Rocky Flats, Colorado, was a nuclear weapons plant about 16 miles northwest of Denver that manufactured plutonium triggers for American warheads from 1952 until an FBI raid shut it down in 1989. After roughly $10 billion in cleanup work, the site was split in two: a fenced-off core still controlled by the Department of Energy, and a surrounding buffer zone that reopened to the public in 2018 as the Rocky Flats National Wildlife Refuge. Whether that land is truly safe for hikers, cyclists, and the growing suburbs nearby remains one of the most contested environmental questions in the American West.
What the Plant Made
The Atomic Energy Commission picked the Rocky Flats site in 1951, and production started the next year. For nearly four decades the plant specialized in plutonium pits, the fission cores that trigger thermonuclear weapons. At peak Cold War output, Rocky Flats turned out between 1,000 and 2,000 pits a year and was the only facility of its kind in the country.1Department of Energy. Enhanced Website Brings to Life the Story of the Rocky Flats Site in Colorado
The work involved plutonium metallurgy along with beryllium, stainless steel, and a long list of hazardous chemicals. Thousands of technicians and engineers worked inside a tightly guarded perimeter, and the facility eventually grew to more than 800 structures spread across 6,240 acres.2US EPA. Rocky Flats Plant (USDOE) Dow Chemical ran the plant for the government until 1975, when Rockwell International took over the operating contract.3U.S. Department of Energy Office of Legacy Management. Rocky Flats Site History
Fires and Off-Site Contamination
Two fires shaped how people around Denver came to see Rocky Flats. The first, in September 1957, broke out inside a plutonium fabrication building and breached the air filtration system. A study sponsored by the Colorado Department of Public Health and Environment later estimated the highest off-site dose from the release at roughly 13 microsieverts.4PubMed. Plutonium Releases from the 1957 Fire at Rocky Flats
The second fire, on May 11, 1969, was worse. A plutonium briquette self-ignited inside a glovebox in Building 776, and the fire spread into connected Building 777 within 25 minutes. Thirty-three firefighters fought the blaze for nearly six hours, pumping 41,000 gallons of water per hour. The two buildings held a combined 3,400 kilograms of plutonium. The amount actually released off-site was far smaller, estimated at 140 to 900 milligrams, but property damage reached about $26 million in 1969 dollars, roughly $200 million in today’s money.5Department of Energy. The 1969 Rocky Flats Fire – We Should Not Forget
The 903 Pad
The slower problem turned out to matter more. During the 1950s and 1960s, more than 3,500 fifty-five-gallon drums of waste oil contaminated with plutonium sat outdoors in an area the plant called the 903 Pad. The drums corroded. Oil leaked into the soil. Wind then carried contaminated soil off the plant and into the surrounding area.6Department of Energy. Rocky Flats History A later study estimated the total plutonium released beyond plant boundaries from the 903 Pad at about 0.26 TBq, with the highest predicted off-site dose around 72 microsieverts.7PubMed. Plutonium Release from the 903 Pad at Rocky Flats Workers paved the pad with asphalt in 1969, but elevated plutonium levels kept turning up in topsoil southeast of the pad into the mid-1970s, and that discovery drove much of the community anger that would later focus federal attention on the plant.
The 1989 FBI Raid
On the morning of June 6, 1989, more than seventy-five FBI and EPA investigators arrived at the Rocky Flats gates with a search warrant. They were looking at suspected criminal violations of environmental law, including the illegal burning of plutonium-contaminated waste in Building 771’s incinerator and unauthorized discharges of radioactive liquid into local waterways. It was the first time in American history that two federal agencies raided another federal agency.
A grand jury investigation ran from mid-1989 to mid-1991. Jurors heard from 110 witnesses and reviewed more than 2,000 exhibits. In 1992, Rockwell International pleaded guilty to ten environmental criminal charges, five felonies and five misdemeanors, covering illegal storage and treatment of hazardous waste, contaminated discharges, and other violations of the Resource Conservation and Recovery Act and the Clean Water Act. The company paid an $18.5 million fine, a record environmental penalty at the time.8FindLaw. United States v Rockwell International Corporation Plutonium pit production never resumed. The site’s mission shifted from manufacturing to tearing itself down.
Cleanup
Rocky Flats was designated a Superfund site, and remediation ran from roughly 1990 through late 2005 under EPA and Colorado Department of Public Health and Environment oversight. Workers demolished and removed more than 800 buildings and shipped over 500,000 cubic meters of low-level radioactive waste off-site.2US EPA. Rocky Flats Plant (USDOE) In 2006, the EPA determined that no further cleanup was needed.
