- The federal government is working on a long-term plan to clean up dirty groundwater at an old uranium mill site near Moab, Utah.
- An estimated 16 million tons of radioactive waste sat for decades in a pile next to the Colorado River.
- Six national laboratories teamed up with the Department of Energy to figure out how to fix the pollution.
- A draft cleanup plan is scheduled to be submitted by 2027.
- Climate change and shrinking Colorado River flows make an already complicated problem even harder.
Friday, June 5, 2026 — The Department of Energy’s Moab site sits about three miles northwest of Moab in Grand County, Utah, right next to the Colorado River. Over the years, roughly 16 million tons of uranium mill tailings
piled up there. Mill tailings are the sandy radioactive leftovers from processing uranium ore. The pile sat in an unlined pit in the Colorado River’s floodplain. Liquids from the pile leaked down into the groundwater, contaminating it with ammonia, uranium, manganese, copper, sulfate, selenium, and arsenic.
Now the federal government is racing to finish a cleanup plan before the site changes hands between two branches of the Department of Energy. The stakes are high. The Colorado River runs right past the property, and contaminated groundwater is already leaking into it.
Moving the Pile.
Between 1988 and 1995, workers placed a temporary cover over the tailings pile. In 2001, the Department of Energy took ownership of the property and responsibility for cleaning it up. In April 2009, the Department of Energy began moving the tailings to a special disposal site at Crescent Junction, Utah. The cleanup at the surface is still underway and may be finished as early as 2028.
But moving the pile solves only part of the problem.
What Lies Underground.
Even after all the tailings are hauled away, contaminated soil remains underground. That dirty soil acts like a slow-release capsule, steadily feeding ammonia and uranium into the groundwater. The groundwater flows toward the Colorado River and eventually seeps into it.
The underground situation is complicated. Groundwater sits about 15 feet below the surface. Below that, at roughly 55 feet deep, lies a zone of salty brine water. Contaminants have leaked into both layers. The situation changes with the seasons. During normal conditions, groundwater flows toward the river. But during spring snowmelt runoff, the river pushes water backward into the aquifer, reversing the flow.
A 2005 federal report identified ammonia as the main pollutant in both groundwater and surface water. The Environmental Impact Statement for the project noted that the stretch of the Colorado River next to the site is protected critical habitat for endangered fish species. A Fish and Wildlife Service Biological Opinion was based on the Department of Energy’s commitment to conduct active remediation. To limit harm to endangered species, the 2005 report prescribed interim actions.
A Temporary Fix.
Since 2003, the Department of Energy has run a temporary system to keep the worst contamination away from endangered fish habitat along the river. The system has three parts. First, eight extraction wells pump dirty water out of the ground. Second, 10 injection wells push filtered river water underground to create a barrier between the pollution and the river. Third, a surface water diversion system delivers fresh water to sensitive stretches of the riverbank when young endangered fish are present.
Annual reports show the system works when it is running. The dirty water gets pumped out and sprayed on top of the tailings pile to keep down dust. But once the tailings are completely moved, there will be no pile left to spray water on. The temporary system will need to be redesigned or replaced. That is why the government needs a permanent plan.
Getting Expert Help.
In 2022, the Department of Energy called on the nation’s top scientists for help. The Network of National Laboratories for Environmental Management and Stewardship brought together experts from six national laboratories: Savannah River National Laboratory, Pacific Northwest National Laboratory, Sandia National Laboratories, Lawrence Livermore National Laboratory, Lawrence Berkeley National Laboratory, and Los Alamos National Laboratory.
During virtual meetings in the fall of 2022, scientists, engineers, and regulators split into three working teams. Team 1 tackled the overall strategy for writing the cleanup plan. Team 2 focused on understanding what is happening underground. Team 3 developed a list of possible cleanup methods.
The Nuclear Regulatory Commission, which has to approve the final plan, participated in the meetings. State agencies from Utah and officials from Grand County watched the process.
No Simple Solution.
The experts all agreed: the Moab site is what the Interstate Technology and Regulatory Council calls a “complex site.” That means no single method will solve the problem. The pollution is too widespread, the rock layers underground are too tangled, and the chemistry is too unpredictable for a simple fix.
Their top recommendation was something called “adaptive site management.” Instead of picking one solution and hoping it works, this approach treats cleanup as an ongoing, flexible process. Managers divide the site into zones. They set goals for each zone, try different methods, watch the results, and change course when needed. If something is not working, they switch to a new approach.
“Adaptive site management can and should be implemented immediately,” the collaboration report stated, noting that the approach “provides a framework for sequencing the other actionable recommendations” and “does not have prerequisites to implement.”
Understanding the Underground.
The single most important recommendation from the collaboration was to build a detailed computer model. This model would show how groundwater moves through the site and how contaminants travel with it. Most participants, including the Nuclear Regulatory Commission, agreed that this kind of model is essential for choosing the right cleanup strategy.
Federal regulations require it, too. If the final plan uses natural flushing, where clean water slowly pushes contaminants out over time, the law says that process must finish within 100 years.
But scientists still have major gaps in what they know about conditions underground. They do not fully know how much contamination sits in the deep brine zone, how fast it moves between the brine and freshwater layers, or how the river’s seasonal changes affect everything. The collaboration recommended more field work to fill in these gaps, including drilling, testing soil gases, and analyzing chemicals.
The amount of recommended investigation was so large that the experts suggested creating a new staff position just to coordinate all the data collection. They called it a technology portfolio manager.
Many Tools, No Single Answer.
Team 3 laid out nine possible cleanup methods. They range from simple approaches, like letting the aquifer flush itself over time, to more complex engineering, like injecting chemicals underground to lock contaminants in place or pumping and treating groundwater through filters.
Some of the ideas include covering contaminated soil with hardened local rock to stop rainwater from washing more pollution into the water table. Others involve injecting substances like calcium citrate and sodium phosphate to create underground barriers that trap uranium. One idea even suggests rerouting the channel of the Colorado River or Moab Wash to move critical fish habitat farther from the pollution.
None of these options have been picked yet. The experts said much more data collection and computer modeling must happen first before anyone can decide which methods will work best at this site.
Climate Change Makes Things Harder.
The collaboration pointed to climate change as an important factor that could change the entire cleanup picture. The Colorado River Basin has warmed faster than almost anywhere else in the lower 48 states. River flows have been dropping since 2000. Lower flows could mean less natural flushing of the aquifer. At the same time, climate change could bring more extreme storms, which might wash contaminants around in unexpected ways.
The scientists recommended that climate change be included in the computer model and in the design of any long-term solution.
What Happens Next.
According to the Department of Energy’s website, field work to fill data gaps is currently happening at the site. Once that work is done, scientists will have an updated understanding of conditions underground. Then a cleanup strategy will be developed with input from stakeholders.
A draft Groundwater Compliance Action Plan is scheduled to be submitted to the Nuclear Regulatory Commission in 2027. The commission must approve the plan before any permanent solution can be put in place.
The timeline matters because the Department of Energy’s Office of Environmental Management, which currently runs the site, plans to hand it off to the Office of Legacy Management after the surface cleanup is done. Legacy Management would then be responsible for the long, slow work of getting groundwater back to safe levels, protecting the Colorado River, and running whatever cleanup systems are in place.
For the communities downstream and for the endangered fish species that depend on clean water in this stretch of the Colorado River, the outcome matters. The question now is how long the cleanup will take and whether the plan can change fast enough as conditions shift and new information comes to light.
Pictured: Utah – River cleanup in Moab Area, October 2024, by MyPublicLands. Licensed under the Creative Commons Attribution 2.0 Generic license.
