The Tampa-based mining company Mosaic is looking to widen its phosphate waste pile in Hillsborough County in a sweeping expansion that would keep the facility open for another two decades, according to a federal notice and a proposal the company presented earlier this year.
The extension could stretch the towering mound of phosphogypsum, a mildly radioactive byproduct of the company’s fertilizer production, farther west toward U.S. Highway 41 and closer to the shores of Tampa Bay.
The plan, still in its early stages, would increase the gypsum stack’s total footprint by roughly 140 acres and make room for an estimated 48 million tons of gypsum storage, according to an initial estimate Mosaic gave in a company presentation earlier this year.
County, state and federal regulators who spoke with the Tampa Bay Times in recent weeks said Mosaic is in the initial phases of permitting, with an application to state oversight officials anticipated by mid-December.
The company has said it needs more storage for its phosphogypsum, a solid waste that contains radium, which decays to form radon gas. Because both radium and radon are radioactive and can cause cancer, federal regulators require that phosphogypsum be stored in engineered stacks, like the one in Riverview, to reduce the public’s exposure.
State data shows Mosaic owns and operates two-thirds of Florida’s 25 active and closed “gypstacks,” with most of those located in the phosphate-rich Bone Valley region east of Tampa.
Due to their size — stacks can be hundreds of feet tall — and the heavy industrial activity they require, Mosaic faces a potpourri of permitting, land-use changes and bureaucracy ahead.
For example: In a July federal notice, the Fortune 500 company said it is seeking permission from the U.S. Army Corps of Engineers to change an existing federal Clean Water Act permit to fill in approximately 16 acres of federal waters, including wetlands and other water bodies. The Corps said in a statement that a review is ongoing to determine which waters fall under federal authority.
In an emailed statement Oct. 22, the company said it continues to work through permitting at each level of government but does not have definitive dates for when it will apply for permits.
“Mosaic has a long history of engagement across our operational area,” spokesperson Chloe Conboy Renard wrote. “Our culture is to be active and involved where our employees work, live, and raise their families.”
The expansion will be the first manufacturing project that qualifies for an Obama-era federal program, called FAST-41, designed to streamline the complex permitting process for large-scale infrastructure projects. In a July news release, the council overseeing that coordination estimated the expansion’s price tag at $260 million.
“Ensuring that our farmers have a reliable fertilizer supply chain is essential for feeding Americans and the rest of the world,” Emily Domenech, executive director of the federal permitting council, wrote in the release. “I am confident that the accountability of our process will speed the federal permitting of this project.”
While no federal permits have been issued yet, the company in recent months has bought land on the west side of its nearly 370-acre active gypsum stack.
Since December, Mosaic has purchased more than 30 acres of nearby properties for at least $7.7 million, according to a review of Hillsborough County property records. That includes the former East Bay Raceway park and a vehicle storage lot the company acquired in October, property records show.
Progress Village Civic Council president Twanda Bradley said Mosaic brought up the expansion during a tour of the Riverview plant earlier this year. The proposal would expand the side of the gypstack that’s opposite to the community she represents. Bradley said the company has kept her apprised of updates from the plant, including a fire there last year, and she would like to see that communication continue.
The phosphate company said in its presentation that it will eventually host community workshops as the expansion process moves forward. “I’m hopeful they will keep bringing us to the table and keeping us in the loop,” Bradley said.
The prospect of shifting a sweeping industrial site closer to Tampa Bay’s shoreline has already raised concerns among some environmental advocates who worry about the region’s vulnerability to hurricane-fueled storm surge.
“It’s clearly risky to expand where Mosaic stores toxic pollution closer to Tampa Bay,” said Susan Glickman, vice president of policy and partnerships for The CLEO Institute, a climate education nonprofit. She cited a 2015 report listing Tampa as the most vulnerable city in the nation to storm surge.
“Why would we further endanger people by adding toxic pollution to those in harm’s way?” Glickman asked.
There’s at least one recent example of how a storm affected Mosaic’s Riverview facility: Last year, Hurricane Milton’s deluge of rainfall caused a water collection system to breach, spilling polluted water into Tampa Bay.
Several acres of wetlands are listed in the new project area, including Archie Creek, that could be altered by the expansion, according to a Mosaic application to county regulators. But it’s not yet clear how many acres of wetlands would be affected until the company submits a wetland impact and mitigation application, according to the county’s environmental protection commission.
To make up for the likely environmental impacts, Mosaic said it’s proposing stronger protections for a pair of islands it owns offshore the mouth of the Alafia River, known as the Richard T. Paul Alafia Bank bird sanctuary. Mosaic said it’s working with the county to designate the islands for natural preservation. The company said it’s also working on identifying areas to mitigate the possible impact to wetlands.
Before the company can move forward with expansion, it must receive approval from several governmental agencies at the local, state and federal levels, according to a February presentation by Brad De Neve, a former Mosaic engineer who now works as a land development engineer in Polk County, according to his LinkedIn profile. That includes Hillsborough County’s Environmental Protection Commission, the state’s environmental regulatory department and the Army Corps of Engineers.
De Neve said during that presentation that if all permits are approved, construction would begin in 2028, and the expanded gypstack would be operational about two years later.
The Riverview facility produces roughly 6,000 tons of fertilizer daily, according to company estimates.
While Mosaic looks to increase storage and alternative ways to use its phosphogypsum byproduct, the U.S. Environmental Protection Agency last year gave the company approval for a controversial project to begin testing it as an ingredient in road construction. Work on that pilot project using 1,200 tons of the byproduct is currently underway at Mosaic’s Mulberry facility.
This story was originally published by the Tampa Bay Times and shared in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the Sun-Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.
