Rocky Flats Plant sits on 6,240 acres northwest of Denver and operated as a nuclear weapons manufacturing facility from 1952 to 1989. Manufacturing activity, fires, spills, and poor waste management contaminated soil, sediment, groundwater, and surface water across the site. The most severe contamination was concentrated in the 385-acre industrial core, where nearly 800 buildings once stood. The site was added to the National Priorities List (NPL) in 1989, making it eligible for federal Superfund cleanup funding and oversight.
Ten contaminants of concern drive cleanup decisions at the site. Radioactive materials include plutonium-239, plutonium-240, and americium-241. Chemical contaminants include arsenic, benzo[a]pyrene, a dioxin compound known as TCDD, and vanadium. Most contaminants are found in soil. Plutonium-239 and plutonium-240 also appear in offsite sediment.
Cleanup ran from 1990 to 2006. Workers demolished more than 800 buildings and removed more than 500,000 cubic meters of low-level radioactive waste. Some contamination remained in core production areas, settling ponds, and two landfills within the industrial zone, but studies concluded that remaining contamination poses no threat to human health or the environment at current levels. In 2007, the surrounding buffer zone became the Rocky Flats National Wildlife Refuge. That land was never used for production and sampling confirmed it is safe for public use. The Department of Energy manages ongoing monitoring, with EPA and the Colorado Department of Public Health and Environment (CDPHE) providing oversight.
The site is not yet fully ready for anticipated reuse. Two key performance measures remain unresolved. Human exposure control cannot be confirmed because of uncertainty about whether current exposures are safe. Groundwater migration control cannot be confirmed because of uncertainty about whether contaminated groundwater is stabilized. The most recent five-year review was completed in July 2022, and the next is estimated for between August and October 2027. Full sitewide readiness for anticipated reuse is estimated between September and November 2028.
Community members can get involved by contacting EPA's Community Involvement Coordinator. Technical cleanup questions can go to the EPA Remedial Project Manager. CDPHE also has contacts for state-level program and community questions. Site documents, including the Fifth Five-Year Review completed in May 2022, are available at the EPA Superfund Records Center in Denver at 1595 Wynkoop Street, or through CDPHE's Hazardous Waste Management Division Records Center.
