Built in 1944, the U Plant stretches 810 feet long, 66 feet wide and 77 feet high. The U Plant was the third plutonium processing canyon built on the Site, after T Plant and B Plant.

Hanford’s U Plant was the third plutonium processing “canyon” built on the Hanford Site, after T Plant and B Plant. Stretching 810 feet long, 66 feet wide and 77 feet high, it was constructed in 1944. While originally designed to perform the chemical separations activities needed to extract plutonium from irradiated uranium fuel rods, it was determined after construction that T Plant and B Plant would be able to process enough plutonium. As a result, U Plant became a facility for training T Plant and B Plant workers.
 
In 1952, U Plant was given a mission to recover uranium from the waste generated in the plutonium extraction process. For six years U Plant crews removed uranium from the chemical separations process waste and then transferred that uranium to a support facility.
 
U Plant was placed in standby mode in 1958, as more efficient and technologically advanced plutonium processing canyons were built at Hanford. From 1958 through 1964, U plant was used to receive, decontaminate and maintain contaminated equipment from other processing facilities. After 1964, U Plant underwent some minor decontamination work but has remained virtually deserted.
 
In 2005 a landmark decision was reached between the Department of Energy (DOE), U.S. Environmental Protection Agency (EPA) and Washington State Department of Ecology regarding the final disposition of U Plant. The decision represents the first cleanup “pathway” for any plutonium processing canyon within the DOE complex and features innovative demolition methods that could save $200 million over the costs of traditionally tearing down buildings.
 
The decision requires a number of disposal and decontamination activities to take place involving wastes, equipment, piping, and individual facilities within U Plant. Ultimately the plan is to demolish U Plant in such a way that the walls are partially collapsed. A barrier composed of a mixture of sand, clay and silt will be constructed over the rubble and will function essentially as a giant sponge. When it rains or snows in the winter, the barrier will soak up the moisture and have sufficient moisture storage capacity to prevent water from entering into the underlying waste and potentially mobilizing contaminants toward groundwater. During spring, summer and fall, the moisture will be released back into the atmosphere through evaporation. The soil cap will be covered by vegetation and the barrier created by the rubble will prevent any rainwater or melting snow from pushing contaminants toward groundwater. The decision also calls for the EPA to monitor the barrier and review its protectiveness.

Some of the first demolition activities associated with the decision took place in 2010 and 2011. A cement-like grout has been pumped into the U Plant interior and has filled much of the canyon and locked any contamination in place in preparation for complete facility demolition at a later date.