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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.

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.”