Residents question radioactive waste plans near historically Black Florida community

Riverview East Stack Extension at a glance

Imagine driving past what looks like a white mountain near Tampa, then learning it stores waste from fertilizer production. The official Riverview East Stack Extension would enlarge Mosaic Fertilizer’s active phosphogypsum stack beside the Riverview manufacturing plant in Hillsborough County.

The project has drawn attention because phosphogypsum contains radioactive material, while the nearby community includes homes, schools, parks, and long-established neighborhoods. Federal records show the proposal is still under environmental review, so the expansion is not a finished deal.

Why does the Riverview East Stack Extension matter?

The Riverview East Stack Extension involves phosphogypsum, a solid waste produced when phosphate rock is processed into phosphoric acid for fertilizer. EPA says phosphogypsum contains radium, which can decay into radon, a radioactive gas that can increase lung-cancer risk after prolonged exposure at elevated levels.

That does not mean nearby residents will develop cancer. EPA generally requires phosphogypsum to be managed in engineered stacks designed to limit public exposure to radionuclides, making proper storage, monitoring and long-term management important.

Riverview East Stack Extension near homes

The Riverview East Stack Extension is a $260 million proposal that would add storage space to Mosaic’s operating East Stack. Federal permit documents say the project footprint includes about 178.5 acres of new stack area and would let the Riverview plant keep operating for 16 more years.

If approvals are granted, construction is expected to start in January 2028 and take about two and a half years. Mosaic says the extra space is needed because the current East Stack is approaching its storage limit, while federal reviewers are still weighing environmental impacts, permits, and required mitigation measures before work begins.

Progress Village has a long history

Progress Village is more than a spot on a Tampa-area map. It was established in the late 1950s to provide affordable housing for Black families during an era of segregation and displacement linked to redevelopment in established African American neighborhoods.

The U.S. Census Bureau counted 11,188 residents in 2020, up from 5,392 in 2010, meaning the population more than doubled during that decade. The Census Bureau does not currently publish a 2025 population estimate for Progress Village CDP.

Why does the location raise questions?

The proposal is not in a remote part of Florida. A Progress Village planning project says Mosaic’s gypsum stack overlooks the Larry Sanders Sports Complex, while the Army Corps places the project review area less than one mile east of Hillsborough Bay.

Residents and environmental groups have raised questions about water quality, extreme rainfall, flooding, wetlands and long-term management. Mosaic’s proposal includes liners, a cutoff wall, water-collection systems and other controls intended to reduce environmental impacts.

What is phosphogypsum, really?

Phosphate rock naturally contains small amounts of radioactive elements. During wet-process fertilizer production, much of the radium becomes concentrated in phosphogypsum, the solid waste byproduct that is transported as a watery slurry and placed in large engineered stacks.

EPA says radium can decay into radioactive radon gas, which is one reason federal rules restrict how phosphogypsum is managed. Some U.S. stacks cover hundreds of acres and rise hundreds of feet, serving as long-term storage structures for the waste.

How is the waste regulated?

Phosphogypsum storage is subject to federal and state requirements. EPA’s Clean Air Act regulations require phosphogypsum to be managed in engineered stacks to limit public exposure to radionuclides, while inactive stacks are subject to radon monitoring and reporting requirements.

The Riverview expansion also requires Clean Water Act review because the proposed construction would affect aquatic resources. The Army Corps says Mosaic is seeking authorization to place about 305,000 cubic yards of clean fill into roughly 35.2 acres of aquatic resources.

Hurricane Milton tested the site

Florida weather adds another layer to the discussion because heavy rain can put pressure on industrial water systems. After Hurricane Milton in 2024, Mosaic said nearly 15 inches of rain overwhelmed a water-collection system associated with its closed Riverview phosphogypsum stack, allowing impacted stormwater to reach an outfall connected to Tampa Bay.

Reuters reported that the discharge may have exceeded the 17,500-gallon reporting threshold, although Mosaic did not provide a total volume. The company said any effect on bay water quality was expected to be modest, making the incident relevant to future reviews of storm capacity and emergency planning.

Little-known fact: During Hurricane Milton in 2024, AP reported that environmental groups and officials watched several phosphate waste sites closely because extreme rainfall can challenge large industrial water systems.

Storm concerns have a history

Concerns about storms did not begin with Hurricane Milton. NOAA records show that Hurricane Frances in September 2004 caused the release of an estimated 65 million gallons of acidic process water from Mosaic’s Riverview facility into Archie Creek Canal, Hillsborough Bay and surrounding wetlands.

Past incidents do not prove that the proposed expansion will fail, but they provide real events for regulators to consider when reviewing rainfall capacity, drainage, containment and emergency planning.

Little-known fact: Florida has multiple phosphogypsum stacks connected to its phosphate fertilizer industry.

How does the federal review work?

The Riverview proposal is moving through FAST-41, a federal process created to coordinate reviews and set permitting schedules for major projects. The Riverview East Stack Extension became the first manufacturing project covered by FAST-41, and the U.S. Army Corps of Engineers is listed as the lead federal agency.

The federal permitting dashboard currently shows the environmental review and permitting process as still in progress, with a completion date in March 2027. A faster, coordinated schedule does not remove legal requirements, but critics want careful review.

Why does Mosaic say the plant matters?

Mosaic argues that the Riverview plant matters beyond Hillsborough County because phosphate fertilizer supports farms and food production. The company says it is the country’s largest domestic supplier of phosphate crop nutrients.

Mosaic also says the project would use disturbed land where possible and include systems meant to control seepage. Company materials describe conservation commitments nearby as part of the plan, but those promises still sit alongside regulatory review, environmental concerns, and public questions.

A community with mixed views

Progress Village residents do not all view Mosaic in the same way. Some have raised concerns about the stack and its possible effects, while others point to the company’s jobs, donations, scholarships, youth support, and other ties to the community.

Inside Climate News reported that Mosaic also agreed to air monitors at Progress Village Middle Magnet School and nearby Gibsonton Elementary School. That mix of concerns and connections makes the debate more complicated than a simple fight between two sides.

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What happens next?

For now, the Riverview East Stack Extension remains under review. Federal records show that several permitting and environmental-review steps remain unfinished, and required agency decisions must occur before the proposed expansion can proceed.

If the necessary approvals are granted, the Army Corps’ current project description says construction is expected to begin in January 2028 and take approximately two and a half years. The proposal is currently being scrutinized by regulators, Mosaic, environmental organizations and members of the surrounding community.

Curious how a flyer review turned into a national discussion? Learn more about the Florida A&M University situation and the response that followed.

What do you think about the proposed Florida waste stack expansion? Share your thoughts in the comments.

This slideshow was made with AI assistance and human editing.

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