The price depends on what you count. The DOE has cited roughly $7 billion for the core cleanup contract completed in December 2005.1Department of Energy. Enhanced Website Brings to Life the Story of the Rocky Flats Site in Colorado A Government Accountability Office review put the full cost at about $10 billion in constant 2005 dollars once contractor fees, the DOE field office, pension and benefits liabilities estimated at $1 billion over sixty years, and projected long-term stewardship through 2080 are added in.9U.S. Government Accountability Office. Nuclear Cleanup of Rocky Flats – DOE Can Use Lessons Learned to Improve Oversight of Other Sites Cleanup Activities
Two Zones, Two Rules
The land was divided for management. The Central Operable Unit, the former industrial core, remains under DOE control and is closed to the public. The restrictions on it are strict: no occupied buildings, no groundwater wells except for cleanup purposes, no digging below three feet without regulatory approval, and no use of surface water for drinking or agriculture.10U.S. Department of Energy Office of Legacy Management. Rocky Flats Site Operations Guide Underground remnants of buildings, process waste lines, and burial pits are still in the subsurface beneath this restricted area.
The Peripheral Operable Unit, the outer buffer zone, is what became the wildlife refuge. Testing by regulators found that contamination there met federal and state thresholds for public use.
Can You Visit Rocky Flats Today?
Yes, the buffer zone. The Rocky Flats National Wildlife Refuge Act of 2001 directed transfer of the buffer lands to the Interior Department once EPA signed the final cleanup decision, and set the refuge up to restore native ecosystems and provide compatible public recreation.11Congress.gov. S 425 – Rocky Flats National Wildlife Refuge Act of 2001 The U.S. Fish and Wildlife Service now manages the refuge, which offers about 15 miles of moderate trails through mixed-grass and tallgrass prairie. The trails are open year-round for hiking, wildlife viewing, photography, bicycling and Class 1 e-bikes, cross-country skiing, snowshoeing, and horseback riding.12U.S. Fish & Wildlife Service. Rocky Flats National Wildlife Refuge – Visit Us Elk, deer, and birds of prey use the landscape.
Visitors are confined to designated trails. All other refuge lands and staff roads are off-limits. Off-trail hiking or biking, removing natural or cultural objects, camping, building structures, littering, and driving motorized vehicles off designated roads are all prohibited.13U.S. Fish & Wildlife Service. Rocky Flats National Wildlife Refuge Rules and Policies The rules protect wildlife and also minimize soil disturbance in an area with a radioactive history.
Is It Safe? The Dispute
The refuge opened on September 15, 2018, over organized opposition. Environmental groups argued that foot traffic and cycling would stir up residual plutonium particles in the soil. A coalition led by the Rocky Mountain Peace and Justice Center filed suit to block the opening, though a judge declined to issue an injunction. Several school districts, including Boulder Valley, Denver, and Jefferson County, banned teachers from taking students to Rocky Flats on field trips.
The litigation has continued. In 2024, Physicians for Social Responsibility and five other Colorado advocacy groups filed a federal lawsuit arguing that agencies failed to adequately consider alternatives to routing a trail through a portion of the refuge they consider contaminated with plutonium. The EPA and the state health department have maintained that the refuge is safe for workers and visitors based on soil and air testing. If you are deciding whether to visit, those are the two positions on the table and both are still being argued.
Compensation for Former Workers
Former Rocky Flats workers may qualify for federal compensation under the Energy Employees Occupational Illness Compensation Program. People employed at the plant from April 1, 1952, through December 31, 1983, who accumulated at least 250 work days are members of a Special Exposure Cohort, which simplifies claims for radiation-linked cancers and other covered conditions.14Office of Workers’ Compensation Programs. Rocky Flats Plant – Division of Energy Employees Occupational Illness Compensation The program is run by the Department of Labor’s Office of Workers’ Compensation Programs.
Long-Term Monitoring
The Central Operable Unit is governed by the Rocky Flats Legacy Management Agreement, a three-party enforcement agreement among the DOE, the EPA, and the Colorado Department of Public Health and Environment.15U.S. Department of Energy Office of Legacy Management. Rocky Flats Legacy Management Agreement DOE’s Office of Legacy Management runs a surveillance program that includes regular collection of air, surface water, and groundwater samples. Federal law also requires the EPA to review Superfund remedies at least every five years at any site where contamination remains above levels that would allow unlimited use.16US EPA. Superfund Five Year Reviews The most recent Rocky Flats review was transmitted in 2022.
A local oversight group, the Rocky Flats Stewardship Council, composed of elected officials and community representatives, took over from earlier advisory boards in 2006 and reviews technical reports in public.9U.S. Government Accountability Office. Nuclear Cleanup of Rocky Flats – DOE Can Use Lessons Learned to Improve Oversight of Other Sites Cleanup Activities The Central Operable Unit must also be physically inspected at least once a year for any sign that the land-use restrictions have been violated.10U.S. Department of Energy Office of Legacy Management. Rocky Flats Site Operations Guide Plutonium-239 has a half-life of about 24,000 years, so the monitoring obligations at Rocky Flats will outlast any institution currently responsible for them.