The release of at least 17 million gallons of wastewater into Manatee County waters in the first 24 hours after Hurricane Ian would normally be a standout event for those who keep a close eye on water quality.
But it’s just one of many pieces in the pollution puzzle after Ian clobbered Florida.
“It’s not good — but it’s been dwarfed by all the rainfall we’ve gotten,” said Dave Tomasko, executive director of the Sarasota Bay Estuary Program. “We believe we’ve had multiple tens of billions of gallons of runoff” entering Sarasota Bay.
As researchers start to piece together the storm’s environmental toll, some conclusions already are clear.
For one, Tampa Bay was largely spared the worst. But rainfall that fell over the lower bay, about six inches compared to Sarasota Bay’s 11 or more, still could fuel poorer water quality conditions in the lower watershed, according to Ed Sherwood, executive director of the Tampa Bay Estuary Program.
In the first day after landfall, enough wastewater spilled into the Lower Tampa Bay watershed from Manatee County to fill more than 25 Olympic swimming pools.
The plumes of runoff leaving Southwest Florida in the days after Ian were so large that they could be seen from space. Freshwater plants like duckweed and water hyacinth, normally found in inland Florida waters, were still floating in the Gulf of Mexico about 2 miles offshore this week, Tomasko said.
The contents of all that runoff, and what it may mean for algal blooms and future environmental and human health, are just beginning to come into view: decomposing plants and animals; fecal bacteria; grass clippings; dog poop; gasoline; sewage and anything else that may have been swept up from urban areas during the storm.
Once‐sparkling waters now resemble root beer. A week after Ian, salinity levels were about half their normal average in the lower Sarasota Bay, according to the Sarasota Bay Estuary Program’s data.
“If those conditions last long enough, you can kill off the clams and worms and small fish that live on the bottom,” Tomasko said.
Wastewater spills flare up during, after Ian
Wastewater spills are just one part of those poor conditions.
Staff at a Bradenton water treatment facility first informed Jim McLellan, the Bradenton public works director, about a potential spill on Sept. 28 as Hurricane Ian was bearing down on Southwest Florida.
Rising groundwater entered through cracks in underground sewage pipes, which caused filters to clog and swell the system, McLellan said.
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What resulted was about 18 hours of partially treated wastewater pouring into the Manatee River, which was estimated to total more than 13 million gallons. At roughly the same time, a backup generator failed at a separate lift station, resulting in 4 million gallons of sewage entering Wares Creek south of downtown Bradenton, according to McLellan.
“It was not a normal event, by any stretch of the imagination,” he said.
To the north, wastewater pumps throughout Hillsborough County also started overflowing after power outages streaked across the region.
At least 330,000 gallons of wastewater — enough to fill more than 13 average swimming pools — were spilled into Tampa waters over an 18-hour period that ended on Sept. 29, according to Florida Department of Environmental Protection reports filed by the City of Tampa Wastewater Department.
In one instance, a pumping station at Adamo Acres off Lime Tree Road in Tampa lost power for 18 hours during the storm. Crews were able to fire up a backup generator, but more than 138,000 gallons of wastewater already had been dumped into a ditch that flows into the Palm River, then into the Hillsborough Bay, according to state environment records.
Response teams were “unable to collect any of the overflow,” and signs warning of the spill were posted along the Palm River, records show.
Will Ian impact Red Tide?
It’s still too early to tell what impacts the post‐Ian runoff, including sewage spills, may have on Red Tide blooms, according to Kate Hubbard, director of the Florida Fish and Wildlife Conservation Commission’s Center for Red Tide Research. Conditions are most ripe for the harmful algal blooms from September to January.
“Obviously we’ll be keeping a close watch: We’re in that right window, but it’s hard to say because generally there’s a lot that goes into the water after a storm like this,” Hubbard said. “There’s also a lot of energy, and where that energy goes is something we’ll be tracking for a long time.”
Plenty of water moves around after a Category 4 storm: Wind energy helps mix the water column, it causes currents to shift, and that can translate into ocean energy that can determine if Red Tide gets carried toward shore, Hubbard said.
All the freshwater runoff may have at least one silver lining when it clashes with a saltier gulf: The species that causes Red Tide, karenia brevis, has trouble tolerating low-salinity environments for long periods of time, according to Richard Stumpf, an oceanographer at the National Oceanic and Atmospheric Administration.
In the first days after the hurricane, a research vessel detected trace amounts of the Red Tide organism about 30 miles offshore of Tampa Bay, Hubbard said. But from Clearwater down to Englewood, there was a “very low” risk of Red Tide in model runs early Friday morning, according to the federal Gulf of Mexico Harmful Algal Bloom Forecast.
“Conditions have been changing back and forth since Ian passed,” Hubbard said. “We are continuing to keep a really close watch on things.”