ST. PETERSBURG — When asked about rumors of a sewage dump, Mayor Rick Kriseman's spokesman said Monday that he wasn't aware of it and needed to check. Within an hour, the spokesman called back with news. Over the weekend, St. Petersburg discharged millions of gallons of treated sewage into Tampa Bay, Ben Kirby said. Two days later, Kirby backtracked. On Wednesday, he said the city had pumped only one-fifth of the amount of sewage that he had said earlier. But it was far dirtier than what he initially disclosed. The confusion over the nature of this weekend's discharge is drawing attention to St. Petersburg's wastewater system, which suddenly looks susceptible to major rainfalls. So far in August, the city has dumped 16.5 million gallons of untreated, or partially treated, sewage into Boca Ciega and Tampa bays. On Wednesday, officials conceded that dumpings could continue for at least a year because St. Petersburg's aging and overloaded system can't handle the rainfall. This admission comes four months after city officials closed a wastewater plant near Albert Whitted airport. Public Works director Mike Connors argued for that plant's closure, saying the Southwest wastewater treatment plant near Eckerd College could handle the increased flow. But the Southwest plant proved unequal to the task, forcing the dumping of 15.4 million gallons of untreated sewage into Clam Bayou last week. "It's abundantly clear they failed to do adequate planning," said council member Darden Rice. When another bout of heavy rain overwhelmed city sewer pipes and pumps last weekend, Kriseman gave an order: no more discharges into Clam Bayou. City workers scrambled to reopen the Whitted plant. Temporary pumps were used to fill up six tanks — with a combined capacity of about 4.4 million gallons — at the plant. But the plant, missing much of its cleaning equipment, quickly reached capacity, prompting the eventual discharge of dirty water into Tampa Bay. Rainwater diluted the sewage, but only about a quarter of the usual amount of chlorine was applied and it was given minimal aeration, said Steve Leavitt, the city's water resources director. The aerators, operating a lower speeds, "provided essentially no treatment," he said. Leavitt said the subsequent discharge was cleansed to about a quarter of the normal standard. Testing done by the city in Tampa Bay found a low amount of bacteria, which fell well below levels that would require closing beaches, Leavitt said. Kirby said he initially mischaracterized the amount of discharge because he was told by wastewater officials that it was 5.5 million gallons. That amount was pumped into the Whitted plant, but only 1.1 million gallons ended up in the bay. Kirby denied on Monday that the sewage was untreated and provided detail about how it was treated. Yet on Wednesday, Kirby conceded that the wastewater was only partly treated. He said he assumed the reporter knew that the sewage couldn't be completely treated in an emergency. The major lesson learned in the past week has been a lack of coordinated emergency response to severe weather, Rice said. "It appears there was no type of system in place that works," Rice said. The city has capacity for 56 million gallons of wastewater. During the worst of the rains the daily flow was 80 million gallons, Leavitt said. Keeping the Albert Whitted plant open wouldn't have solved the problem, Leavitt said. But, he conceded, "It would have helped." Kriseman and Connors, who oversees the wastewater system, don't regret closing the plant, said Kirby. Questions about whether the recent discharges could have been avoided or lessened is "speculative," he said. "They're looking forward," Kirby said. But city officials concede the near future doesn't hold any major improvements. The demolition of the Albert Whitted plant has been put on hold until the Southwest plant's expansion is complete. The city has just started to build a 15-million-gallon tank at the city's Southwest wastewater plant, but that won't be completed until July 2016, Leavitt said. "We're damn sure not pumping any more sewage into Boca Ciega Bay," Kirby said. What about pumping more partially treated waste into Tampa Bay? "Only if we got another major overflow," he said. Late Wednesday, WTSP 10Weather reported a flood watch for today as another round of storms approached. Contact Charlie Frago at [email protected] or (727) 893-8459. Follow @CharlieFrago.