By John Abbotts, March 14, 2025
A wildlife corridor plans to connect two Superfund sites at the former Rocky Flats plutonium plant and the Rocky Mountain Arsenal that once produced chemical weapons. Locals fear residual contamination could spread.
A life-size ‘Cold War Horse’ sculpture guards the former site of the Rocky Flats plutonium production plant, with the Denver skyline in the background. The sculpture is made of steel, fiberglass, and epoxy. (sculpture and photo by Jeff Gipe)
By John Abbotts March 14, 2025In September, the city council of Westminster, Colorado voted not to fund a pedestrian bridge and underpass at the Rocky Flats site due to concerns about residual soil contamination from plutonium and other hazardous materials. In the process, the city council withdrew about $200,000 in financial support for the development of the project, known as the Rocky Mountain Greenway.
The US Fish and Wildlife Service proposed the greenway to connect wildlife refuges at the Rocky Mountain Arsenal through hiking trails via the Two Ponds refuge to Rocky Flats, with plans to eventually connect to the Rocky Mountain National Park. But the plan is controversial: Both Rocky Flats and the Arsenal are still on the US Environmental Protection Agency’s National Priorities List, identified since 1987 as “Superfund” cleanup sites that contain residual contamination.
The US Army established the Arsenal to produce chemical weapons to support World War II efforts, and in the 1990s, the federal government leased part of the Arsenal to Shell Chemical Co. to manufacture fertilizer and pesticides. In 1952, the Atomic Energy Commission began operations at Rocky Flats as a federal atomic weapons facility, producing plutonium triggers for hydrogen bombs. (A hydrogen bomb or H-bomb uses fission in the primary-uranium or plutonium-to trigger the secondary into a fusion reaction that combines two atomic nuclei to form a single heavier nucleus, releasing a much larger amount of energy.) Operations started largely in secret at Rocky Flats, located in a sparsely populated area 16 miles upwind and upslope of the city of Denver. But in the late 1970s, the public became more informed about plant operations, and the movement opposing atomic weapons began to focus on the facility, organizing protests and civil disobedience actions.
Rocky Flats Plant plutonium buildings (“700” area) in 1988. Building 707 (L-shape building in top right corner) was the plant’s main plutonium manufacturing and assembly facility. National Park Service
Rocky Flats workers inspect plutonium storage vault in building 707. They use the automated X-Y retriever to sort and retrieve plutonium metal from the storage vault for distribution to other processes in the building. Energy Department
Rocky Mountain Arsenal south plant, circa 1970. The plant produced both conventional and chemical munitions, including white phosphorus, napalm, mustard gas, and chlorine gas. Later, the Army leased the Arsenal facilities to private industries to manufacture fertilizer and pesticides. National Park Service
By the late 1980s, when the federal cleanup program at both sites had been initiated, work had already begun on the new Denver International Airport on Rocky Mountain Arsenal lands, and the Denver suburbs had steadily spread west toward Rocky Flats. Accordingly, there was consensus at each site that expedited cleanup would most effectively protect the metropolitan area, and cleanup standards were looser than “unrestricted use” to develop national wildlife refuges at each site. The consequences were residual contamination, especially at Rocky Flats, where there was no limit on how much plutonium remained below six feet of soil in an industrial area fenced off from the public and with the surrounding land converted to a wildlife refuge. This “cleanup on the cheap” at Rocky Flats, plus a record of cover-ups of accidents at the site, created continuing distrust and controversy over post-remediation uses near Rocky Flats. Cities and citizens opposed different proposals for re-use, even over the issue of public access to the refuge. Now there are concerns that the proposed greenway-a trail between the two tracts-may facilitate cross-contamination, taking radioactive material from the Rocky Flats site to the chemically hazardous Arsenal property, and vice versa.
Conceptual map for Rocky Mountain Greenway, Colorado. Jefferson County Colorado
Each of the two Rocky Mountain sites has a controversial history. At Rocky Mountain Arsenal, chemical contaminants have been identified as organochlorine pesticides, akin to DDT and its chemical cousins, of which Rachel Carson warned in her classic 1962 book Silent Spring. Other contaminants at the site include heavy metals, organophosphate, and carbamate pesticides-with each of these pesticide classes known to be neurotoxic-along with a potpourri of other chemical contaminants in groundwater.
