Piney Point Pollution Will Linger in Tampa Bay For Months, Scientists Say

WUSF | By Kerry Sheridan

Published April 15, 2021 at 6:47 AM EDT

A computer model devised at the University of South Florida is tracking pollution from the Piney Point phosphate plant. Highly concentrated pollution is in yellow, with dispersed pollutants in lighter blue.

Powerful, sustained winds are rare this time of year in Florida, and that means the polluted water that spilled from the Piney Point phosphate plant last month is likely to linger in Tampa Bay for months, a USF ocean physicist said Wednesday.

“Every time the tide sloshes to the north or to the south, this plume is going to spread a little bit more to the north and to the south,” said Bob Weisberg, a professor of physical oceanography at the College of Marine Science at USF.

“And depending on how the winds are blowing, it will disperse towards the other side of the bay,” he said.

In late March, a retention pond at the plant began to leak, and more than 200 million gallons of wastewater spilled into Tampa Bay.

The leak has since been temporarily fixed, and Governor Ron DeSantis plans to close the troubled site for good.

Meanwhile, the impact of the spill remains unclear.

To track the movement of the water in Tampa Bay, Weisberg and his team are using the Tampa Bay Coastal Ocean Model, which also forecasted how the region would respond to Hurricane Irma in 2018, and how red tide moves through the ocean.

Now, the same approach is being used to forecast the dispersal of effluent water released from Piney Point.

The model shows a lot of back-and-forth movement of the polluted water, like water in a bathtub, but not a quick dispersal. The highest nutrient concentrations are still present along lower Tampa Bay’s southeast coast.

Weisberg said the discharge water is slowly moving south from Port Manatee. It can be found as far north as Little Manatee River, and as far south as Manatee River. Low concentrations of the effluent have already reached St. Petersburg and the Gulf of Mexico.

Weisberg and his team are working on refining a forecast that will show how long the pollution is expected to stick around.

“There will be low concentrations of the Piney Point effluent in the bay as it spreads out for months,” he said.

The key, he added, is understanding what levels of pollutants are in the water – scientists are still working on that – and knowing the level at which the concentration of those pollutants is no longer a concern.

Weisberg and some of his students took his sailboat out last week to see the state of the Tampa Bay’s water for themselves.

“The water was nice and green when we first started out,” he said.

“Maybe about a mile from Port Manatee, you know, I'm sailing the boat, watching what I'm doing. One of my students said, ‘Hey, take a look at the water.’ It was just a dark brown.

“It was a very visible contrast once we got into the higher concentration effluent.”

The brown color comes from excess plant life, growing as a result of the nutrients in the wastewater, Weisberg said. Scientists are still studying the environmental damage that could cause.