Appeals Court Upholds EPA Approval of Radioactive Phosphogypsum Test Road in Polk County

A federal appeals court has upheld the Environmental Protection Agency's approval of an experimental road project in Polk County that uses phosphogypsum, a radioactive byproduct of phosphate fertilizer production, as a construction material. The Eleventh Circuit Court of Appeals issued its decision on August 12 in a case brought by the Center for Biological Diversity.

The three-judge panel ruled unanimously, holding that the EPA did not violate applicable regulations in approving the project and that the agency's reasoning was well supported and appropriately tailored to the specific proposal before it.

The road at issue is being built by Mosaic Fertilizer on company-owned private land as a demonstration project. The approval did not authorize general use of phosphogypsum in public road construction across Florida.

What phosphogypsum is

Phosphogypsum is the solid waste left over when phosphate rock is processed into fertilizer using sulfuric acid. Florida's phosphate industry, concentrated in the central part of the state, has produced enormous quantities of it over decades.

The material is radioactive because phosphate rock naturally contains uranium and radium, and those elements concentrate in the waste stream rather than in the fertilizer product. Radium decay produces radon gas, which is the principal pathway by which the material can pose a health risk.

Because of that radioactivity, federal regulations have generally required phosphogypsum to be stored in engineered stacks rather than used in construction. Those stacks, known locally as gypstacks, are among the most visible industrial features of Central Florida's phosphate district and have been the subject of environmental concern for decades.

Florida holds roughly a billion tons of stacked phosphogypsum, and the industry generates additional volumes annually. Finding beneficial uses for the material would reduce the volume requiring perpetual storage, which is the policy argument behind proposals like this one.

What the court decided

The Center for Biological Diversity challenged the EPA's approval on the grounds that the agency did not adequately address the risks phosphogypsum presents and that it relied on outdated data in reaching its conclusion.

The panel rejected both arguments. According to the ruling, the EPA conducted a multi-year review, found that Mosaic's proposal included the necessary information, and determined that risks to workers, nearby residents and the environment fell below applicable health thresholds.

The agency also concluded that using the material in the proposed road posed no greater risk than continuing to store it in a stack, and it imposed ongoing monitoring requirements as a condition of approval. The court found that reasoning adequately supported.

Judicial review of agency decisions of this kind is generally deferential. Courts examine whether an agency followed required procedures and whether its conclusions have reasoned support in the record, rather than substituting their own scientific judgment for the agency's.

The Florida context

Central Florida's phosphate district spans Polk, Hillsborough, Manatee, Hardee and DeSoto counties, and the industry has operated there for well over a century. It remains a significant regional employer and a major component of the state's agricultural supply chain.

The environmental record of phosphogypsum storage in Florida includes serious incidents. Sinkholes have opened beneath gypstacks, and the Piney Point facility in Manatee County required emergency wastewater discharges into Tampa Bay in 2021 when its containment was at risk of failure, an episode that contributed to significant water quality problems in the bay.

Those events form the backdrop against which environmental groups have opposed expanding uses for the material. Their argument has been that the state's history demonstrates the difficulty of managing phosphogypsum safely over long periods.

Industry and state officials have countered that finding productive uses reduces the volume requiring indefinite containment, and that engineered applications with monitoring requirements are preferable to perpetual stack storage.

What it means for Floridians

The immediate practical effect is narrow. The ruling permits a specific demonstration road on private company land to proceed under EPA-imposed monitoring conditions. It does not authorize phosphogypsum in public roadways.

The longer-term significance is regulatory. A demonstration project that operates with satisfactory monitoring results would strengthen the case for broader approvals, while adverse monitoring findings would undercut it. The data generated by the project is therefore the material question going forward.

Residents of the phosphate district have the most direct interest. Polk County communities sit closest to the project site and to the broader industrial footprint, and any expansion of phosphogypsum applications would affect them first.

For Floridians outside the district, the case matters primarily as a question of how the state manages a very large accumulated industrial waste stream that requires either permanent containment or approved beneficial uses.

Local impact across the state

Polk County hosts the demonstration project and a substantial share of the state's phosphate operations. The county's economy includes mining, agriculture, logistics and, increasingly, residential development along the I-4 corridor.

Manatee County continues to deal with the legacy of the Piney Point facility, where closure work has proceeded under state oversight following the 2021 emergency. That site remains the most cited example of what can go wrong with phosphogypsum containment.

