The incident happened at Mosaic's New Wales phosphate mine, along the Polk-Hillsborough county line. State regulators say their data showed a change in water pressure at one of the mine's gypsum stacks. The stacks contain a mix of rain and wastewater from the production of fertilizer.
If a tear is discovered, regulators say the phosphate waste could be recovered on site before seeping into the underground aquifer.
That's of little comfort to environmental groups opposed to expansion of phosphate mining. Ragan Whitlock is with the Center for Biological Diversity.
"We have a water loss incident where process wastewater was released. And there really is no other apparent source of that, other than a liner tear," he said.
Mosaic spokeswoman Jackie Barron says they are investigating the incident. But heavy equipment has to be moved in place at the mine, and it could be next week before engineers can confirm if there is a tear.
Several sinkholes have previously been reported at the New Wales mine, including one in 2016 that dumped hundreds of millions of gallons of polluted water into the aquifer. And Mosaic has applied for state permits to expand the mine. It took more than two years to seal the opening.
"This is a site that the industry looks at as being a recipient of phosphogypsum and process wastewater for its expanded mining operations in southwest Florida," Whitlock said. "And this facility has shown that it cannot handle that additional workload."
