Eleventh Circuit Upholds EPA Approval of Mosaic Phosphogypsum Road in Polk County

A three-judge panel of the U.S. Court of Appeals for the Eleventh Circuit has unanimously rejected a challenge to the Environmental Protection Agency's approval of a road built with phosphogypsum at Mosaic's New Wales facility in Polk County. The ruling, issued Aug. 12, holds that the EPA did not violate its own regulations and that its reasoning was supported and appropriately tailored.

The case was brought by the Center for Biological Diversity, which argued the EPA failed to adequately address the risks of phosphogypsum and relied on outdated data. The panel disagreed on both points.

Phosphogypsum is a byproduct of phosphate mining and fertilizer production. It is mildly radioactive and emits radon gas, and it has generally been required to be stored in engineered stacks rather than used in construction.

The panel's approach reflects the deference federal courts generally extend to agency technical judgments. When a challenge turns on whether an agency adequately assessed scientific risk, courts ask whether the agency considered the relevant factors and articulated a rational connection between the facts and its conclusion, not whether the court would have reached the same result. That standard makes challenges of this kind difficult to win on the science alone, and it is why litigants frequently focus instead on procedural defects or on whether the agency had statutory authority to act at all.

What the court decided

The panel held that the relevant EPA regulations unambiguously permit case-by-case approval of what the rules describe as other uses of phosphogypsum, including road construction, provided that health protections are satisfied. That was the central legal question, and the court resolved it in the agency's favor as a matter of regulatory text.

On the risk analysis, the court cited the EPA's estimates: cancer risk of less than 1 in 1 million for nearby residents and facility workers, less than 2 in 1 million for construction workers, and 2.7 in 10 million for truck drivers hauling the material. The panel noted that even the highest of those estimates was at least 45 times lower than the threshold the Center for Biological Diversity itself had proposed as acceptable.

That comparison did significant work in the opinion. When a challenger's own preferred safety standard is exceeded by a wide margin under the agency's numbers, the challenge to the adequacy of the analysis becomes difficult to sustain.

The volumes involved are difficult to convey without numbers. Producing one ton of phosphoric acid generates roughly five tons of phosphogypsum, and Florida's phosphate industry has operated at scale for more than a century. The resulting stacks are among the largest engineered structures in the state, some rising well over a hundred feet above the surrounding flat terrain and covering hundreds of acres each. They are visible from highways across Polk and Hillsborough counties, and they are permanent features of the landscape in a way that few industrial byproducts anywhere are.

What phosphogypsum is and why it is regulated

Phosphate rock contains naturally occurring uranium and radium. When the rock is processed into phosphoric acid for fertilizer, those elements concentrate in the calcium sulfate byproduct, which is phosphogypsum. Radium decays into radon, a radioactive gas that is a known cause of lung cancer.

The EPA has regulated phosphogypsum under the Clean Air Act's national emission standards for hazardous air pollutants since 1989, generally requiring it to be stored in stacks. Florida has hundreds of millions of tons of phosphogypsum in stacks across the state's phosphate district, primarily in Polk, Hillsborough, Manatee, and Hardee counties.

Those stacks are permanent liabilities. They must be capped, monitored, and maintained indefinitely, and they carry water management obligations because rainwater accumulating in stack ponds becomes acidic process water that cannot simply be discharged.

Florida's phosphate district also sits atop the aquifer system that supplies drinking water to much of the region, which is why groundwater monitoring is a standing permit condition at every stack. A sinkhole opened beneath a Mosaic stack at the New Wales facility in 2016, draining a substantial volume of contaminated process water into the Floridan aquifer before it was plugged. That incident, along with Piney Point, is why Central Florida residents tend to evaluate phosphate industry proposals against a memory of specific failures rather than against abstract risk estimates.

The Piney Point precedent

Florida's experience with phosphogypsum stack failure is why this issue carries weight here that it does not elsewhere. The Piney Point facility in Manatee County, an abandoned phosphate plant, experienced a liner breach in 2021 that forced the state to discharge more than 200 million gallons of contaminated process water into Tampa Bay to prevent a catastrophic collapse.

The discharge introduced large volumes of nitrogen and phosphorus into the bay, and a substantial red tide bloom followed that summer. Establishing direct causation between the discharge and the bloom is scientifically complex, but the sequence shaped public understanding of what phosphogypsum stacks represent.

