In October, Tampa Fortune 500 mining company Mosaic warned Florida environmental regulators there may be another possible tear in the liner beneath a pile of the company’s mildly radioactive phosphate waste at its plant in Mulberry.
There was a change in the water pressure at Mosaic’s active south gypsum stack, the company told the state, which could mean an unknown amount of water from the manufacturing process may be released into the environment. The company said it would investigate the potential problem.
Now, state environmental regulators confirm that Mosaic’s investigation of the incident in December revealed there was, indeed, a liner tear beneath the northwest portion of the stack. The mining company has since been running exploratory drills to repair the tear, according to Florida Department of Environmental Protection spokesperson Brian Humphreys.
/cloudfront-us-east-1.images.arcpublishing.com/tbt/NYPROS2RWFEWPBN3BWBDB47HKE.PNG "This image, taken at Mosaic's New Wales facility and included in a state inspection report, shows workers using a device called a piezometer to measure underground pore pressure.")
Mosaic is also working to address a void, or “an underground open space,” that was detected beneath the pile of phosphogypsum, Humphreys said. The state didn’t immediately provide more details about what caused the void to form.
Jackie Barron, a spokesperson for Mosaic, wrote in an email that “we’ve done and continue to do significant stakeholder outreach as to any and all developments in our operations at New Wales.”
Mosaic informed both federal and state environmental regulators of the confirmed liner tear in a Dec. 14 letter. The company’s environmental director, Santino Provenzano, said a drilling crew confirmed the liner tear a day prior and was “advancing additional exploratory borings in this area to facilitate further evaluation.”
In a separate letter dated the same day, an environmental engineering firm hired by Mosaic recommended the company keep water out of the stack area. The firm also urged the continued investigation of the spot of the liner tear “to determine the extent and configuration of the cavity in gypsum at the base of the stack.”
This liner tear is the latest incident at the mining company’s plant in Polk County. In 2016, a sinkhole stretching 152 feet opened beneath the New Wales gypstack and resulted in 215 million gallons of contaminated water draining into the aquifer below.
Mosaic had been monitoring this section of the gypsum stack as part of a seismic monitoring system that was required by the state in 2021. Mosaic stopped adding more mining waste and process water storage there in 2022. In March of that year, Mosaic discovered a separate liner tear on the eastern portion of the stack and a resulting 300-foot “cavity,” according to a letter from the Florida Department of Environmental Protection.
/cloudfront-us-east-1.images.arcpublishing.com/tbt/UD4IDQTGHFFUZM43GMJ7RO2ZFE.JPG "Keep up with Tampa Bay’s top headlines")
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Explore all your optionsThis is the same facility where Mosaic wants to test its phosphate manufacturing waste as an ingredient in road building, according to documents filed to the U.S. Environmental Protection Agency. The company met with federal regulators as recently as November to discuss the proposal, records show.
Mosaic is required to continue fixing this latest liner tear, which includes accessing, grouting and repairing the liner seal at the base of the phosphogypsum stack. Rainfall and “process water” is usually stored in ponds on top of active gypsum stacks, but there’s no process water above the area of the liner tear, Humphreys said. The tear is in a part of the stack where a recovery well, acting almost like a giant straw, could capture and contain any releases and prevent it from polluting water underground.
The state’s environmental regulators are carrying out onsite inspections to oversee Mosaic’s response efforts, Humphreys said.
/cloudfront-us-east-1.images.arcpublishing.com/tbt/IMXTRNBVQNDS3PDRE3FRC3BD6I.PNG "This image was included in a Florida Department of Environmental Protection inspection report Oct. 21 and shows the part of Mosaic's phosphogypsum stack where a liner tear occurred.")
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