With nearly all of its huge underground tunnels finished, Charleston’s Spring-Fishburne drainage project can already whisk 1 million gallons of stormwater from city streets in just four minutes, with gravity alone powering the flow.
That’s about 10 times as much water as the old system. Residents near the medical district and Septima P. Clark Parkway say they’ve already seen a marked reduction in flooding.
But the project’s full potential won’t be realized until crews install three giant pumps, open another deep tunnel and build a pump house.
That pushes back the project’s finish line another year, from late 2024 until late 2025 — or two-and-a-half more hurricane seasons.
The project’s progress and latest delay highlight another issue: growing demand for large water pumps as low-lying cities across the world scramble for equipment amid rising seas and stronger storms, industry officials and experts say.
“We have this great tunneling and pump system being brought to the finish line,” said William J. Davis, head of The Citadel’s Civil and Environmental Engineering department. “But we’re going to need more of them.”
THE SPRING-FISHBURNE DRAINAGE BASIN: Most of this drainage basin is a former marsh that was filled in beginning over a hundred years ago. No longer a natural drainage barrier for the peninsula, it frequently floods. (SOURCE: CITY OF CHARLESTON; ESRI)
Monster pumps
When complete, the Spring-Fishburne project will drain a large area around the Septima P. Clark Parkway, known locally as the Crosstown, a key artery that funnels motorists from North Charleston, Mount Pleasant and West Ashley into the heart of Charleston's peninsula. It will serve much of the medical district, which contains three medical centers that employ 25,000 people and treat 400,000 patients a year.
Like an iceberg, most of the project's features are hidden below the surface. It has shafts that drop as deep as 169 feet and 12-foot-wide tunnels connecting them. It has systems that spin stormwater into powerful vortexes, wringing air from the water as it swirls down the shafts. These whirlpools allow more water to move toward a wetwell, or holding area, and then into the Ashley River.
It's an underground plumbing system on an outsized scale. The bulk of the work began in 2016, as crews descended deep below the peninsula with giant boring machines. They dug about 9,000 feet of tunnels. Then, beginning late last year and in January, crews finally began removing concrete bulkheads that kept the tunnels dry while work was underway, said Steve Kirk, project manager for the city.
This finally allowed the tunnels to do what they were designed to do — drain stormwater from the peninsula's streets. For the time being, gravity will power this new system. Even without the pumps, the tunnels funnel a tremendous amount of water into the Ashley River.
The old stormwater drains removed 36,000 gallons a minute. At that rate, it would take 18 minutes to fill an Olympic swimming pool. With gravity alone, the new system could fill that pool in less than three minutes.
The pumps will add even more capacity, and they "are monsters," Kirk said.
Xylem Inc., headquartered in Washington, D.C., is designing and manufacturing the trio of pumps. Each will be four-stories tall and powered by a 950-horsepower engine. The city is paying $6.1 million for those pumps and engines. When running, the pumps will remove three times as much water as the deep tunnel system serving the city’s tourism-driven Market area.
Matthew Fountain, the city’s stormwater manager, said that as far as he knows, the Spring-Fishburne pump station may be the largest in South Carolina.
At times, though, the project has resembled a slow-moving drain. Last year, The Post and Courier's "Tunnel of Trouble" investigation revealed how a cascade of construction failures and natural disasters set the project back three years and pushed it $44 million over budget. The newspaper’s report revealed how contractors were slow to hire qualified workers and had difficulty retaining them. Workers had to deal with toxic gases, contaminated soil and old graves. Flooding rains hit year after year, simultaneously slowing progress on the tunnels while underscoring the urgent need for them.
In mid-2022, city officials expected the pumps to be installed by the end of 2024. That timeline slipped a year, in part because the pumps are custom-made, Fountain and Kirk said. They now expect the pumps to arrive in late 2024, and that it will take another year to prepare and finish the pump house. Crews also are wrapping up another tunnel extension that will speed drainage near MUSC.
The project, Kirk said, has been a lesson in solving unexpected problems.
