Rejecting arguments of environmental groups, a divided federal appeals court has backed a decision by the U.S. Army Corps of Engineers to issue a permit sought by the phosphate company Mosaic for expanded mining operations in Florida.

A three-judge panel of the U.S. Court of Appeals for the 11th Circuit on Monday upheld a decision by the Army Corps to issue a permit needed by Mosaic to discharge dredged and fill materials into waterways.

Environmental groups challenged the permit, at least in part, because the Army Corps didn't take into account environmental effects of Mosaic producing and storing phosphogypsum, a radioactive byproduct of the manufacturing process of turning phosphate into fertilizer.

But the panel majority said the Army Corps was not required to consider phosphogypsum in determining whether to issue the discharge permit tied to mining.

"Phosphogypsum-related effects are, at most, tenuously caused by the discharge of dredged and fill material allowed by the Corps' permit," said the 37-page majority opinion, written by Judge John Rogers and joined by Chief Judge Ed Carnes. "Phosphogypsum is a byproduct not of dredging and filling — nor even of phosphate mining or beneficiation — but of fertilizer production. Further, the fertilizer production takes place far from and long after the Corps-permitted discharges."

But Judge Beverly Martin, in a 20-page dissent, wrote that a phosphate-rich region known as Bone Valley includes massive piles of phosphogypsum, describing it as "a monument to the lasting environmental impact of Florida's phosphate fertilizer industry." She wrote that phosphogypsum-tainted water has spilled into waterways and said the Army Corps should have considered the environmental impact of the phosphogypsum "stacks" before issuing the permit.

"This record shows that radioactive phosphogypsum stacks tower above Florida water sources, and these stacks have spilled waste into the surrounding waters," Martin wrote. "Production of more phosphogypsum is a clearly foreseeable result of Mosaic's phosphate mining and fertilizer operation. The Corps should have assessed the environmental impact that leaky phosphogypsum stacks might have on U.S. waters and the environment at large before granting Mosaic its permit."

The majority opinion said the issue is rooted in four proposed permits sought in 2010 and 2011 under the federal Clean Water Act. The Army Corps carried out a required environmental-impact study for the projects.

In 2016, it issued a permit for what is known as the South Pasture Extension, which is in Hardee County, according to Mosaic's website.

The permit was challenged by the Center for Biodiversity, ManaSota-88, Inc., People for Protecting Peace River, Inc., and Suncoast Waterkeeper.

But Monday's majority opinion said the Army Corps, in considering discharge permits, is not responsible for broader regulation of phosphogypsum.

"No federal law empowers the Corps to protect the environment writ large or to regulate phosphate mining as such, much less fertilizer production or phosphogypsum stacking," the opinion said. "Whatever federal regulatory powers there are over phosphogypsum-related effects, Congress granted to the EPA [Environmental Protection Agency], leaving the bulk of control over phosphate mining and fertilizer production to the states. Requiring the Corps to enter those regulatory spheres not only offends congressional design but risks duplicative, incongruous, and unwise regulation. Because the Corps does not generally regulate phosphogypsum, it has no subject-matter expertise in that area."

Martin, however, wrote that the "Corps did not do its job when it failed to consider phosphogypsum as an indirect environmental effect of Mosaic's … permit."

Jim Saunders reports for the News Service of Florida.