Federal Appeals Court Clears the Way for a Phosphogypsum Test Road in Polk County

A federal appeals court has cleared the way for a test road built from phosphogypsum, the mildly radioactive byproduct of Florida's phosphate fertilizer industry, rejecting an environmental group's challenge to the Environmental Protection Agency's approval of the project.

The United States Court of Appeals for the Eleventh Circuit issued its decision on August 12, 2026, in Center for Biological Diversity v. U.S. Environmental Protection Agency, case number 25-10515. A three-judge panel unanimously denied the petition.

The ruling permits the Mosaic Company to proceed with a one-mile test road at its New Wales facility in Polk County, using phosphogypsum as a construction material on the company's own private property.

What the court decided

The panel held that the EPA did not violate its own regulations in approving the project. The court found that the relevant rules unambiguously permit case-by-case approval of other uses of phosphogypsum, including road construction, provided that health protections are adequate.

The court also concluded that the agency's reasoning was well supported and appropriately tailored to the specific request before it, rather than constituting a broad reopening of restrictions on the material.

The distinction matters legally. The Center for Biological Diversity argued that EPA's approval departed from the regulatory framework governing phosphogypsum. The court read the regulations as containing an explicit mechanism for case-by-case authorization, which meant the agency was operating within rather than around its rules.

Mosaic received permission from the EPA in 2024 to use phosphogypsum on its private property, and the litigation followed that approval.

What phosphogypsum is

Phosphogypsum is what remains after phosphate rock is processed into phosphoric acid, the base input for most agricultural fertilizer. Florida is the center of that industry in the United States, and the state's phosphate deposits have supported it for more than a century.

The material is radioactive because phosphate rock naturally contains uranium and radium, which concentrate in the byproduct rather than passing into the fertilizer. Phosphogypsum also contains heavy metals and residual acidity.

Because of the radioactivity, federal regulation has generally required phosphogypsum to be stored rather than used. The storage method is the phosphogypsum stack, an engineered mound that can rise to several hundred feet and cover hundreds of acres, typically with a process water pond on top.

Florida holds a large volume of the material in these stacks, and the industry produces more with each ton of fertilizer manufactured. The economics of finding a beneficial use are therefore substantial, since stack construction and perpetual maintenance are ongoing costs with no end point.

The risk numbers

The EPA's assessment estimated cancer risk at less than 1 in 1 million for nearby residents and facility workers, and at less than 2 in 1 million for construction workers. For truck drivers hauling the material, the agency estimated a risk of 2.7 in 10 million.

Those figures sit within the range the agency generally treats as acceptable for regulatory purposes, which is typically framed as a lifetime excess cancer risk between 1 in 1 million and 1 in 10,000.

Critics have raised methodological objections rather than disputing the arithmetic. The concerns center on whether a one-mile test road on private property adequately models the exposure pathways of widespread public road construction, whether the assessment accounts for the material's behavior over the multi-decade life of a roadway, and whether groundwater migration under Florida's specific hydrogeology was fully characterized.

The sinkhole history

The New Wales site carries a specific history that shapes how the project is viewed locally.

In 2016, a sinkhole opened beneath Mosaic's phosphogypsum stack at New Wales, the same facility where the test road is located. The collapse sent millions of gallons of contaminated process water into the Floridan aquifer, the primary drinking water source for much of the state.

Florida's geology makes such events a persistent risk. The peninsula sits on limestone that dissolves in acidic water, producing the karst topography responsible for the state's springs, its caves and its sinkholes. Heavy structures placed on that geology, particularly structures holding acidic water, carry inherent subsidence risk.

Separately, the Piney Point facility in Manatee County, a former phosphate plant, has required emergency discharges into Tampa Bay when its stack containment threatened to fail, releasing nutrient-laden water into a bay already managing water quality problems.

That history is why phosphogypsum proposals in Florida draw scrutiny disproportionate to the size of any individual project.

What it means for Floridians

The immediate practical effect is narrow. The approved project is a one-mile road on private industrial property, not a public highway, and it is structured as a test that will generate data on the material's performance.

The broader significance is precedential. If the test road performs acceptably and the monitoring data supports it, the pathway toward broader use of phosphogypsum in road construction opens, which would change the disposal calculus for an industry sitting on an enormous stockpile.

For Polk County residents, the near-term issue is monitoring. Any beneficial-use authorization carries conditions, and the value of a test project depends on whether the resulting data is collected rigorously and made public.

