Mosaic phosphogypsum road project upheld by U.S. court

Federal court upholds EPA approval of Mosaic’s Florida phosphogypsum road project

A federal appeals court has upheld the U.S. Environmental Protection Agency’s approval of Mosaic Fertilizer’s experimental use of phosphogypsum in a road at the company’s New Wales facility in Florida, resolving a legal challenge that had questioned both the EPA’s authority and its assessment of potential health risks.

On August 12, 2026, the U.S. Court of Appeals for the Eleventh Circuit denied a petition from the Center for Biological Diversity seeking to overturn the EPA’s approval. In its 48-page opinion, the court concluded that the EPA acted within its regulations and that its technical risk-assessment methodology was sufficiently supported and explained.

The decision allows the Mosaic pilot project to remain in place, but it does not establish a general authorization for phosphogypsum to be used in road construction across the United States. Any future project would still require separate EPA review and approval.

What the federal court decided

The case centered on the EPA’s December 2024 approval of a small-scale road project at Mosaic’s privately owned New Wales facility in Polk County, Florida.

The Center for Biological Diversity argued that the approval conflicted with federal regulations governing phosphogypsum and that the EPA’s risk assessment was arbitrary and insufficient. The organization also challenged several assumptions used by the agency to estimate exposure to workers, road users and nearby residents.

The Eleventh Circuit rejected those arguments.

The court emphasized that the dispute involved complex scientific and technical judgments. It found that the EPA had identified relevant exposure pathways, explained its assumptions and provided a coherent basis for its decision.

What Mosaic’s phosphogypsum road project includes

The EPA approved the New Wales project after concluding that the proposed use would be at least as protective of public health as keeping the phosphogypsum in an engineered stack.

The road is located on controlled private property at Mosaic’s fertilizer production complex and is intended as a research and demonstration project rather than a public highway.

Under the conditions imposed by the EPA, Mosaic must conduct environmental sampling, provide regular project updates and submit a final report evaluating the suitability of phosphogypsum as a road-base component.

The company must also sample the actual phosphogypsum used in the project for radium-226 before its removal from the stack and inform construction workers that the material contains elevated levels of naturally occurring radionuclides.

What is phosphogypsum?

Phosphogypsum is a solid byproduct generated during the production of phosphoric acid from phosphate ore. Phosphoric acid is a key raw material used to manufacture phosphate fertilizers such as MAP and DAP.

According to the EPA’s phosphogypsum guidance, phosphate ore and the resulting phosphogypsum contain naturally occurring radium. Radium can decay into radon, a radioactive gas, which is why U.S. regulations generally require phosphogypsum to be stored in engineered stacks.

Federal regulations permit only limited uses without special approval. Other uses, including road construction, require an individual application to the EPA.

For each application, the agency evaluates factors such as:

• the amount of phosphogypsum involved;
• radium concentrations;
• worker exposure;
• transportation exposure;
• exposure of road users and nearby residents;
• radon emissions;
• potential effects on surface water and groundwater.

Why environmental groups challenged the approval

The Center for Biological Diversity opposed the project during the EPA’s public review and later asked the federal appeals court to overturn the agency’s final decision.

The challenge focused partly on whether road construction could legally qualify as an approved “other use” under federal phosphogypsum regulations.

The organization also questioned the EPA’s risk assumptions, including the duration of potential exposure for construction workers, truck drivers, road users and nearby residents. It argued that some environmental pathways had not been adequately considered and challenged the age and quality of radium sampling data used during the review.

The court ultimately found that those objections were not enough to invalidate the EPA’s approval. It noted that EPA used conservative assumptions in portions of its radiological analysis and required new sampling of the material before construction.

EPA received more than 22,000 public comments

The New Wales project attracted substantial public attention before receiving final approval.

According to the EPA’s response to public comments, the agency identified 91 discrete comments during the review process. Several included electronic petitions, bringing the total number of comments and petition signatures to more than 22,000.

Most comments opposed the project or raised broader concerns about phosphogypsum management and the possibility that the pilot could encourage wider use of the material in roads.

The EPA responded that its approval was limited specifically to Mosaic’s private pilot project and did not provide a general authorization for public road construction.

Mosaic began construction in 2025

The project has progressed significantly since the original Fertilizer Daily report was published in February 2025.

