DENVER (CN) — In rejecting an environmental group’s challenge, the 10th Circuit found neither increased public health risks nor controversy in a proposed trail change at the Rocky Flats National Wildlife Refuge, built around the site of a former nuclear weapon production facility in Golden, Colorado.

“The [U.S. Fish and Wildlife] Service relied on categorical exclusions to make the trail modifications in the 2018 environmental action statement. It did so after concluding no extraordinary circumstances existed that would prohibit the use of these exclusions,” wrote U.S. Circuit Judge Scott Matheson Jr. in a 44-page opinion published Tuesday.

The Barack Obama appointee added the Rocky Mountain Peace and Justice Center “has failed to show that the service’s reliance on the categorical exclusions to make the trail modifications was arbitrary or capricious.”

From 1952 to 1992, the Rocky Flats Plant produced an estimated 70,000 plutonium pits, the device responsible for detonating nuclear bombs. The plant closed after an FBI raid uncovered mishandling of radioactive materials and the U.S. Environmental Protection Agency declared it a Superfund site.

In 2001, Congress passed the Rocky Flats National Wildlife Refuge Act and allocated $7.7 billion over a decade to clean up the area with plans to open it to the public.

The 1,300-acre core of the refuge where the actual manufacturing took place has been designated a legacy site by the Department of Energy and will be closed indefinitely. But 11 miles of trails encircle the buffer zone, connecting the Rocky Mountain Arsenal National Wildlife Refuge northeast of Denver with the Rocky Mountain National Park just west of Boulder.

Boulder-based Rocky Mountain Peace and Justice Center sued the U.S. Fish and Wildlife Service in 2018 in effort to stop the refuge from opening to the public, citing concerns about the lack of recent environmental assessment given the site’s radioactive history.

A federal judge heard arguments and denied the group’s request to halt the project, finding the risk to the public was low. The national park opened to the public in September 2018.

When Fish and Wildlife proposed a new trail across the southwest boundary of the refuge near old clay and coal mines, the center filed a challenge asking for a new environmental impact statement. While the federal government did not consider the alteration to pose either increased health risks or controversy, the group begged to differ.

It argued newly built trails might pass through areas with higher plutonium counts, increasing health and safety risks for visitors and the surrounding community. The court however found the issue previously addressed by Fish and Wildlife’s 2004 environmental impact statement, which found the entire refuge generally safe for the public.

Based on the site’s cleanup standard of 50 pCi/g, a refuge worker might face an increased cancer risk of 1 in 133,300, assuming they work four hours indoors and four hours outdoors, 250 days a year for nearly 19 years. This measure increases visitor cancer risks to 1 in 227,000, assuming children spend 2 1/2 hours at the refuge 100 days out of the year for six years, and adults spend the same amount of time at the site for 24 years.

The environmental group further contended the development remained controversial, an issue the court also considered settled since the greatest controversy dated back to the site’s original plans, and not the latest trail change.

Senior U.S. Circuit Judge Paul Kelly, appointed by George W.H. Bush, rounded out the panel alongside Obama-appointed U.S. Circuit Judge Carolyn McHugh.