Mosaic urged the 11th U.S. Circuit Court of Appeals to dismiss as “moot” a lawsuit filed by the Center for Biological Diversity challenging the project. The environmental group filed the lawsuit against the U.S. Environmental Protection Agency, which last year approved the use of phosphogypsum for the pilot project on Mosaic property.
“Mosaic began construction activities the week of August 25, 2025, and began applying phosphogypsum as road base on October 7, 2025,” the company, which intervened in the case on the side of the EPA, said in Friday’s filing.
“It completed all portions of the road that involved phosphogypsum on November 4, 2025. Although Mosaic is still working to complete some ‘control’ sections of the road, those sections do not use any phosphogypsum — they are constructed from common road materials. Mosaic and University of Florida scientists and engineers will also test and monitor the road base as described in the (EPA) approval.”
Mosaic attorneys added, “This action (lawsuit) is now moot because construction of the phosphogypsum portions of the pilot road project is complete. The court should accordingly dismiss the (Center for Biological Diversity) petition for review.”
The Center for Biological Diversity filed the challenge in February, about two months after the EPA approved the project at Mosaic’s New Wales facility. The issue of using phosphogypsum in road-building has long been controversial, as opponents have pointed to potential cancer risks from the substance, which is typically stored in huge stacks, known as “gypstacks.”
In challenging the project, the Center for Biological Diversity has contended, in part, that a 1992 federal rule bars using phosphogypsum in road projects. It has cited concerns about radon emissions and potential air and groundwater pollution.
The EPA said in a court filing this year that the project was limited to a 3,200-foot road. Mosaic — a major player in the phosphate industry — used phosphogypsum from a stack on the New Wales property for the project, according to a declaration of a company official attached to the company’s filing Friday.
Mosaic and the EPA have disputed the Center for Biological Diversity’s arguments in the case.
“At bottom, EPA approved a site-specific project presenting total risks that are at least an order of magnitude less than placement of phosphogypsum in a stack,” EPA attorneys wrote in a September brief.
Mosaic said in a separate September brief that the Center for Biological Diversity’s “real concern is that the pilot will serve as a gateway to broader beneficial use of phosphogypsum in road base.”
Phosphogypsum includes radium, which decays to form radon gas. Radium and radon can cause cancer, and the giant stacks are used to try to limit public exposure to radon emissions, according to information on the EPA’s website.
