Plutonium Detected in Air Filters Near Rocky Flats as Boulder County Reconsiders Greenway Project

The discovery of Rocky Flats-derived plutonium in air-filter samples collected along Indiana Street has renewed concerns about plans to expand the Rocky Mountain Greenway trail system near the former nuclear weapons plant.

The Rocky Mountain Greenway Project began in 2016 as an effort to connect three national wildlife refuges—Rocky Mountain Arsenal, Two Ponds and Rocky Flats—through a regional trail network. Plans include an underpass connecting the Rocky Flats National Wildlife Refuge to Boulder County open space and an overpass linking Westminster trails to the Greenway.

During gale-force winds on April 6, chemist and University of Denver professor Michael Ketterer joined retired FBI agent Jon Lipsky to collect airborne dust near Rocky Flats. Lipsky led the 1989 FBI raid of the plant, which helped bring nuclear weapons production at the site to an end.

Ketterer and Lipsky reported seeing large clouds of windblown dust originating from the Rocky Flats Central Operable Unit, the surrounding buffer zone or both. Two air filters were placed along Indiana Street while strong winds were blowing from the west.

The samples were sent to the radiochemistry laboratory at Northern Arizona University. According to Ketterer, plutonium was detected in all six laboratory preparations made from the two Indiana Street air-filter samples.

The laboratory identified plutonium-239 and plutonium-240. Ketterer said the ratio of the two isotopes created a distinctive “fingerprint” connecting the material to the former Rocky Flats nuclear weapons plant.

The samples reportedly measured between 0.15 and 1.19 picocuries of plutonium per gram of filter ash. The article compared the findings with Colorado’s construction standard of 0.9 picocuries per gram for soil, meaning the highest reported measurement exceeded that benchmark. The measurements came from airborne material captured by filters, however, rather than from conventional soil samples.

Ketterer warned that construction and increased recreational use could disturb contaminated soil and make it more vulnerable to erosion. Foot traffic, bicycles, animals and excavation could potentially loosen surface soil, allowing radioactive particles to be carried beyond the refuge by wind or other means.

Lipsky raised additional concerns about excavation required for the proposed trail crossings. He questioned what protections would be provided to construction workers and nearby communities if deeper soil containing radioactive contamination were disturbed.

Plutonium is a radioactive material that can increase the risk of lung, liver and bone cancer when it enters the body, particularly through inhalation. Plutonium-239 also has a half-life of approximately 24,000 years, making contamination at Rocky Flats a long-term public-health and environmental concern.

Boulder County Reconsiders Its Involvement

Boulder County entered an intergovernmental agreement supporting the Greenway Project in 2016. Other participating governments include Arvada, Boulder, Broomfield, Jefferson County and Westminster.

In January, Boulder County commissioners voted to oppose public recreation at Rocky Flats. That resolution did not automatically remove the county from the Greenway agreement.

Following the air-filter findings, commissioners reportedly sought legal advice about the consequences of remaining in or withdrawing from the agreement. An executive session concerning the Greenway agreement was later held, but details were not released because the discussion was protected by attorney-client privilege.

The project has also faced legal challenges. The Town of Superior previously sued over modifications to the refuge’s trail plans, alleging that the U.S. Fish and Wildlife Service failed to complete a required environmental review. A federal judge ruled against Superior in 2021.

Physicians for Social Responsibility Colorado subsequently filed another lawsuit seeking to block trail construction in and around Rocky Flats. That litigation was still pending when the article was published.

Why These Findings Matter

The detection of Rocky Flats-derived plutonium in airborne material raises an important question: Should public agencies promote construction and increased recreation near the former nuclear weapons plant when plutonium can still be detected in windblown dust?

For Rocky Flats Downwinders, the findings reinforce the need for independent environmental testing, transparent public disclosure and a precautionary approach to construction and recreation around the site.

Communities deserve complete information about potential exposure before additional trails, crossings or recreational projects are approved.

Source: “Plutonium found in Indiana Street air filters near Rocky Flats; Boulder Commissioners reconsider trail project,” Colorado Community Media.