A leak at an old phosphate plant site has threatened Tampa Bay for the last week with environmental catastrophe. Here we break down the pieces involved.
What is Piney Point?
It used to be a fertilizer manufacturing facility. Industrial byproducts of that process are still stored on site. That includes polluted water and phosphogypsum, a substance kept in stacks and monitored for its radioactivity. Managing those materials is expensive and hasn’t always gone well at Piney Point. Past discharges have hit the valuable waters of Bishop Harbor. Excess nutrients from wastewater can feed harmful algal blooms, which lead to fish kills.
What’s a phosphogypsum stack?
Drive through Central Florida and you might see one. They rise like large, flat-topped hills above an otherwise level state.
Phosphogypsum is a leftover from processing phosphate, which is part of making fertilizer.
The Environmental Protection Agency has a webpage all about it, noting that “phosphate rock mining is the fifth-largest mining industry in the United States in terms of the amount of material mined.”
It’s big business in Florida, a hub for fertilizer production. One of Tampa’s biggest companies is Mosaic, a miner.
Phosphate rock, according to federal regulators, contains phosphorus and also uranium and radium. The phosphorus is what fertilizer manufacturers want. They dissolve the rock “in an acidic solution” and that leaves phosphogypsum. Think of a slurry that dries out, creating what the government refers to as “a crust, which blocks most of the radon.”
“Most of the naturally-occurring uranium, thorium and radium found in phosphate rock ends up in this waste,” the Environmental Protection Agency says. “Uranium and thorium decay to radium and radium decays to radon, a radioactive gas. Because the wastes are concentrated, phosphogypsum is more radioactive than the original phosphate rock.”
Where does water come in?
Ponds of wastewater are sometimes stored atop phosphogypsum stacks. They may hold rainwater, as well as what’s known as process water — left by fertilizer production. Process water is acidic and carries nutrients like nitrogen and phosphorus. The Florida Industrial and Phosphate Research Institute explains that if a plant shuts down, that water has to “be treated before it can discharged.” In 1997, a wastewater overflow at Piney Point’s sister plant in Polk County sparked a devastating fish kill in the Alafia River.
So what is being discharged into Tampa Bay from Piney Point?
It’s a mix of seawater from an old dredging project that Piney Point’s operator — with the support of public officials — agreed to take on about a decade ago, putting more water on the site; rainwater; and remnant process water from the fertilizer operation.
“The water meets water quality standards for marine waters with the exception of pH, total phosphorus, total nitrogen and total ammonia nitrogen,” the state says. “It is slightly acidic, but not at a level that is expected to be a concern, nor is it expected to be toxic.”
Department of Environmental Protection Secretary Noah Valenstein has said the water is not radioactive.
As of Saturday, that wastewater was flowing out to Port Manatee on Tampa Bay at a rate of about 35 million gallons a day.
Estimates suggest there were 480 million gallons of wastewater in the reservoir when the leak began. It is unclear how much could be drained or if the reservoir will collapse before the current incident ends.
County officials have said they are hopeful that even if the reservoir that is leaking bursts completely, other ponds on the site might not follow in the collapse. But they said some of those ponds might have more contamination, whereas the reservoir at the center of the current incident has had fish living in it.
What do we do with phosphogypsum stacks long-term?
This is the question hovering in the background of the present situation at Piney Point. A lot of phosphogypsum, because of its radioactivity, has for decades been limited to the heavily regulated stacks. Last year, the Environmental Protection Agency reversed old policy and said some of the material was safe enough to be used in road construction. A collection of environmentalists disagreed and sued.
Stacks have their own risks, as evidenced by the situation at Piney Point. They are enduring and costly to maintain.
Responsibility for cleaning up the old plant has passed between private owners and the state over the last 20 years. Still the waste remains.
Florida is estimated to have about a billion tons of phosphogypsum kept in about two dozen stacks.