SPOKANE, Wash. (AP) — Workers on the Hanford Nuclear Reservation have finished cleaning up one of the nation's most contaminated radioactive waste sites, known as the 618-10 Burial Ground.

The U.S. Department of Energy said Thursday that the burial ground took eight years to clean up.

The 580-square-mile Hanford site is located near Richland in southeast Washington state. For decades it produced plutonium for nuclear weapons.

During the cleanup, workers retrieved more than 2,200 55-gallon drums, plus other waste, some of it buried more than 20 feet underground.

In total, workers removed more than 512,000 tons of contaminated soil and waste debris, which was taken to Hanford's hazardous-waste landfill.

Hanford was created by the Manhattan Project during World War II as the nation raced to produce an atomic bomb.