The group Hanford Challenge says that delay is too long.
The U.S. Department of Energy on Friday presented the state of Washington with a plan for emptying the double-walled storage tank known as AY-102. The underground tank is located within the Hanford reservation near Richland.
The tank, the oldest of the giant double-walled tanks at Hanford, contains radioactive wastes left over from the production of plutonium for nuclear weapons.
The plan says pumping would not begin until March 2016 at the earliest.
Leaks have been found within the walls of the tank, but no waste is believed to have escaped into the ground.