HANFORD — Hanford workers have demolished the vaults built into the base of Gable Mountain during World War II to hold the nation's earliest supply of liquid plutonium.
Work next will be done to restore that part of Gable Mountain to the natural condition that the tribes remember.
"It will look exactly as it did before 1944 when they used it," said Jamie Zeisloft, Department of Energy project manager. "We will have reversed the hands of time."
The vault structure included a retaining wall where guards were stationed at two sets of doors into the two 30-foot-long vaults that extended underground into the slope of the mountain.
They were used for just three years -- 1944 to 1947. At that time, plutonium produced at the Hanford nuclear reservation was stored in containers shaped like bowling pins, said Michele Gerber, a Richland historian.
The liquid then was sent to Los Alamos, N.M., for further processing to be used in the nation's nuclear weapons program. In later years, the liquid was converted to metal buttons the size of hockey pucks at Hanford.
As with many of Hanford's structures, the vault complex would be converted to other uses. It stored drums holding equipment contaminated with radioactive sodium, Zeisloft said.
Records also show the complex later was used to store explosives and ammunition and for seismic testing, said Todd Nelson, spokesman for Washington Closure Hanford. In the 1970s, scientists used it to store soil samples for the long term study of the effect of plutonium in soil and plants.
The original cleanup plan for the vaults called only for scraping plutonium contamination off the inside of concrete walls to decontaminate the vaults, Zeisloft said.
But Gable Mountain holds an important place in the culture of area tribes. Tribes and bands, including the Wanapum, Yakamas, Nez Perce and Umatillas, wanted Gable Mountain to be restored to its pre-Hanford condition.
"It's a very sacred place recognized by all plateau people," said Rex Buck, leader of the Wanapum band. "We definitely needed it to be restored to the full capacity. It is highly significant for our beliefs and the way we take care of the land."
Tearing out the vault complex also reduced risk to workers from the contaminated dust created by scraping the walls.
Washington Closure Hanford instead applied fixative to the contaminated walls, excavated the hillside down to the vaults, and then used heavy equipment to demolish the concrete structure. The debris has been hauled to the Environmental Restoration Disposal Facility, a lined landfill for low level radioactive waste in central Hanford.
The work area was fenced before work started to minimize the area disturbed by the work. At the tribes' request, an asphalt road to the vaults also was taken out.
Now the soil is being sampled, and if the results come back clean, the area will be back filled, recontoured and planted with the seeds of native shrub steppe vegetation in consultation with the tribes. The total project will cost about $750,000.