and July 2027.
Community members can stay involved by contacting the Community Involvement Coordinator or the Remedial Project Manager. Public records are available through the EPA Superfund profile system, and a full copy of the Administrative Record can be reviewed at 2440 Stevens Center Place, Room 1101, in Richland, Washington. Additional site information is available at http://pdw.hanford.gov/arpir/.
