Worried about Piney Point? Polk County is ground zero for phosphogypsum stacks

The breach of a reservoir in Manatee County holding wastewater from fertilizer processing offers a reminder that Polk County contains plenty of similar sites.

The leak at the Piney Point phosphogypsum stack is threatening to release millions of gallons of contaminated water into Tampa Bay. The potential environmental catastrophe has drawn national attention.

At least a dozen such stacks exist in Polk County, according to the Florida Department of Environmental Protection. Those include the largest storage facility in the state, the 1,147-acre New Wales Stack, about five miles southwest of Mulberry.

Phosphogypsum is a byproduct of fertilizer production. In Florida, phosphate ore mined from the soil is treated to create phosphoric acid, a main component of fertilizer, and the process also yields phosphogypsum as waste.

That waste is stored in phosphogypsum stacks, often called gypstacks. The phosphogypsum is contained in reservoirs inside the structures, which can be hundreds of feet tall and cover hundreds of acres.

The process of removing phosphorous from mined rock leaves behind most of the naturally occurring radioactive material in the waste, according to an explanation from the Environmental Protection Agency. That concentration makes phosphogypsum more radioactive than the original phosphate rock.

For that reason, the material cannot be released and is stored permanently in gypstacks. The structures hold ponds that usually contain “process water” left over from fertilizer production. In addition to having increased radiation levels, the water is acidic and contains nutrients such as nitrogen and phosphorous.