Important Review PaperA Quick Look at Plutonium Contamination from Rocky Flats

LeRoy More <[email protected]>


The first of the two nuclear bombs used against Japan was a uranium bomb dropped on the city of Hiroshima. The second bomb, which destroyed Nagasaki, was a plutonium bomb. U.S. authorities soon realized that plutonium bombs weighed less but had a bigger explosion, so they decided that all future U.S. nuclear bombs would be made with plutonium. The Austin Company of Cleveland, Ohio, was given the task of selecting a site for this plutonium work. They chose a place called Rocky Flats, 16 miles northwest of downtown Denver. They took wind readings at the former Stapleton Airport, where the wind blows north. This was a fatal mistake, because at Rocky Flats severe winds from the mountains carried debris, including tiny particles of plutonium southeast into suburbs and Denver.

High winds turned over a large truck on Hwy. 93 near Rocky Flats (Rocky Mountain News, Dec. 14, 1990)

There was a major fire at Rocky Flats in 1957 that released much plutonium into the environment, but the public was not informed. On May 11, 1969 (Mother’s Day), there was another large fire, which caught the attention of radiochemist Ed Martell of the National Center for Atmospheric Research in Boulder, who had worked on nuclear bombs tests in the South Pacific after World War II. He feared strong winds would carry lethal particles of plutonium toward unsuspecting people in the Denver area. He and a colleague collected samples and found plutonium deposits in soil up to  499 times average background concentrations from global fallout. He held a news conference, which was the beginning of public knowledge about Rocky Flats.

In 1970 P. W. Krey and E. P. Hardy of the Atomic Energy Commission, predecessor to the Department of Energy, came to Colorado from New York and collected samples.

Their map shows where heavy concentrations of plutonium were deposited. Added to their photo is a dotted red line: the route proposed for the Jefferson Parkway.

Later P. W. Krey published this map showing where plutonium from the 1969 fire was deposited throughout the Denver metro area. 

W. Krey, “Remote plutonium contamination and total inventories from Rocky Flats,” Health Physics, 1976, Vol. 10. 209-214.

The advantage of these images is that both Krey and Hardy are employees of the Atomic Energy Commission. They thus speak not as outsiders but as officials of the federal agency that produced nuclear weapons.

After the 1969 fire a Jefferson County Commissioner asked Carl  Johnson, recently hired Jefferson County Medical Director, whether it would be safe to live near Rocky Flats. He answered in two ways, first by sampling airborne dust for plutonium particles instead of plutonium in soil. He found far more plutonium than the state Health Department, which had sampled only soil. Second, he produced this map showing cancer incidence in three areas contaminated with plutonium from Rocky Flats and one area with no plutonium.

Johnson, “Cancer Incidence in an Area Contaminated with Radionuclides Near a Nuclear Installation,” AMBIO, 10, 4, October 1981.

              Area 1:                           16% more cancer than non-contaminated Area 4.

              Area 2:                           10% more cancer than non-contaminated Area 4.

              Area 3:                             6% more cancer than non-contaminated Area 4.

              Area 4:                           No plutonium deposits from Rocky Flats.

The cleanup the public wanted

In 1992, after it was decided that Rocky Flats would be closed to production, DOE created and funded the Rocky Flats Future Site Use Working Group. I was a member. They gave us one year to issue a report on what the public wanted at Rocky Flats. We recommended by consensus that plutonium in the Rocky Flats environment be cleaned to 0.04 picocuries per gram of soil, the quantity of plutonium deposited in the local environment from global fallout. In other words, we wanted all plutonium deposited from Rocky Flats removed. This proposal was totally rejected.

Without going into all the details, over an extended period DOE and the regulators (EPA and CDPHE) decided with no public input on three levels of cleanup:

  • Plutonium in the top 3 feet of soil would be cleaned to 50 picocuries per gram of soil (pCi/g ) – 12,500 X the 0.04 pCi/g the public sought.
  • Plutonium at a depth of 3 to 6 feet will be cleaned to between 1,000 and 7,000 pCi/g, with amount of remaining plutonium in soil dependent on size of the deposit.
  • Plutonium at a depth greater than 6 feet will not be cleaned but will remain. Numbers 2 and 3 allow to remain in soil far more plutonium than the public wanted.


The two biggest problems now remaining are the Rocky Flats National Wildlife Refuge and the proposed Jefferson Parkway. The Refuge opened to the public in September 2018. To date, seven school boards have said they would not take their students on field trips to the Refuge. Several groups continue to seek permanent closure of the Refuge.


Randy Stafford can provide details on the Jefferson Parkway,