The official tally of sewage dumped into the streets and waterways of Tampa Bay keeps growing.
Clearwater reported Friday that its overwhelmed system spilled an estimated 31.7 million gallons of diluted sewage as Hurricane Hermine drenched the state last week.
Largo officials said the city released 24.4 million gallons. That number does not include nine of the city's 23 spills that the city was not yet able to count.
That brings the latest total for the area to 85.1 million gallons, which will almost certainly rise as municipalities release more reports and adjust their figures even higher.
Earlier in the week, Pinellas County said it released 7.3 million gallons and the city of Tampa discharged 1.7 million gallons. But the biggest offender by far is likely to remain the City of St. Petersburg.
Officials there said they had discharged more than 20 million gallons by Monday morning — but that was the sixth day of 10 straight days of sewage discharges.
St. Petersburg officials said they stopped discharging waste through a pipe into the bay at 4 a.m. Friday. They also acknowledged Thursday that a malfunction may prevent them from ever knowing exactly how many millions of gallons were spilled.
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Clearwater officials said diluted sewage gushed from 18 manholes throughout the city, pushing about 3 million gallons into Old Tampa Bay and 29 million gallons into Clearwater Harbor through the stormwater system or by surface water tributary.
A mechanical failure beginning Sept. 1 at the sewage pumping station in North Greenwood — caused by water seeping into the electrical system — was responsible for most of the spill. Staff installed a temporary pumping system and most of the manholes had stopped overflowing by Sunday, with one leaking until Wednesday.
The city's wastewater system is typically able to handle severe storms without overflow, but Hermine's heavy rainfall, coupled with the North Greenwood plant's mechanical failure "were challenges we could not overcome," said Public Utilities director David Porter.
Without meters to gauge the overflow that seeped from Clearwater's system, Porter said most of the discharge had to be estimated by calculating the speed of flow and length of time it gushed with the size of the manholes.
"It's the size of the manhole and the volume of water we observed leaving over time," he said. "That's all you can do."
Because most of the sewage that gushed from the manholes flowed into the stormwater system through drains in the roads, Clearwater is testing for fecal bacteria at seven locations.
Water from the stormwater drains discharges into ponds or other surface waters, such as Stevenson Creek, before eventually flowing to Old Tampa Bay and Clearwater Harbor.
But by that time, "it has been diluted so many times along the way that our influence out there is going to be very, very, very minimal," Porter said.
One of the seven stormwater discharge sites being tested is on the shoreline of Clearwater Harbor near a manhole.
The only area around Clearwater Harbor tested by the Florida Department of Health in Pinellas is at Sand Key. The last test conducted Tuesday came back "good," according to spokesperson Maggie Hall.
City Manager Bill Horne said officials are working to determine what caused the failure at the North Greenwood plant. He said much of the overflow could have been avoided if it had functioned properly.
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Irvin Kety, Largo's environmental services director, said his city released 11.9 million gallons from the city's wastewater treatment plant in a controlled discharged. The sewage had received all three stages of treatment, but all the chlorine had not been removed before it was dumped into Cross Bayou, eventually emptying into Tampa Bay.
Chlorine could be harmful to marine life, but Kety said the industrial nature of the canal near the sewage plant hasn't been a nature hot spot. The chlorine should have quickly been neutralized by the high stormwater flows long before it reached Tampa Bay, he said.
Overall, he said about half of the 24.4 million gallons discharged by Largo was untreated sewage released through its manholes. The figure is higher, but flow from nine manholes wasn't measured because crews were busy trying to keep sewage out of residents' homes, he said, in a storm that dropped 20 inches of rain in some parts of the city.
Those amount of those nine discharges were labeled "unknown."
Contact Tracey McManus at email@example.com or (727) 445-4151. Follow @TroMcManus.
31.7 million gallons of diluted sewage estimated to be spilled by Clearwater
18 Manholes that spewed sewage in Clearwater
24.4 million gallons of "sewage overflows" reported by Largo
9 Spills that Largo listed as "unknown" amounts