Tampa wastewater officials said Wednesday that Hurricane Hermine's heavy winds and rain led to 1.7 million gallons of raw and partially treated sewage to overflow from the city's system into the bay.
That brings the official total of sewage that last week's storm spilled into Tampa Bay to 30 million gallons — and that figure will only grow.
The City of Tampa's latest figures are nearly double its previously reported figure, but revised numbers aren't unusual after major storms.
Cities across the bay area, including Clearwater and St. Petersburg, say they are still calculating how many gallons of sewage ended up outside treatment plants because of the storm. That often means revised estimates as engineers perform complex calculations to figure out how much sewage flowed out of manholes or from sewer plants overwhelmed by rain, said Department of Environmental Protection spokeswoman Shannon Herbon.
Tampa's spills took place at substations and the city's wastewater treatment plant between Aug. 31 and Friday.
"They weren't long periods of overflow," Tampa Wastewater Department director Eric Weiss said, "but when they did happen, with such high flows you get bigger numbers."
Officials credited a multiyear, $7.3 million job to upgrade a pumping station next to the Tampa Convention Center for reducing the sewage overflow from previous storms.
In St. Petersburg, city officials released a report estimating that it discharged more than 20 million gallons during the storm. However, that figure was also given to the state as of Monday morning, but the sewage dump continued Tuesday and Wednesday.
St. Petersburg officials said they would release more information about the sewage release when the dumping ends. However, no time frame for that end was given.
In Clearwater, officials said they would announce Friday how many gallons of sewage overflowed into the streets of the North Greenwood neighborhood during Hermine.
Pumps at the Marshall Street wastewater treatment plant began failing last Thursday, and sewage gushed from about five manholes, said Public Utilities Director David Porter.
The plant is capable of processing 10 million gallons of wastewater per day, but Hermine's heavy rains pushed at least triple that into the system.
The city had to rent temporary pumps and began installations Thursday. But sewage continued to overflow the plant through Sunday, when it was finally contained.
Porter said there are no meters that could have kept track of the overflow — so officials must guess by calculating the width of the manholes, how many hours they were leaking, how fast the water was gushing and other factors.
"All of our people were working 24 hours a day in shifts to fix this," Porter said. "We worked very hard and around the clock to protect the safety of our customers."