DOE sees slower cleanup of uranium in groundwater on Wind River Indian Reservation

June 2012 Uranium Distribution in the Surficial Aquifer at the Riverton Site.
The heaviest concentrations of uranium are found in groundwater in the highest of three aquifers. Concentrations of uranium increase as the groundwater flows downhill, to the southeast, toward the Little Wind River. (Courtesy of Department of Energy — click to enlarge)
By Ron Feemster
— July 11, 2013

A new report by the Department of Energy suggests that cleaning the soil and groundwater near a Cold War-era uranium mill on the Wind River Indian Reservation may take longer than the 100 years allowed under Environmental Protection Agency regulations.

The 100-year clock began ticking 24 years ago when a 72-acre field of tailings was removed from the site near Riverton. The tailings — a mixture of crushed rock and water left over after uranium is extracted from ore — were deposited between 1958, when the mill began operation, and 1963, when it closed. The DOE carted away the tailings in 1989 and replaced them with clean fill to a depth of four feet.

William Dam (click to enlarge)
William Dam, a DOE hydrologist and the site manager, says new lab experiments suggest the soil retains more uranium than scientists earlier believed. (Click to enlarge)

The DOE is allowing the downhill flow of ground water to naturally flush the contaminants from the soil into the aquifer nearest the surface. That aquifer drains into the Little Wind River at about one-quarter cubic foot per second, according to the report, while the river flows at an average rate of 579 cubic feet per second, almost instantaneously diluting the groundwater to safe levels.

As WyoFile reported last month, the DOE expected the natural flushing process to be completed by 2089, as the EPA regulation requires. However, new computer modeling suggests that the process will take longer than originally calculated.

“The soil is more sticky than we thought,” said William Dam, a DOE hydrologist and the site manager. “Before we thought it was more like Teflon. It’s really more like Scotch Tape.”

Less uranium adheres to rocks and larger objects in the soil (the Teflon), primarily because the surface area of these soil particles is low compared to the amount of space they take up. Laboratory experiments have shown that more uranium sticks to clay, silt and some organic matter, said Dam, because these substances are made up of fine particles with greater surface area in a smaller volume. Uranium bound to these particles (the Scotch Tape) is released more slowly into the ground water.

A great deal of new information came to light studying the way soil is cleaned when the area floods, as it did in 2010. The groundwater rises and uranium comes off the soil particles and dissolves in the water. The area contaminated with these substances is called the plume. When flooding occurs, the concentration of contaminants in the plume increases, but it falls rapidly.

But after doing laboratory tests to measure the rate at which uranium detaches itself from small soil particles, Dam and his team believe that it may take longer to clean contaminants from the soil by flooding and flushing.

Preliminary results from an epidemiological survey on the reservation indicate that higher cancer rates may be related to the presence of uranium contamination, although more data is needed to complete the study.

Figure 19
The seven largest floods of the Little Wind River since the plant was shut down. Four of the floods, including the largest in 1963, occurred before the Department of Energy removed the tailings in 1989. (Courtesy of Department of Energy — click to enlarge)

The largest flood since the mill was built occurred in 1963, the year the tailing pile was at its largest and freshest. The ground water rose even higher in that flood 50 years ago than it did in 2010. That flood may have played a major role in the original contamination of the ground water, Dam speculates, although no measurements were taken at the time.

More floods are likely in the 76 years remaining in the EPA’s 100-year timetable for natural flushing. The report forecasts that the remediation could still be going on when the EPA clock runs out.

“Apparently DOE’s more extensive monitoring and modeling has cast doubt on their projection that the contaminants would flush to below acceptable limits within the 100 year timeframe, raising the possibility that they may need to pursue other strategies,” said David McIntyre, spokesman for the U.S. Nuclear Regulatory Commission, which enforces the EPA regulations. “Should DOE decide to make changes to their groundwater management plan, they would need to come to us for approval. That’s essentially all we can say at this point.”

In the meantime, the data collection at sample wells and surface water bodies continues on the reservation. Dam emphasizes that the alternative water supply system furnishes clean, safe drinking water to the community near the plume. A new cooperative agreement with the Eastern Shoshone and Northern Arapaho tribes was signed in April, which allows the tribal Wind River Environmental Quality Council to help monitor the water and soil quality. WREQC has been invited to meet with DOE to discuss the report at its regional headquarters in Grand Junction, Colo., although the exact date has not been set. A WREQC representative did not return calls for this story.

— Ron Feemster covers the Wind River Indian Reservation for WyoFile in addition to his duties as a general reporter. Feemster was a Visiting Professor of Journalism at the Indian Institute of Journalism & New Media in Bangalore, India, and previously taught journalism at Northwest College in Powell. He has reported for The New York Times, Associated Press, Newsday, NPR and others. Contact Ron at

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  1. A few of us who have worked on the Riverton UMTRA site have said for more than a decade that the soils were acting as a reservoir for contaminants. We were ignored by three previous DOE site managers. Maybe the Riverton site and the Tribes have finally gained the attention of someone with some integrity.