The Rocky Flats Plant was a U.S. manufacturing complex that produced nuclear weapons parts in the western United States, near Denver, Colorado. The facility's primary mission was the fabrication of plutonium pits, which were shipped to other facilities to be assembled into nuclear weapons. Operated from 1952 to 1992, the complex was under the control of the U.S. Atomic Energy Commission (AEC), succeeded by the Department of Energy (DOE) in 1977.

Pondcrete is a mixture of cement and sludge. Its role is to immobilize hazardous waste and, in some cases, low-level and mixed-level radioactive waste, in the form of solid material. The material was used by the United States Department of Energy and its contractor, Rockwell International, in an attempt to handle the radioactive waste from contaminated ponds in the Rocky Flats Plant for burial in Nevada desert. Portland cement is mixed with sludge to solidify into “pondcrete” blocks and placed into large, plastic lined boxes. The sludge is taken from solar evaporation ponds which are used to remove moisture from waste materials, therefore reducing their weight. To do this, liquid waste is poured into artificial, shallow ponds. The waste is heated by solar radiation and any moisture is evaporated, leaving behind the waste. These ponds contained low level radioactive process waste as well as sanitary sewage sludge and wastes, which categorize them and the Pondcrete as a mixed waste.