RICHLAND — A factory that produced two-thirds of the nation’s Cold War-era plutonium for nuclear weapons has finally been completely demolished.

After 40 years of operations, and 20 years of often-dangerous cleanup work, crews recently finished demolishing the Plutonium Finishing Plant’s main processing facility at the Hanford Nuclear Reservation.

The news was announced Wednesday by the U.S. Department of Energy, which owns the sprawling Hanford site near Richland, Washington.

“Removal of this iconic building forever changes the landscape at the Hanford site,” said Tom Teynor, project director for the demolition.

The main processing facility was nicknamed “Z-Plant,” because it was the last stop in plutonium production at Hanford. It operated from 1949 to 1989 and contained two processing lines where workers created hockey puck-sized plutonium “buttons” for shipment to nuclear weapons-manufacturing facilities. Plutonium is a key ingredient in nuclear weapons.

Plutonium production left the facility highly contaminated with radioactive and other hazardous materials.

Decades of demolition preparations included decontaminating and removing about 200 pieces of plutonium processing equipment, 1.5 miles of ventilation piping, asbestos and other hazards.

Energy Department contractor CH2M HILL Plateau Remediation Company was responsible for the demolition.