This aerial view of the Spring-Fishburne project's wet well, shows the flood mitigation project's silt removal unit, discharge pump piping and bar screens that stop trash in stormwater from being dumped into the Ashley River. This station, between the Ashley River bridges, is also where the pumps will eventually be housed to pump 1 million gallons of water every three minutes from the area around the Crosstown. Provided
Pumped up demand
One of these problems has been a global manufacturing backlog, propelled in part by the COVID-19 shutdowns and rising demand for climate change-related work.
Xylem had an order backlog of $1.9 billion at the end of 2019, shortly before the pandemic began. At the end of 2022, its backlog had doubled to $3.6 billion, according to federal filings. The company declined to comment and referred questions about the pumps to Charleston officials.
But the backlog shouldn’t come as a surprise, industry and climate experts say. Global warming is making sea levels rise faster than in the past along with fueling stronger rainstorms. This, in turn, is putting more pressure on industries to ramp up production of pumps and other flood control equipment, said David Fuente, a professor with the University of South Carolina’s School of Earth, Ocean and Environment.
“This will take time, and I suspect delays and increased prices will persist in the near term,” he said.
Dana Eller, head of Moving Water Industries, another large American pump manufacturer, is counting on this demand. Eller’s great-grandfather founded the company in South Florida in 1926. Eller said his company is doubling its capacity over the next five years, the largest expansion in its history.
Eller said large stormwater pumps are more complex than many people realize. “They’re not like your basement sump pump.” Many must be designed specifically for a particular city’s needs and may take nine months to manufacture, he said, adding that his company made stormwater pumps for Hilton Head with stainless steel parts because of the Lowcountry's brackish water.
Building factories to make these pumps is challenging, as well, he said. It might take two years or more to enlarge a factory space. Finding and training qualified workers may be even more difficult. But he said he is confident in the industry's trajectory, especially after Congress passed the Inflation Reduction Act, which injected billions of dollars into programs to help communities better adapt to flooding.
With stronger storms and rising sea levels, “I think there will be enough business out there for everyone,” he said.
Tony Glover says flooding in the Spring-Fishburne area of downtown Charleston has gotten a little better since a series of deep tunnels were completed, but flooding is still a nuisance. Tony Bartelme/Staff
Higher water, lower capacity
Industry experts cited another factor driving demand: As seas rise, stormwater systems that depend on gravity alone will become less effective, highlighting the need for more pumps.
Charleston’s tides dependably show this dynamic twice a day. At high tide, many of the city’s stormwater pipes and ditches fill with seawater. If it rains, stormwater has nowhere to go. Residents can end up knee-deep in floodwaters after a half-hour deluge. Then, as tidal levels go down, drainage typically speeds up like an unclogged pipe.
The Spring-Fishburne project also shows this process in action. Without pumps, it drains about 140,000 gallons per minute at high tide, said Kirk, the city's project manager. But at low tide, that capacity grows to 250,000 gallons per minute.
“That’s a reminder of why we need the pumping system,” he said.
When in place, those pumps will all but guarantee the drainage rate of 360,000 gallons per minute whether the tide is high or low, Kirk said. At low tide, the system will let gravity do all the work, and the pumps automatically kick in during cloudbursts at higher tides. The city also designed the system to take into account a 2.5-foot overall rise in the sea level in the future.
When the city hits that 2.5-foot mark remains a moving target. The sea level in Charleston rose about 1 foot over the past century, a rate that began to accelerate in the 1970s, researchers discovered. Where the sea once rose a manageable inch or less per decade, it increased 2 inches between 2000 and 2010. Now the rate is nearly 3 inches a decade. Apply this accelerating curve to real life, and you have an explanation for the record-breaking increases in sunny day floods – and the need for more stormwater pumps.
For now, with the Spring-Fishburne pumps still more than two years from going online, the gravity-powered deep tunnels have made a big difference for longtime residents, such as Tony Glover.
Glover, 46, sat on a folding chair near the intersection of Line and President streets on a recent afternoon, about an hour after a cloudburst over the medical district. Harold Green, 66, stopped by to say hello. The two talked about how floodwaters ruined cars over the years but also kept housing in the area more affordable. The morning's squall had dropped nearly an inch in less than an hour.
"After a rain like that, the street would have flooded," Glover said. But around them now, the streets were merely damp, with just a smattering of puddles to remind them of the storm before.
