In early 1944, DuPont, the operating contractor at Hanford, foresaw the need for four chemical separation facilities. These facilities, designated the T and U plants at location 200-West and the B and C plants at location 200-East (the C plant was never built), would be located approximately ten miles south of the reactors.
The separation facilities at Hanford were massive scaled-up versions of the semi-works at Oak Ridge, each containing separation and concentration buildings in addition to ventilation (to eliminate radioactive and poisonous gases) and waste storage areas. Labor shortages and lack of final blueprints forced DuPont to stop work on the 200 areas in the summer of 1943 and concentrate its forces on 100-B, with the result that 1943 construction progress on chemical separation was limited to digging two huge holes in the ground.
Both 221T and 221U, the chemical separation buildings in the 200-West complex, were finished by December 1944. 221B, the counterpart in 200-East, was completed in the spring of 1945. Nicknamed "Queen Mary's" by the workers who built them, the separation buildings were awesome canyon-like structures 800 feet long, 65 feet wide, and 80 feet high containing forty huge process pools. The interior had an eerie quality as operators behind thick concrete shielding manipulated remote control equipment by looking through television monitors and periscopes from an upper gallery. Even with massive concrete lids on the process pools, precautions against radiation exposure were necessary and influenced all aspects of plant design.