Story of a sewage overflow — a tropical storm, a low spot in the pipe and some bad timing
Had Tropical Storm Colin sloshed by the Tampa Bay area a month later than it did, the sewage overflow that Tampa saw Tuesday morning probably wouldn’t have been as bad, a city official said Wednesday.
That’s because the city is close to finishing a $7.3 million, multi-year project to upgrade a wastewater pumping station that is designed to keep wastewater flowing and minimize the kind of backup that took place just north of the Columbus Drive bridge.
“It increases the capacity by about 20 percent,” Tampa Wastewater Director Eric Weiss said of the expanded pumping station, which is located near the Tampa Convention Center. “At a minimum, it will significantly help.”
Testing at the pump station was scheduled to take place Tuesday. Instead, as Colin dumped rain on Tampa, wastewater officials started getting readings that wastewater was rising fast inside a boxlike structure on Charter Street in the Riverside Heights neighborhood. One pipe empties wastewater into the structure, while another leading out of the box carries the sewage under the river on its way to the city's Howard F. Curren Wastewater Treatment Plant.
“It was going up several inches every five minutes,” Weiss said.
Because the pipe goes under the river, it’s a natural low spot in the system, Weiss said. And if wastewater starts to back up anywhere, a low spot is a leading candidate for an overflow. Between 7:25 and 9:23 a.m., an estimated 352,000 gallons of untreated sewage flowed into the river about 1,000 feet north of the Columbus Drive bridge. (Wastewater employees managed to capture some of it before it reached the river.)
City officials notified the Hillsborough County Environmental Protection Commission and Florida Department of Environmental Regulation of the spill within a required four-hour period.
One thing Tampa didn’t do was notify its wastewater customers and ask them — as St. Pete Beach did after a wastewater discharge there — to refrain from taking showers, washing dishes or flushing toilets unnecessarily in order to reduce the amount of water going into the system.
Under the circumstances, “any call like that we would have put out wouldn’t have helped,” Weiss said. Mayor Bob Buckhorn said he wasn’t aware of the spill himself until learning about it from news reports. “I’ve got to get more details on that,” he told a reporter Wednesday morning.
In addition to bringing the reconstructed pumping station online, Tampa officials said they are looking into coordinating the work of pumping stations upstream to slow the flow of wastewater in the future in similar circumstances.
“In other words, don’t pump too much all at once,” said Brad Baird, the city’s administrator for public works and utility services. “Hold some of it back” so “you can smooth out that flow better. … If you’re getting some ‘high water’ alarms, you’ve got to see where you have your storage.”
Still, with 230 pumping stations citywide, it is a complicated network.
Another factor contributing to the overflow was the sheer volume of rain falling on the city. Storm water gets into the sewer system in a variety of ways — through cracks in pipes and manhole covers on flooded streets — forcing wastewater out in the process.
Tampa’s treatment plant handles an average of 64 million gallons of wastewater a day and is permitted to handle up to 200 million gallons a day. At its peak on Tuesday, wastewater was coming in at a rate that would have brought 148 million gallons to the plant over a 24-hour period. (It ended up getting 97 million gallons of wastewater for the day.)
Since the incident, the city has tested the river for contamination in the area of the overflow as well as upriver and downstream. Weiss said readings showed generally higher fecal coliform counts in all parts of the river, which he said likely reflected the huge inflows driven by the storm. But, he said, there were no hotspots of contamination near the spill site or anywhere else. The city plans to do another round of water quality testing on Thursday.
In the long run, Buckhorn said improving the city’s storm water drainage system — something the city is looking to do through a new property assessment to cover the cost of new projects to ease flooding — could ease the strain on the wastewater system.
“Obviously, we’ve got an aging system,” Buckhorn said. “We’re trying to invest in that system. We need City Council to approve those types of investments.”