As for Rocky Flats, a 1972 paper from radiochemist Edward Martell and one of his colleagues at the National Center for Atmospheric Research in Boulder, Colorado reported that just east of the site boundary levels of radioactive plutonium 239 and americium 241 ranged “up to hundreds of times that from nuclear tests.” In 1969, a highly visible fire at the site’s plutonium processing facility sparked off-site monitoring; at the time, the fire was assumed to be the source of the detected contamination. Later, the Atomic Energy Commission was forced to admit that a 1957 fire in a separate plutonium recovery building or leaks from drums containing plutonium-contaminated waste were more likely the source of off-site soil contamination.
A waste storage barrel, tipped on its side shows corrosion and leackage on pad 903. The pad was the main source of plutonium and americium contamination at the Rocky Flats Plant site. Energy Department
Waste drums containing plutonium-contaminated solvents and oils are stored outside on bare ground at the pad 903 in 1962. In total, over 8,000 waste drums were stored throughout all buildings at Rocky Flats, including 4,000 on this pad alone. The drums were removed in 1967 and 1968. Energy Department
Workers proceed to soil sampling at pad 903 circa 2005 after the waste drums were removed and an asphalt pad was installed to control the spread of contamination. Energy Department
When the Rocky Flats facility was still operating, it accepted contaminated metal from another Atomic Energy Commission facility. In the process of treating and burying the waste, Rocky Flats released tritium into a nearby stream, contaminating the drinking water source for the city and county of Broomfield, five miles west of the facility. The contamination occurred for more than a decade leading up to 1970; the tritium remained undetected until 1973.
In 1986, amendments to Superfund legislation expanded the authority of the Environmental Protection Agency (EPA) to oversee the cleanup of contaminated federal facilities. The following year, the agency designated Rocky Mountain Arsenal as a Superfund site.
Then, in June 1989, the FBI and EPA raided the Rocky Flats plant in response to allegations of multiple environmental crimes at the site. After an investigation, plutonium production ended, the EPA designated Rocky Flats a Superfund site in the same year. In 1992, Rockwell International, the contractor in charge of managing the site, pleaded guilty to environmental crimes and paid a fine of $18.5 million.
The regulatory agencies responsible for environmental cleanup-the EPA’s Region 8 office, based in Denver, and the Colorado Department of Public Health and Environment-have certified cleanup as partially complete at each site. The “responsible parties” are now the US Army for the Arsenal and the US Department of Energy for Rocky Flats.
At the Rocky Mountain Arsenal, cleanup extended to 10 feet below the surface, considered a sufficient depth to prevent burrowing animals from spreading the widespread chemical contamination there. In 2010, the regulatory agencies determined parts of the Arsenal sufficiently remediated to serve as a National Wildlife Refuge and transferred the management of the designated property to the US Fish and Wildlife Service. That service transferred a small herd of bison from a national range in Montana, and bison continue to inhabit the refuge.
The Army retains responsibility for a central area, along with smaller contaminated locations covered for monitoring and groundwater remediation. In 2019, the Colorado Department of Public Health sued Shell and the Army in the US District Court for hazardous chemicals from the Arsenal leaking into groundwater. The suit alleged that unsafe levels of organochlorine pesticides, heavy metals, chlorinated and aromatic solvents, and chemical agent degradation products and manufacturing byproducts had been found in groundwater. Litigation on that case is still ongoing.
At Rocky Flats, the controversy over the site’s past activities extended into its cleanup, with some opponents characterizing the proposed plans as “bait-and-switch.” Early in the cleanup process, the Energy Department funded an advisory committee that, in turn, established a “future site uses” working group. One of the working group’s recommendations was for residual plutonium contamination to be cleaned down to background level, to protect future area residents, no matter how long it would take. However, state officials assessed that a speedy cleanup that converted some areas into a National Wildlife Refuge was the desirable approach to protect outer metropolitan areas expanding toward the site boundaries.
Rocky Flats workers bag and repackage residues in 2002. Energy Department
Repackaged waste drums at Rocky Flats awaiting transfer to another site of the Energy Department’s nuclear weapons complex. US Government
Workers use the “Sludge Daddy” to remove the final 95,000 gallons of sludge from a Rocky Flats building in February 2004. Energy Department
The Energy Department and the site’s federal and state regulators agreed to limit the total costs of remediation and established a residual plutonium contamination limit in the top three feet of soil and a higher limit between three and six feet. (There was no contamination limit below six feet.) These limits were sufficient to qualify outer areas of Rocky Flats as a National Wildlife Refuge, and those areas were released to the Fish and Wildlife Service in 2006. Since then, the controversy has remained because the residual contamination is too high for unlimited uses of Rocky Flats.
