HANFORD — The last water tower that once served Hanford's plutonium-production reactors along the Columbia River has come crashing down.

Workers were lifted to just below the tank of the 125-foot-tall water tower at D Reactor to attach a cable. Then a bulldozer pulled the 263-foot cable until the tower toppled.

"It was satisfying to see it pull away from the base," said Bob Smith, Washington Closure Hanford project director for deactivation and demolition.

As it hit the ground, the top popped off and a cloud of rust and dust billowed from the tank.

Although two water towers still remain in central Hanford, the D Reactor tower was the last of those to come down as the Department of Energy works to clean up the Hanford nuclear reservation along the river by 2015. Each of Hanford's nine reactors once had a tower.

"It's an indication of the continued progress we're making in cleaning up the river corridor and doing it safely, protecting the workers and the environment," Smith said.

The D Reactor tower was built during World War II and once was used as a backup water source for fire suppression. It originally had a redwood tank atop the pedestal, but by the early 1960s the wooden tank was replaced with a metal one that held 100,000 gallons of water.

It was used as a backup water source as recently as the 1980s.

Pulling down the tower required about 100 engineering calculations to do it safely, according to Washington Closure. In addition, power sources had to be disconnected and asbestos removed. The tower weighed 125 tons empty.

After it was pulled down, an excavator with shears cut it into pieces and the debris was taken to a landfill in the center of Hanford.

The tower was one of the tallest structures remaining along the Columbia River, so boaters may notice the changed skyline. It also was one of the last structures to come down in the area around the D and DR reactors.

D and DR reactors have been cocooned. They were torn down to little more than their radioactive cores, sealed up and reroofed to allow their radiation to partially decay over 75 years, when additional cleanup action may be taken.