GAO: Ambiguous rules and conservative land-use assumptions add billions to DOE nuclear cleanup costs

A newly released federal watchdog report says legal and regulatory ambiguity is slowing the Energy Department’s cleanup of nuclear waste from former weapons and research sites and adding billions of dollars to one of the government’s biggest long-term environmental liabilities.

In the report released Friday, the Government Accountability Office said Congress and federal agencies could accelerate the work by clarifying which regulators control key decisions and by using more realistic assumptions about how contaminated land and groundwater will be used in the future.

The stakes are enormous. The Energy Department, which is responsible for cleaning up sites created largely during World War II and the Cold War, estimates the mission could continue until about 2100 and cost between $641 billion and $840 billion, according to the GAO report, numbered GAO-27-107791.

GAO said the cleanup now proceeds under three major laws with different regulators and requirements: the Atomic Energy Act, which gives DOE authority over radioactive materials; the Resource Conservation and Recovery Act, or RCRA, which governs hazardous waste and is often implemented by authorized states; and CERCLA, the Superfund law used for contaminated sites.

That overlap is especially consequential because much of DOE’s waste is “mixed waste,” meaning it contains both radioactive and hazardous components. The radioactive portion is generally governed by federal nuclear law, while the hazardous portion can fall under state hazardous-waste programs approved by the Environmental Protection Agency.

GAO found that some state regulatory actions at DOE cleanup sites may go beyond state authority by addressing the radiological part of waste that is generally regulated by DOE under the Atomic Energy Act. According to the report, courts have recognized that DOE’s authority under that law can preempt some state actions, but the statutes and case law remain unclear, particularly when mixed waste is involved.

That uncertainty has real consequences for cost and timing. Experts GAO convened with the National Academies of Sciences, Engineering, and Medicine said disputes over federal and state authority have contributed to longer cleanup schedules and billions of dollars in higher federal costs. The report said DOE’s assistant secretary for Environmental Management described the current framework in June 2026 as a “regulatory morass.”

GAO identified a second major driver of cost: cleanup decisions based on unrealistic assumptions about future land and groundwater use. In some cases, the report said, DOE has agreed to cleanup standards designed for possible future residential use even when there were no plans for housing development. DOE also did not always evaluate the costs of less stringent cleanup tied to more realistic future uses, GAO said.

The report pointed to Rocky Flats in Colorado as an example of how those assumptions can shape costs. After Congress designated most of the site as a national wildlife refuge in 2001, estimated cleanup costs fell from about $23 billion under a residential-use assumption to about $10 billion.

GAO said similar issues arise in groundwater cleanup, which is often driven by assumptions that groundwater will eventually be used for drinking water even where that is unrealistic. The report also said experts told GAO that some contaminant standards applied to groundwater cleanup rely on outdated science.

Older cleanup agreements are another complication. GAO said some agreements negotiated in the 1990s, before the full extent of contamination was known, include hundreds of milestones DOE has struggled to meet.

To address the problems, GAO said Congress should consider clarifying the preemptive scope of the Atomic Energy Act in DOE cleanup and creating a mechanism for DOE to appeal to EPA when an authorized state RCRA program may be infringing on federal authority over nuclear waste. GAO also said Congress should give more specific direction on how future land-use assumptions should be incorporated into cleanup decisions.

Beyond congressional action, GAO said DOE and EPA should improve how cleanup choices are reviewed. In a poll of experts convened by GAO, all recommended that the two agencies create an interagency task force of experts to review high-priority cleanup decisions and areas of legal or regulatory disagreement.

DOE concurred with two GAO recommendations, including developing options related to groundwater cleanup and establishing the interagency task force. But it did not concur with GAO’s recommendation that DOE sites evaluate and document expected cost and schedule outcomes under multiple future land-use assumptions.

EPA also concurred with two recommendations, including clarifying guidance on future land use and establishing the task force. But the agency did not concur with GAO’s recommendation on developing options for certain radionuclide groundwater cleanup approaches.

The practical message of the report is that the cleanup challenge is not just a technical problem left over from the nuclear age. GAO said clearer rules on federal and state authority, combined with more realistic and risk-informed cleanup assumptions, could help speed the work and reduce costs that otherwise may burden taxpayers for decades.