For Floridians generally, the aquifer is the shared stake. The Floridan aquifer supplies drinking water across much of the state, and the 2016 sinkhole demonstrated that industrial containment failures at these facilities reach it directly.

Florida's phosphate industry

The dispute over a one-mile test road sits on top of an industry that has shaped central Florida's landscape and economy for well over a century.

Florida's phosphate deposits, concentrated in a region historically known as Bone Valley across Polk, Hillsborough, Hardee, Manatee and DeSoto counties, have supported mining since the late nineteenth century. The state has been among the world's leading sources of phosphate rock, the raw input for the fertilizer that supports global food production.

Mining reshapes the land. Draglines strip overburden to reach the phosphate matrix, and the reclamation that follows is regulated by the Florida Department of Environmental Protection with requirements that have tightened substantially over the decades. Older mined lands, reclaimed under earlier standards or not at all, remain visible across the region.

Processing is where phosphogypsum originates. Converting phosphate rock into phosphoric acid produces roughly five tons of phosphogypsum for every ton of acid, which is why the stockpile grows continuously as long as production continues.

The industry employs thousands of Floridians directly and supports a larger supplier and transportation network, including rail and port operations that move product to domestic and export markets.

The regulatory history of phosphogypsum

Federal restrictions on phosphogypsum date to EPA rulemaking under the Clean Air Act addressing radionuclide emissions.

The agency's rules generally require the material to be placed in stacks rather than distributed, with narrow exceptions for research and for agricultural use in specified circumstances. The stated purpose is limiting public exposure to radium and its decay products, including radon.

The road use question has been raised repeatedly. Proponents have pointed to use of similar materials in road construction in other countries and have argued that encapsulation within a roadbed limits exposure pathways. Opponents have pointed to the difficulty of controlling material once it enters general construction use, to the potential for leaching into groundwater and to the eventual demolition and disposal of roads containing the material.

The regulatory approach has shifted between administrations. An approval issued during one administration was subsequently withdrawn, and the current authorization to Mosaic for a test road on its own property represents a narrower approach than a general authorization for public road construction would.

The Eleventh Circuit's reading, that the regulations explicitly permit case-by-case approval of other uses, is what preserved this particular authorization.

What Polk County residents face

Polk County sits at the center of the phosphate industry and carries both its economic benefits and its environmental legacy.

The county's employment base includes mining and processing operations alongside logistics, agriculture and a growing residential population driven by its position along the Interstate 4 corridor between Tampa and Orlando.

Water is the shared concern. The Floridan aquifer underlies the region, and phosphate operations are substantial water users as well as potential contamination sources. The Southwest Florida Water Management District regulates withdrawals and monitors groundwater quality across the area.

Sinkhole risk is elevated across the phosphate district because of the same karst geology that produces Florida's springs. Property owners in the region face insurance considerations that differ from other parts of the state, since sinkhole coverage is handled separately from standard perils.

Reclaimed mine lands have found second uses, including as parks, wildlife areas and residential development, and the county has worked to convert former industrial land into community assets.

The Piney Point precedent

Any discussion of phosphogypsum containment in Florida runs through Piney Point, a former phosphate processing plant in Manatee County that has become the state's cautionary example.

The facility was abandoned by its operator, leaving the state responsible for a stack system holding hundreds of millions of gallons of process water. When containment threatened to fail in 2021, emergency discharges released nutrient-laden water into Tampa Bay, a system already managing water quality pressures.

The discharge was followed by a severe red tide bloom along the Gulf coast, and while the causal relationship between the two has been debated among researchers, the sequence shaped public perception decisively.

Florida has since funded a closure project intended to permanently eliminate the site's containment risk, including deep well injection of treated water and consolidation of the remaining material.

The episode established two points that inform current debate. Abandoned facilities become public liabilities, and the financial assurance requirements imposed on operators determine whether taxpayers absorb closure costs. And containment failures in Florida's geology can move contamination into water bodies quickly, which raises the standard any beneficial-use proposal has to meet.

What's next

The Eleventh Circuit's decision resolves this challenge. The Center for Biological Diversity could seek rehearing before the panel or the full court, or petition the United States Supreme Court for review, though the Supreme Court accepts a small fraction of petitions.

The EPA retains regulatory authority over phosphogypsum and could revisit its approach through rulemaking, a process that would carry public notice and comment requirements.

The Florida Department of Environmental Protection regulates phosphogypsum stacks within the state, including construction standards, groundwater monitoring and closure requirements, and publishes compliance information on regulated facilities.

The test road's monitoring results, when they become available, will be the substantive evidence in any future debate about broader authorization.