Mosaic Fertilizer has reached a $2 billion settlement with state and federal environmental regulators and the U.S. Department of Justice over funding for the long-term disposal of massive phosphogypsum waste piles and the treatment of 60 billion pounds of wastewater from its plants in Florida and St. James Parish, authorities and the company said Thursday.

The settlement would conclude a 10-year regulatory dispute in which the U.S. Environmental Protection Agency claimed Mosaic violated the federal Resource Conservation and Recovery Act and state hazardous waste laws.

Processes used to make phosphate fertilizer result in acidic wastewater and lots of phosphogypsum, an unwanted byproduct with trace radioactivity.

“This case is a major victory for clean water, public health and communities across Florida and Louisiana,” said Cynthia Giles, assistant administrator for EPA’s Office of Enforcement and Compliance Assurance, in an EPA statement Thursday.

The deal is subject to a 45-day public comment period in Louisiana and a 30-day public comment period in Florida and needs approval from federal courts in New Orleans and Florida, EPA officials said.

Mosaic officials said Thursday they will spend $170 million at their plants to modify how process wastewater is handled so it’s kept out of phosphogypsum stacks.

Mosaic has also agreed to set up a $630 million trust fund into which the company will invest until the fund reaches $1.8 billion. That money will pay for future closure of and long-term care for phosphogypsum waste stacks at the Bartow, New Wales and Riverview plants in Florida and the Uncle Sam plant in St. James Parish near Convent.

The money also will go toward long-term care for three more plant stacks already being closed, including one at Mosaic’s Faustina plant on the west bank of St. James, officials said.

Of the $8 million penalties, Mosaic will pay $5 million to the federal government, $1.55 million to the state of Louisiana and $1.45 million to the state of Florida.

Mosaic officials said Thursday the settlement won’t “adversely” affect production rates and doesn’t signal the imminent closure of any of their plants.

“We are pleased to be bringing this matter to a close,” Joc O’Rourke, president and CEO of Mosaic of Plymouth, Minnesota, said in a company statement.

Fertilizer companies, like Mosaic, mine phosphate rock and send it to processing plants where sulfuric acid is used to extract phosphorous for fertilizer used on corn, wheat and other crops. Most of Mosaic’s phosphate mines and plants are in Florida, but two plants are in St. James Parish.

Phosphogypsum, which is a solid waste, is difficult to reuse under current EPA rules due to its radioactivity and can present a risk to ground and surface water if the material is not properly contained.

In addition to ponds, tanks and ditches, the white waste material has been stored for decades in stacks up to 500 feet high and spread across 600 acres in Louisiana, Florida and elsewhere. The EPA said the stacks are some of the largest man-made waste piles in the U.S.

A white phosphogypsum stack for Mosaic’s Uncle Sam plant is visible off La. 3125 near Convent and stands 187 feet tall, Mosaic officials said.

Phosphogypsum is exempt from hazardous waste regulations, but EPA said inspections revealed Mosaic was mixing highly corrosive process water from its fertilizer operations with other waters and the phosphogypsum. The EPA claimed the corrosive wastewater had been used to clean equipment and air pollution scrubbers and in the production of sulfuric acid and other products.

EPA considered that water hazardous waste and so mixing it was deemed a violation of federal and state hazardous waste laws. Mosaic disputed that regulatory interpretation and admitted no fault in the settlement.

Debra Waters, Mosaic director of environmental regulatory affairs, said Thursday the company will continue to reuse the process water but is developing methods to keep it separate from the stacks. The water is now held in ponds on the stacks and in voids inside the stacks.

Under the settlement, Mosaic also will do two environmental projects worth $2.2 million in Florida and Louisiana.

Follow David J. Mitchell on Twitter @NewsieDave.