1. News
  2. /
  3. Environment

Mosaic still can’t find source of polluted water seeping from gypsum stack

An environmental activist says the phosphate company should shut down its Bartow plant until it finds the source.
A giant sinkhole opened in 2016 at a Mosaic phosphate plant in Mulberry, Fixing it took two years and the secrecy surrounding the sinkhole damaged the company's public image. Now it's dealing with a mysterious seepage problem that it has not been able to figure out for three months. [JIM DAMASKE  |  Times]
A giant sinkhole opened in 2016 at a Mosaic phosphate plant in Mulberry, Fixing it took two years and the secrecy surrounding the sinkhole damaged the company's public image. Now it's dealing with a mysterious seepage problem that it has not been able to figure out for three months. [JIM DAMASKE | Times]
Published Dec. 19, 2019
Updated Dec. 19, 2019

Two months after discovering polluted water seeping from a phosphogypsum stack at its Bartow plant, Mosaic says it still doesn’t know where it’s coming from.

The phosphate company, though, says there is one piece of good news: “The seepage rate has now slowed from about 100 gallons a minute to 25,” company spokeswoman Jackie Barron said earlier this week.

The seepage was reported on Oct. 23 and appears to indicate a flaw of some sort in the plant’s phosphogypsum stack, a pile of radioactive waste material left over from processing phosphate rock that is turned into fertilizer.

About two dozen such gypsum stacks dot the Central Florida landscape, rising up to 200 feet high and often covering hundreds of acres.

At the top of each stack is a large pond of acidic water left by the factory process. That polluted water appears to be what is seeping out, but so far no one knows why or how.

RELATED: Polluted water seeping out at Mosaic plant.

To Dennis Mader of People for Protecting Peace River, the solution is simple: Mosaic “should stop their operation there and drain that pond and find out what’s going on.”

After all, he said, the stack where the seepage is occurring is “just an accumulation of toxic waste,” and that makes any structural problems a threat to the surrounding community.

But Barron says inspections by the company’s workers show that the seepage signals no change in the structure’s integrity. She said it “does not represent any threat to the environment and shows no off-site impacts.”

The polluted water “is being fully captured and contained onsite by a sump area and pump that was initially installed when the seepage was discovered ... The seepage remains contained onsite and does not pose a threat to water resources," Department of Environmental Protection spokesperson Dee Ann Miller said in an email to the Tampa Bay Times.

In 2016 a sinkhole opened beneath a Mosaic gypsum stack at its Mulberry plant, draining 215 million gallons of wastewater from a pond on the top of the stack into the aquifer beneath. Although the company notified state environmental officials, it did not disclose the problem to the public until a television station revealed it.

RELATED: As water disappeared down sinkhole, Mosaic avoided the s-word.

It took Mosaic two years to fill that hole.

Neither Mosaic nor state officials revealed the seepage problem in October, and defended that decision by pointing out that the problem has not affected anyone outside Mosaic’s property line.

“A team of experts is working seven days a week on tracking down the source in a strategic, methodical and safe approach” to find a solution, Barron said.

They have even tried pumping dye into the gypsum stack.

“So far it’s been inconclusive but we’re working section by section,” she said.

Further complicating the investigation: The Dec. 9 discovery of what Miller called “a surface settlement crack on the access road on the northwest corner of the south stack.” A report Mosaic filed with the state on Dec. 12 called it "a small surface indentation that may be indicative of a void” underneath the road.

A “void” would mean another potential sinkhole. But Barron said the company checked and found no such problem, and no sign that indentation is connected to the mysterious leak. She said the indentation is in the process of being repaired, and it should be done this week.

“To be clear, this reported surface settlement crack DID NOT result in release of process water in any way,” Miller said in her email. “Further, there are NO signs of any failure of the geology underlying the gyp stack system.”


  1. A slurry of dead fish, the result of Red Tide, moved out of Clearwater Harbor on the north side of Sand Key Park during a 16-month-long algae bloom. So many fish were killed that the state is limiting anglers to catch-and-release when it comes to snook, redfish and sea trout.  [Times photo (2018) by Douglas R. Clifford]
  2. A pair of wood storks, left, and a large group of white ibis rest and feed in a wetland area off Loop Road in the Big Cypress National Preserve. Florida is home to more wetlands than any other state except Alaska. [DOUGLAS R. CLIFFORD | Times (2008)]
  3. Pasco County commissioners introduced an ordinance Tuesday governing upkeep of empty property after residents complained about the condition of the Links Golf Club in Hudson, which closed in June 2019.
  4. Rep. Blaise Ingoglia on the floor of the Florida House in 2017. [SCOTT KEELER   |   Times]
  5. In this radar image from the National Weather Service's Key West facility, a massive flock of migratory birds is seen moving north early Monday. The green/yellow objects are biological objects flying north over the Keys. The darker blue objects indicate rain.
  6. These marine mammals were named "right whales" because they were considered by whalers to be "the right ones to hunt."
  7. Island Estates, a neighborhood in Clearwater Bay. There are three City Council races on this year's ballot as the city prepares for the realities of climate change.
  8. Florida Department of Environmental Protection staff conduct regular seagrass monitoring to assess the health and diversity of seagrass meadows within the St. Martins Marsh and Big Bend Seagrasses Aquatic Preserves north of Tampa Bay. A state legislator wants to extend the aquatic preserve to all of Citrus, Hernando and Pasco counties.

Charlie Shoemaker for The Pew Charitable Trusts
  9. One of two dolphins found dead in Florida recently of gunshot or stab wounds.
  10. Florida stopped providing free juice at welcome centers last year. [Times (2015)]
  11. USF scientist Stephen Hesterberg holds two oyster shells from Crystal River -- one small and modern, the other large and prehistoric. Hesterberg was part of a team of scientists who have documented how Florida oysters have shrunk since prehistoric times. Climate change may be a factor. [Courtesy of the University of South Florida]
  12. In this Jan. 29, 2020 photo made available by the U.S. Fish and Wildlife Service, confiscated hammerhead shark fins are displayed at the Port of Miami. The U.S. Fish and Wildlife Service said Monday, Feb. 3, 2020, that the shipment of dried fins was believed to have originated in South America and was likely bound for Asia. Officials estimate the total commercial value of 18 boxes of fins to be between $700,000 and $1 million. (U.S. Fish and Wildlife Service via AP)