The toll road would cross a buffer zone on the east side of Rocky Flats, a former nuclear weapons plant northwest of Denver. Broomfield City Council announced it was halting efforts to find a private partner for the project and a city statement said that "the Parkway is not moving forward at this time."
The long-sought road would have eventually completed the 470 beltway around the perimeter of metro Denver.
Plutonium triggers for nuclear warheads were manufactured at the former plant from 1952 to 1989. Later, the manufacturing site underwent a $7 billion cleanup and was turned into a wildlife refuge.
State officials announced in August that a soil test found plutonium levels five times higher than the cleanup standard, but a second test found much lower levels. Officials were seeking more information on the results.
The contentious site remains a flashpoint with activists who have launched several lawsuits to unearth documents on the original investigation and to shut the preserve to human activity. Trails at the national wildlife refuge opened in September 2018.