Hillsborough County and Tampa Bay carry downstream water quality exposure. The bay's recovery from nutrient pollution has been a long-running regional environmental effort, and discharges from phosphate facilities have set that work back on more than one occasion.

Hardee and DeSoto counties, more rural and more directly dependent on the industry economically, have generally been more receptive to phosphate operations than the more urbanized counties downstream.

The regulatory history

Federal regulation of phosphogypsum has shifted more than once, and that history explains why the current case arose in the form it did.

The Environmental Protection Agency has regulated the material under air rules addressing radionuclide emissions, and the general framework has required stack storage rather than distribution. The rules include provisions allowing the agency to approve specific alternative uses upon a demonstration that the use is at least as protective of public health as storage.

That approval mechanism is what Mosaic used and what the Center for Biological Diversity challenged. The dispute was therefore not about whether phosphogypsum can ever be used outside a stack, which the regulations contemplate, but about whether the agency properly applied its own standard to this particular proposal.

Congress has separately directed attention to phosphogypsum in road construction through provisions in transportation legislation, and the question has been the subject of study requirements and industry advocacy over several years.

What the demonstration project will produce

The value of a demonstration project lies in the data it generates, and the monitoring conditions attached to the approval define what data that will be.

Radiation monitoring is the central element. Measurements of gamma radiation at the road surface and of radon flux from the material provide the direct evidence about whether exposure remains within the thresholds the agency evaluated.

Groundwater monitoring addresses the separate question of whether constituents leach from the material into the water table. Central Florida's surficial aquifer sits close to the surface in many areas, and leaching pathways are among the concerns environmental groups have raised regarding phosphogypsum applications.

Engineering performance is the third category. Whether the material performs adequately as a road base over time, under Florida's rainfall and temperature conditions, determines whether the application has practical value regardless of the environmental findings.

How gypstacks are built and closed

The storage method the road proposal is meant to reduce reliance on has its own engineering profile, and understanding it clarifies the tradeoff the EPA evaluated.

A phosphogypsum stack is an engineered impoundment built up over years as material is deposited, typically as a slurry. The stacks reach substantial heights and cover large areas, and they hold process water in ponds at the top.

That process water is the source of much of the environmental risk. It is acidic and contains dissolved constituents, and the volume held at a stack must be managed continuously through evaporation and treatment. Heavy rainfall adds volume that must be accommodated.

Closure requires capping the stack, managing the remaining water inventory and establishing long-term monitoring. The obligation does not end when a facility stops operating, which means financial assurance requirements are central to the regulatory framework.

Florida's experience at Piney Point illustrated what happens when those obligations are not met. The facility's containment deteriorated after its operator ceased operations, and the state ultimately conducted emergency discharges into Tampa Bay to prevent a catastrophic failure.

The competing arguments

Both sides of the phosphogypsum debate make arguments that are internally coherent, and the disagreement turns substantially on how to weigh different categories of risk.

Proponents of beneficial use argue that the alternative is not zero risk but perpetual storage, which carries its own hazards demonstrated by Florida's own history. On this view, distributing material into applications where it is bound in engineered structures reduces the concentrated risk that stacks represent.

Opponents argue that stacks, whatever their problems, are contained and monitored in known locations. Distributing radioactive material into roads places it in many locations where long-term monitoring is impractical and where future excavation or demolition could disturb it.

The regulatory question the court addressed was narrower than either argument. It asked only whether the EPA followed its own procedures and reached a supportable conclusion on this specific proposal, which the panel found it did.

The broader policy question remains open and will be shaped by monitoring results, further regulatory action and any subsequent litigation.

What's next

Monitoring data from the demonstration road will be collected under the conditions EPA attached to its approval. Those results will inform any future request to expand phosphogypsum use.

The Center for Biological Diversity has been an active litigant on phosphate industry issues in Florida over many years, and further legal action on related permits and approvals is possible. The organization's filings and EPA's docket materials are the authoritative record of the proceedings.

State-level regulation runs through the Florida Department of Environmental Protection, which oversees phosphogypsum stack permitting and closure in the state alongside federal requirements.

The full opinion in Center for Biological Diversity v. U.S. Environmental Protection Agency is available through the Eleventh Circuit Court of Appeals, which is the authoritative source for the court's reasoning.