The 903 Pad: Reconstructing a Major Plutonium Release from Rocky Flats

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One of the most significant contamination events in Rocky Flats history did not begin with a fire or explosion. It began with drums of plutonium-contaminated waste oil stored outdoors.

A 1996 study published in Health Physics reconstructed the release of plutonium from an area of the Rocky Flats Plant known as the 903 Pad. The research was conducted as part of a Colorado Department of Public Health and Environment effort to reconstruct historical contaminant releases and estimate potential doses to members of the public.

What Happened at the 903 Pad?

During the 1950s and 1960s, 55-gallon drums containing waste oil contaminated with plutonium and uranium were stored outside at the 903 Pad. Over time, some of the drums corroded and leaked. The contaminated oil entered the surrounding soil. According to the study, wind subsequently picked up contaminated soil particles and carried them beyond the Rocky Flats property boundary.

Historical dose-reconstruction records provide additional context: widespread drum corrosion and leakage was discovered in 1964. By 1967, more than 5,000 drums were stored at the pad, including thousands containing plutonium-contaminated material. The drums were eventually removed and the area was covered with asphalt.

Researchers Reconstructed the Release

Because the releases had occurred decades earlier, researchers could not simply measure what had been in the air at the time.Instead, they combined environmental measurements collected during the 1960s and 1970s with an atmospheric transport model designed to estimate how contaminated dust could have moved through the air. The researchers then reconstructed both airborne plutonium concentrations and deposition outside the plant for use in estimating potential radiation doses.

An Estimated Seven Curies Released Off-Site

The study's best estimate was that approximately 0.26 terabecquerels—about 7 curies—of plutonium were released to areas beyond Rocky Flats-owned property as a result of the 903 Pad contamination. The study estimated that the highest predicted off-site effective dose associated with the release was approximately 72 microsieverts, or 7.2 millirem.

Those numbers should be understood for what they are: historical reconstruction estimates based on environmental data and atmospheric modeling. They are not measurements of the dose received by any particular person, nor do they establish that an individual's illness was caused by the release.

Evidence of Off-Site Movement

The importance of the 903 Pad extends beyond the modeled release estimate. Federal environmental records later described a plume of elevated plutonium and americium concentrations in surface soils extending east from the 903 Pad and beyond the Rocky Flats property boundary. Those records identified windblown material from the 903 Pad as the primary source of that pattern.That history helps explain why geography and prevailing winds remain so important when understanding Rocky Flats.

Why This Study Matters

The 903 Pad is an important reminder that releases from Rocky Flats did not occur only during dramatic accidents. Here, contamination developed over years through waste-storage practices, leaking drums and the movement of contaminated soil by Colorado's strong winds.

The 1996 study is particularly valuable because it attempted to reconstruct how much plutonium left the plant property and how it may have been transported into surrounding areas.

It does not answer every question about individual exposure or community health.

It does document that plutonium-contaminated material from Rocky Flats was transported beyond the plant boundary—and provides a peer-reviewed estimate of the magnitude of that release.

Source: T.R. Mongan, S.R. Ripple and K.D. Winges, “Plutonium Release from the 903 Pad at Rocky Flats,” Health Physics, Vol. 71, No. 4, 1996, pp. 522–531. PMID 8830753. DOI: 10.1097/00004032-199610000-00010.