Piney Point has since been undergoing closure with state funding. The episode is the reason the argument for finding beneficial uses of phosphogypsum, rather than accumulating it indefinitely, has advocates as well as opponents.

The distinction between test use on private property and general deployment on public roads is doing significant work in this dispute. The New Wales project is confined to Mosaic's own land, where access is controlled and exposure can be monitored. A public road built with phosphogypsum would involve utility crews digging into it, future resurfacing and demolition, and eventual disposal of the material when the road reaches end of life. Those downstream handling questions are largely unaddressed by an approval limited to a controlled test, and they are the substance of what opponents are concerned about.

The argument for road use

The case for using phosphogypsum in road construction is that stacks are not a solution. Every ton stored is a ton that must be managed permanently, and Florida's stacks continue to grow as long as phosphate mining continues.

Phosphogypsum has been used in road construction in other countries, and proponents argue that encapsulating the material in a roadbed, where it is covered and stabilized, poses less long-term risk than storing it in stacks that can fail. The New Wales project is a test on Mosaic's own private property rather than on a public road.

Opponents argue that approving test use establishes a pathway toward broader deployment, and that radioactive material should not be distributed across the landscape regardless of the calculated risk per individual. The Center for Biological Diversity's position has been that the EPA's analysis relies on data too old to support the conclusion.

Fertilizer supply is the broader context that makes this an economic question and not only an environmental one. Phosphate is one of three primary crop nutrients and has no synthetic substitute, and global supply is concentrated in a small number of countries. Florida's production is a meaningful share of United States output, which links the disposition of phosphogypsum to domestic agricultural input costs. That connection is why the industry retains political support in Florida across administrations even as its environmental record generates sustained local opposition.

What it means for Florida

Polk County sits at the center of Florida's phosphate district, and the industry is among the region's major employers. Mosaic is one of the world's largest phosphate producers, and its Florida operations supply fertilizer to agricultural markets globally.

The immediate practical effect of the ruling is narrow: a test road on a company's private property proceeds. The broader significance is that a federal appeals court has confirmed the EPA has authority to approve case-by-case beneficial uses, which is the legal foundation any future expansion would rest on.

For Central Florida residents living near phosphate operations, the ruling does not change day-to-day conditions. The stacks remain, the water management obligations remain, and the regulatory framework governing them is unchanged.

The Eleventh Circuit's docket this year illustrates the range. Alongside the phosphogypsum decision, the court issued rulings in August involving federal criminal appeals out of Florida districts, insurance disputes, and railroad regulation. Federal appellate outcomes shape Florida environmental policy without any state actor being party to the case, because so much of the regulatory framework governing Florida land, water, and air originates in federal statute administered by federal agencies.

The federal courts and Florida environmental cases

The Eleventh Circuit, which covers Florida, Georgia, and Alabama, handles federal appeals arising from Florida environmental disputes. Its rulings shape how federal environmental statutes are applied across the state.

That docket has been active. The court has also handled cases involving Florida East Coast Railway and the Federal Railroad Administration, and it operates alongside a broader set of federal actions affecting Florida's environment, including Endangered Species Act rule changes taking effect this month that conservation groups have challenged in court.

Federal environmental litigation moves slowly and frequently produces mixed results. A single panel ruling on a single regulatory approval does not settle the underlying policy question about what Florida should do with hundreds of millions of tons of phosphogypsum.

Public participation channels remain open even after litigation concludes. EPA rulemakings on phosphogypsum use are subject to notice and comment, and the Florida Department of Environmental Protection holds its own permitting processes for stack construction, closure, and water management with associated public comment opportunities. Those state proceedings are frequently where the practical conditions attached to phosphate operations are set, and they receive substantially less public attention than federal litigation does.

What's next

The Center for Biological Diversity could seek rehearing before the full Eleventh Circuit or petition the U.S. Supreme Court, though neither is likely to be granted in a case turning on regulatory interpretation and agency risk analysis.

The test road at New Wales proceeds under the EPA approval. Monitoring data from the project would be the evidence base for any future decisions about broader phosphogypsum road use, and that data will accumulate over years rather than months.

Florida's phosphate stack inventory continues to be regulated by the EPA under the Clean Air Act and by the Florida Department of Environmental Protection under state permitting. Piney Point closure work continues in Manatee County.