Polluted water is seeping at Mosaic site

The Florida Department of Environmental Protection launched an investigation last month into a “seepage” problem at one of phosphate giant Mosaic’s massive phosphogypsum stacks.

But neither the company nor the agency alerted the public about the problem.

State investigators showed up at Mosaic’s Bartow plant on Oct. 23, the day the problem was reported by Mosaic, agency spokeswoman Dee Ann Miller said Tuesday. They have returned the plant three more times so far, she said.

“At this time, inspections and data submitted indicate that the seepage is contained onsite and has not impacted water resources,” Miller said in an email to the Times. “There are NO signs of any failure of the geology underlying the gyp stack system.”

The stacks are piles of slightly radioactive waste material left over from processing the phosphate for fertilizer. They rise up to 200 feet high and often cover hundreds of acres. On top of each one is a large pond of acidic water.

A Mosaic spokeswoman, Jackie Barron, echoed that statement Tuesday. “The gyp stack structure itself remains structurally unaffected by the seepage outbreak at this time.”

This investigation comes three years after a sinkhole opened beneath a Mosaic gyp stack at its Mulberry plant, draining 215 million gallons of wastewater from a pond on the top of the stack into the aquifer beneath. Filling that hole took Mosaic two years.

PRIOR COVERAGE: As polluted water disappeared, Mosaic avoided using “s-word.”

The public was not notified about the 2016 sinkhole by either the company or the agency until, three weeks later, a television report exposed the problem. Then-Gov. Rick Scott said that was wrong, and persuaded legislators to change the law to require prompt public reporting of such pollution incidents.

PRIOR COVERAGE: After three-week delay, Gov. Scott calls for faster notice.

To environmental groups, this incident at the Bartow plant is a repeat of the 2016 event, which occurred 15 miles away at a plant on the Hillsborough-Polk county line.

“Once again, Mosaic and the FDEP kept this breach under wraps for more than three weeks despite requirements that such events must be reported immediately, imposed by the former governor,” environmental activist Dennis Mader of People for Protecting Peace River wrote in an email.

But Miller said this incident did not meet the law’s requirements for public notice because the water flow didn’t get far enough.

“The owner or operator would be required to submit a notice if a release impacted waters of the state or migrated offsite," she explained. Instead, she said, this flow has been contained above ground within the area of the gyp stack.

And Barron emphasized that the seepage is occurring above-ground, not into the aquifer.

The discovery of the seeping water happened during a routine inspection, company officials said. On Oct. 23, a field inspector driving the area noted water seeping out from the southwest corner of the active gyp stack. The flow of water continued to a nearby on-site swale, they said.

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The company scrambled to contain the flowing water, according to the report Mosaic filed with the state on the first day. Workers installed a pump to collect what had seeped out and return it to the stack’s water management system. They also built an earthen dam to prevent it from migrating off the company’s site.

A possible source of the water is the 55-acre pond atop the stack, which Barron said holds about 164 million gallons of polluted water. But Barron said the company is still trying to determine the source. A nearby holding pond is another possibility, she said.

She and Miller both said the investigation is focusing on the possibility that the high density polyethylene lining that’s supposed to contain the ponded wastewater has torn. The stack was originally built before state law required a lining, but one was added a decade ago and a new stack built atop that one, Barron said.

Barron emphasized that the term for what’s happening is “seepage,” not “leak.”

“Seepage meaning the water is moving through a porous surface versus leaking out some kind of opening,” she said.

Senior news researcher Caryn Baird contributed.