A March 2026 project update submitted to the EPA shows that pre-construction sampling was completed during the summer of 2025 and road construction began on August 25, 2025.

Mosaic’s March 2026 update also identified two construction issues discovered during quality-control review.

• Some areas of the asphalt layer did not meet the intended thickness and were scheduled for adjustment to a minimum thickness of three inches.
• The road-base layer was installed at eight inches rather than the ten inches described in the EPA approval. Mosaic told the agency that the eight-inch base was consistent with Florida Department of Transportation guidelines and was not expected to compromise environmental monitoring or the road evaluation.

The company said a further quality-control assessment would be conducted after the repair work was completed.

Groundwater remains part of the monitoring program

Potential effects on groundwater were one of the environmental issues raised during the review.

The EPA assessed the possibility of radionuclides leaching into surface water or groundwater and concluded that the associated radiological risk for this specific project was low relative to direct exposure and radon inhalation risks.

However, the agency required Mosaic to conduct groundwater monitoring for at least 18 months after road construction.

The EPA also cautioned that data from the limited pilot should not automatically be used to support conclusions about long-term or full-scale road construction. The agency has repeatedly stated that any future phosphogypsum road proposal would require its own application and analysis.

The ruling does not approve phosphogypsum roads nationwide

The August 2026 court ruling is significant for Mosaic and the U.S. phosphate industry, but its scope is limited.

The ruling means that:

• EPA’s approval of the New Wales pilot remains valid;
• Mosaic can continue the approved monitoring and research program;
• the EPA can consider road construction under its case-by-case “other use” process;
• future road projects are not automatically approved;
• each future project would require a separate application, risk assessment and EPA decision.

The court specifically rejected the argument that approval of the Mosaic project itself creates a regulatory pathway automatically authorizing phosphogypsum roads elsewhere.

What happened to Mosaic’s separate Florida wastewater well proposal?

The original Fertilizer Daily article also discussed a separate Mosaic proposal involving underground wastewater management at its Plant City facility. That proposal should be distinguished from the New Wales phosphogypsum road project because the two involve different facilities, regulators and permitting processes.

The Florida Department of Environmental Protection considered a permit for a Class V exploratory well at Mosaic’s Plant City facility designed to reach approximately 8,000 feet below ground.

Importantly, the exploratory permit described by Florida DEP did not authorize routine underground disposal of fertilizer wastewater.

The exploratory well was intended to provide geological information about whether subsurface formations could potentially be suitable for future injection. Any actual underground injection of wastewater would require a separate permit and an additional regulatory review.

This distinction is important because concerns about road construction and underground wastewater injection relate to different methods of managing wastes generated by phosphate fertilizer production.

Why the case matters for the phosphate fertilizer industry

Florida is one of the most important phosphate-producing regions in the United States, and phosphogypsum management remains a major long-term challenge for fertilizer manufacturers.

Large quantities of phosphogypsum are generated when phosphate rock is converted into phosphoric acid. Most of the material is stored in stacks because alternative uses remain heavily regulated.

If pilot projects eventually demonstrate technically and environmentally acceptable uses for phosphogypsum, fertilizer producers could gain additional options for managing a major production byproduct. However, the current Mosaic project does not resolve the broader question of whether phosphogypsum can be widely reused in road construction.

The New Wales pilot is designed to produce additional information on:

• road performance;
• environmental leaching;
• groundwater conditions;
• radiological exposure;
• the technical suitability of phosphogypsum-containing road base.

Those results may inform future research or applications, but the EPA has stated that broader projects would still require independent review.

What happens next

With the legal challenge rejected, attention now shifts back to the environmental monitoring program at New Wales.

The project schedule submitted to the EPA extends into 2027, with recurring environmental sampling and status reports followed by a final project report.

The key issues to watch are:

1. results of groundwater and environmental monitoring;
2. performance of the phosphogypsum road sections compared with control sections;
3. whether monitoring identifies significant leaching or radiological issues;
4. Mosaic’s final conclusions on road-base performance;
5. whether Mosaic or other fertilizer producers later submit applications for additional phosphogypsum road projects.

The August 2026 court decision removes a major legal obstacle for the existing New Wales pilot, but it does not settle the wider debate over phosphogypsum reuse. For now, the project remains a closely controlled experiment involving a single private road at one Florida fertilizer facility.

Sources: EPA, U.S. Court of Appeals for the Eleventh Circuit, Florida DEP