ST. PETERSBURG — The Sunshine City is more like the Leaky City.
On an average day without rain, about two-thirds of St. Petersburg's sewage flow is made up of groundwater entering leaky sewer pipes, consultants told the City Council on Thursday.
But when it rains, those leaky pipes are deluged. That results in a spike of sewage, overwhelming the city's sewer system.
Those ancient, overwhelmed pipes appear to be one of the major factors behind the 200 million gallons of waste released during St. Petersburg's 14-month sewage crisis, according to a preliminary analysis by a wastewater consultant.
The study is based on the three weeks of rain that saturated the city in August 2015. Once the consultants gather all the data, they'll be able to simulate various rain scenarios that could cause the kinds of problems that resulted from Tropical Storm Colin and Hurricane Hermine.
The analysis found that aging, leaky pipes are present in much of the city. Critically damaged parts of the system are concentrated in areas around Lake Maggiore, Old Southeast and the west-central areas of the city.
That bad news actually eased City Council member Karl Nurse's mind. That's because now the city can focus on fixing those pipes.
"It makes this a much less overwhelming task," Nurse said.
Nurse wants the city to spend as much money that is budgeted for sewer repairs as quickly as possible.
Public works administrator Claude Tankersley said that he wants to spend all of the $8 million recently designated by the city for pipe lining and other fixes before the start of next summer's rainy season.
The city has already said it will attempt to reopen the shuttered Albert Whitted sewer plant by June to help avoid the kind of overflows that have befouled Tampa Bay and Boca Ciega Bay.
CH2M Hill, a national engineering consulting firm, has been studying the city's sewers since the first spills and dumps in August 2015. On Thursday, a consultant said the second phase of the study would complete its data collection in December. A "stress test" for the whole system will be done in August.
The firm's study monitors 82 points around the city and neighboring beach towns that send their sewage to St. Petersburg for treatment.
Water gets into the sewers in various ways. Manholes that don't have proper covering allow water to seep into the lines. Private sewer lines are also notorious for allowing groundwater in, although there isn't data yet on whether that's the case in St. Petersburg.
And then there is the age of the pipes themselves. Some are up to a century old. Others are made of "orangeburg," a type of sewer pipe popular until the 1960s made of pressed wood pulp and pitch. Those lines are well past being useful, Tankersley said.
Even on dry days, about 24 million gallons of groundwater seeps into the sewers. That's about double the 12 million gallons or so of human waste that makes its way through the system, Tankersley said.
The city has a sewage capacity of 56 million gallons during an average day. But during Hermine, the system saw peak flows of up to 150 million gallons a day, much of which ended up in waterways and roadways.
Tankersley, who was hired in February, said he believes this is the first systematic study of the 900 miles or so of sewer pipes that run beneath the city's streets.
His predecessor, Mike Connors, retired last year after the first spills. Last month, Mayor Rick Kriseman placed water resources director Steve Leavitt and engineering director Tom Gibson on unpaid leave in connection with the city's sewage issues, which are being investigated by the Florida Department of Environmental Protection.
One of the conclusions that surprised council member Charlie Gerdes was the amount of groundwater that — even on rainless days — ends up in the city's sewer pipes.
"That's mind-blowing," he said.
Contact Charlie Frago at firstname.lastname@example.org or (727) 893-8450. Follow @CharlieFrago.