Mosaic will permanently close its long-idled Plant City fertilizer plant

PLANT CITY — Mosaic announced Tuesday that it will permanently close its Plant City fertilizer plant, which has been idled since 2017 because of slowing demand for phosphate.

However, some employees will have to remain on site to help decommission one of the plant's phosphogypsum stacks, a process company officials expect to take several years. To get rid of the water on top of it, the company has been transferring some of it to other facilities every day since 2017, according to spokeswoman Jackie Barron.

Such gypsum stacks, built with slightly radioactive material from phosphate processing, loom over the Florida landscape, with a pool of acidic water on top. In 2016, a sinkhole opened beneath a Mosaic gypsum stack in Mulberry, draining the pool on top into the aquifer and setting off a major public health scare and public relations problem for the company.

The Plant City plant has two of the stacks, but the first closed in 2004. Started in 1965 on State Road 39 just south of the Hillsborough-Pasco county line, the facility once employed 430 people. It could produce 2 million tons of fertilizer a year from the material dug up in the mines of Central Florida. In its last year, it cranked out only 1.3 million tons.

The plant operated at a higher cost than other Mosaic facilities in Florida, and when the global demand for fertilizer began dropping, the company chose to relocate many of its employees and shut it down temporarily.

More than 200 employees were offered new spots and 131 opted for early retirement while another 98 took severance packages, Barron said. Now the plant will be closed permanently.

"Our decision to close the Plant City phosphate facility reaffirms our commitment to low-cost operation," Mosaic president and CEO Joc O'Rourke said in a news release sent out by the company.

During the second quarter, Mosaic expects to recognize a notable non-cash charge of up to $390 million for the permanent closure of the facility, including asset write-offs and an increase of the asset retirement obligation liability. Annual cash payments to manage the closure of the facility over the next five years are expected to be similar to payments incurred while the plant was idle in 2018.

The company news release mentions the possibility of "repurposing part of the facility for productive use," but offers no details about what that might mean.

Mosaic has been working hard to shift its Florida operations southward. Last year, DeSoto County commissioners voted 4-1 to deny the company a zoning change on 18,000 acres that would allow it to open a new mine there. But earlier this year the commissioners voted unanimously to void that vote and let Mosaic come back and try again in four years.

The Plant City plant was one Florida facility not targeted by the U.S. Environmental Protection Agency for mishandling hazardous waste. In 2015 Mosaic settled with the EPA for improper storage and disposal of waste from the production of phosphoric and sulfuric acids, key components of fertilizers, at Mosaic's facilities in Bartow, New Wales, Mulberry, Riverview, South Pierce and Green Bay in Florida, as well as two sites in Louisiana.

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The EPA said it had discovered Mosaic employees were mixing highly corrosive substances from its fertilizer operations with the solid waste and wastewater from mineral processing, in violation of federal and state hazardous waste laws.

Contact Craig Pittman at craig@tampabay.com. Follow @craigtimes.