A phosphogypsum stack rising hundreds of feet behind a recreation center, sports complex, and middle school in Progress Village is about to get bigger. Mosaic Co., the nation's largest phosphate manufacturer, wants to expand the radioactive waste pile at its Riverview manufacturing site, and residents of the historically Black community next door say they are being asked to live even closer to a hazard that has already leaked toxic wastewater into Tampa Bay.
The Riverview site sits less than a mile from Hillsborough Bay and includes two phosphogypsum stacks alongside the manufacturing plant, according to Orlando Sentinel. One of those stacks is closed, but the active stack has about six more years of remaining storage capacity, and Mosaic is now seeking a Clean Water Act permit from the U.S. Army Corps of Engineers to keep it running far longer. In that permit application, Mosaic requested authorization to fill roughly 35 acres of wetlands, ponds, and ditches using about 305,000 cubic yards of material — enough to fill 100 Olympic-sized swimming pools — to expand the stack westward toward U.S. Highway 41, according to the Tampa Bay Times.
Mosaic estimates the expansion would cost $260 million and take about two-and-a-half years to complete, with construction projected to begin in January 2028. The project would extend the Riverview plant's operational life by about 16 years, and the company has said it would be built primarily on already disturbed land, with a dike and ditch system meant to prevent seepage.
A Community Built From Displacement, Now Facing Expansion
Progress Village, located southeast of Tampa, was established in the late 1950s to provide affordable housing for segregated Black residents displaced by Interstate 75 construction. Today the neighborhood is home to at least 11,000 people, per figures covering the past 16 years. Hillsborough County commissioners first approved construction of the Progress Village gypstack in 1984, and the stack was expanded about a decade later, in 1994.
Sean Bell Sr. characterized the current expansion push as environmental racism, according to the Orlando Sentinel's reporting. That framing echoes a broader pattern cited in litigation: African Americans are 75 percent more likely to live in a community next to an industrial site, per claims in a 2025 lawsuit referenced in the Sentinel's coverage. Marlise Tolbert-Jones, another resident quoted in that reporting, said simply that Progress Village is her home.
Phosphogypsum, the waste product of turning phosphate ore into fertilizer, contains radium, which decays into radon gas. Both radium and radon can cause cancer, and radon exposure specifically is the second-leading cause of lung cancer. Federal regulations under 40 CFR Part 61 (Subpart R) of the Clean Air Act, mandated in 1989 and 1992, require phosphogypsum from wet acid phosphorus production to be placed in engineered stack systems specifically to restrict public radiation exposure, according to the Federal Register.
Federal Fast-Tracking Meets Local Flood Risk
The expansion is moving through an accelerated federal approval process. In July 2025, the Federal Permitting Improvement Steering Council designated the $260 million Riverview East Stack Extension as the first-ever manufacturing project to receive federal FAST-41 coverage, a streamlined multi-agency review framework, per the Federal Permitting Improvement Steering Council. The designation followed a Trump administration executive order in 2025 calling for accelerated domestic critical mineral production, and phosphate's status as a critical mineral for agricultural fertilizer supply chains.
Ragan Whitlock has said he worries the expedited review could be less thorough, per the Sentinel's reporting. That concern is compounded by the region's flood exposure: Hurricanes Helene and Milton made landfall in Florida within 13 days of one another in 2024, causing wind and flood damage across Progress Village that reached two or three feet of water in places. Hillsborough County has since invested $18 million toward flood infrastructure projects in response.
The Hillsborough County Commission has voted to support the Riverview stack expansion, even as the site's own history includes wastewater releases. The Riverview facility released 65 million gallons of process wastewater into Tampa Bay after Hurricane Frances in 2004, and more recently released at least 39,600 gallons of toxic, acidic, nutrient-laden process wastewater into the bay in 2024, according to litigation cited by the Sentinel.
A Track Record of Spills Looms Over the Region
Florida's phosphogypsum stacks collectively store more than 1 billion tons of waste, and the industry adds roughly 40 million tons more each year. Individual stacks can rise hundreds of feet and span more than one square mile. The region's history with these piles is marked by disaster: in December 1997, a dam breach at the nearby Mulberry Phosphates fertilizer plant released 56 million gallons of acidic process water into the Alafia River, killing all aquatic life along a 42-mile stretch down to Tampa Bay and forcing that company into bankruptcy, according to WUSF.
More recently, the 2021 Piney Point disaster forced the evacuation of more than 300 homes after a pond threatened to collapse, ultimately releasing 215 million gallons of process wastewater into Tampa Bay, including about 200 tons of nitrogen. That release killed more than 1,600 tons of marine life and led to one of Tampa Bay's worst red-tide outbreaks in 50 years, per the Sentinel's account.
Mosaic's own New Wales facility in Mulberry has experienced at least five sinkholes, including one in 2016 that released about 215 million gallons of process wastewater and an undisclosed amount of phosphogypsum solids into the Floridan aquifer. That plant also experienced a liner tear in June 2023 and another liner tear in October 2023 that caused an unknown quantity of process wastewater to be lost. In October 2015, Mosaic Fertilizer LLC reached a $2 billion settlement with the EPA and U.S. Department of Justice over hazardous waste violations across eight facilities in Florida and Louisiana, agreeing to create a $630 million trust fund to finance future gypstack closures, according to the U.S. Department of Justice.
Roads Made of Radioactive Waste Face Their Own Legal Fight
Beyond stack storage, Florida has also pursued using phosphogypsum as a road-building material. In June 2023, Governor Ron DeSantis signed House Bill 1191 into law, directing the Florida Department of Transportation to evaluate phosphogypsum as an aggregate for road construction, a move tied to Florida's roughly 80 percent share of total U.S. phosphate production capacity. In December 2024, the EPA approved a pilot project allowing Mosaic to build a one-mile road using phosphogypsum at its New Wales plant in Polk County — a decision environmental groups challenged before the 11th U.S. Circuit Court of Appeals in April 2026, arguing the road construction exposes workers and the public to unacceptable cancer risks, according to Courthouse News Service.
Mosaic, which opened the Riverview facility in 1924, says the plant processes phosphate ore supplying roughly 18% of the phosphate fertilizer used in North America and generated $800 million in wages in Hillsborough County in 2025. The company has agreed to install air monitors at Progress Village Middle Magnet School and Gibsonton Elementary School, and has pointed to its record of hiring Progress Village residents, funding academic scholarships, sponsoring youth programs, and making large local donations. Hillsborough County Commissioner Gwen Myers has said Mosaic has continued to give back to the community.
Mosaic's community investments have played out in visible ways near the gypstack itself. In November 2025, Hillsborough County broke ground on Fire Station No. 48 to serve South Progress Village, made possible through a land exchange with Mosaic Fertilizer. And in December 2024, the county opened a $1 million aquatic splash pad at the Emanuel P. Johnson Recreation Center — a hub for youth programs situated adjacent to Progress Village's industrial border, not far from the stack itself.
Mosaic plans to expand the Riverview phosphogypsum stack again once the current proposal moves forward, according to the Sentinel's reporting. For now, the permit remains under federal review, and residents like Bell and Tolbert-Jones are left watching a stack that already looms over their neighborhood grow taller still.
