About 60,000 cubic meters of the 240,000 cubic meters (or around 25%) of the waste buried in the Radioactive Waste Management Complex came from the Rocky Flats weapons plant near Denver, Colorado. Established in 1951, Rocky Flats processed plutonium and other materials into detonators, or triggers, for nuclear weapons. Rocky Flats waste makes up most of the plutonium-contaminated waste in Idaho.

In 1993, President Clinton ended Rocky Flats nuclear weapons production mission. The site then shifted its focus to cleanup, waste disposal and decommissioning of equipment and buildings. After cleanup to meet certain standards was achieved, DOE certified Rocky Flats cleanup to be complete in 2005. The Rocky Flats Site is now a national wildlife refuge. Although cleanup of Rocky Flats contamination in Colorado is complete, DOE must still address the cleanup challenges posed by Rocky Flats waste shipped to Idaho.

In 1954, Rocky Flats' first full year of production, 200 barrels of plutonium-contaminated waste were shipped to Idaho each month. By 1956, 300 barrels were sent to Idaho each month; and by 1957, 400 barrels were sent to Idaho each month.

Typical waste shipments from Rocky Flats included solidified sludges from equipment cleaning, retired molds used to shape the plutonium metal, used filters, and worker's clothing. Prior to 1970, Rocky Flats waste sent to Idaho was buried in the SDA. After 1970, it was placed in above-ground storage. DOE assured the State that Rocky Flats waste would begin leaving Idaho when the Waste Isolation Pilot Plant (WIPP), a geologic repository, was opened in New Mexico in 1988.

In October 1988 when WIPP failed to open as scheduled and no opening was in sight, Idaho Governor Andrus ordered the Idaho State Police to stop further Rocky Flats shipments to Idaho. In December 1989 Rocky Flats shut down production to deal with safety and management issues. Due to latter DOE policy changes the Rocky Flats nuclear weapons production mission never restarted. So after October 1988, no additional Rocky Flats waste has come to Idaho.