The city of Westminster is now the third municipal government to express concern over residual contamination at Rocky Flats. In 2016, the town of Superior, north of the site, voted to withdraw from the Rocky Mountain Greenway, a Federal Lands Access Program grant and project. The city and county of Broomfield followed suit in October 2020, unanimously approving a resolution for the withdrawal from the greenway. The Broomfield city council hired an environmental consultant to conduct soil sampling along the proposed Greenway, and the resolution expressed concern over the high levels of plutonium detected in the soil. After the resolution, the city stated that it would not contribute the $105,000 that was supposed to go to the Greenway project and would not allow Greenway-related construction work on Broomfield property.
The city of Broomfield also opposed another post-cleanup proposal-the Jefferson Parkway Highway Authority-described on its web page as a “privately-funded, publicly-owned regional toll road.” The proposed road would pass just outside the wildlife refuge, which was the eastern boundary of the former plutonium facility. The parkway authority had no plans to sample soil nearby until both Broomfield and a citizens advisory board recommended doing so before construction began. The authority then started sampling and, in September 2019, reported a sample containing 264 picocuries of plutonium per gram. (A picocurie is one trillionth of a curie, a measure of radioactivity.) This was much higher than the maximum limit of 50 picocuries per gram for surface contamination within the former industrial zone. Although this was the only sample above the limit, given the authority’s earlier resistance to sampling, the community lost faith in the project’s safety.
The Broomfield city council voted unanimously in February 2020 to withdraw from the Jefferson Parkway Association, removing a $70,000 annual payment in the process. In 2022, the county of Jefferson and city of Arvada sued Broomfield in response, claiming the parkway could not continue without that county’s continued participation. But a Colorado District Court judge dismissed that suit in December 2023, urging the parties to negotiate over Broomfield’s participation. The city and county of Broomfield expressed satisfaction with that decision, and the parkway’s future was described as “uncertain.”
Wildlife refuges of Rocky Flats (west, public access area in dark blue) and Rocky Mountain Arsenal (east). The Two Ponds national wildlife refuge is small and unlabeled, to the west of Westminster. Denver International Airport lies east of the Rocky Mountain Arsenal refuge, and populated areas border each of the three refuges. Remaining partners for the Rocky Mountain Greenway are the counties of Jefferson and Boulder, and the cities of Boulder and Arvada. US Fish & Wildlife Service
In an escalatory move, in January 2024, the Colorado state chapter of the Physicians for Social Responsibility and five other groups filed a federal lawsuit in Washington D.C., seeking to prevent the greenway from coming through Rocky Flats. The plaintiffs sought to enjoin the US Federal Highway Administration, US Fish and Wildlife Service, and their respective cabinet departments (Transportation and Interior), from constructing an eight-mile trail through the most heavily plutonium-contaminated area of the wildlife refuge. (The filing assumed that the greenway would proceed from Westminster, but that city’s most recent decision to withdraw funds seems to require a different route.) According to the complaint, the city of Boulder has suggested since at least 2016 that the greenway path avoid Rocky Flats entirely.
The presiding judge, Timothy J. Kelley, denied the plaintiffs’ motion for a preliminary injunction in September 2024. The case now awaits trial.
So far, concerns over Rocky Flats and its wildlife refuge have already limited public access to the refuge. Since April 2018, the Denver School District, the largest in the area, has forbidden its nearly 100,000 students from visiting Rocky Flats on field trips. Other school districts, including Boulder’s, had previously issued similar orders to protect their students.
Rocky Flats wildlife refuge in 2011 after the former plant was dismantled and the site cleaned up. Energy Department
It is still uncertain how the Trump administration will regard public participation, public protest, and the rule of law at Rocky Flats and other Superfund sites. The new Energy Secretary, Chris Wright, is the former chief executive of a fracking company based in Denver, a known climate change denier, and was on the boards of EMX Royalty, a Canadian company that seeks royalties from extractive mineral mining, and Oklo, Inc., which designs small modular nuclear reactors. Wright is now responsible for overseeing atomic weapons production, cleanup of former weapons facilities, and US energy policy in general. How Wright will interact with Colorado peace activists and environmental protection groups concerned about the defunct plutonium-contaminated weapons facility at Rocky Flats is unclear. But the fight over the future of this legacy site appears far from over.
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