The former nuclear weapons plant northwest of Denver isn't causing any risks to humans, according to a report card out from the Department of Energy this week.

Rocky Flats' central area is still polluted, though, according to the 405 page report.

The federal government has been spending about three million dollars a year to remediate and monitor the Rocky Flats site.

That's where the radioactive triggers were made for the United States' nuclear bombs through the Cold War.

Work shut down in the early 1990's after the FBI and the EPA stepped in for what they called "environmental crimes."

Things like plutonium, uranium, other chemicals and heavy metals got into the ground after fires and spills.

The Department of Energy has been trying to clean up and contain pollution in the 1300 square acre area in the center of the site since.

This report says the remediation is working, but it also says the government will have to keep working into the foreseeable future.

Their next report is due out in 2022.

Surrounding that central area is a buffer zone that was used for security while the plant was active.

That area is doing well enough that the US Fish and Wildlife Service plans to turn it into a wildlife refuge next summer.