The infiltration was monitored and inspected for any leaks for five consecutive days before workers proceeded to install the spiral-wound liner past this section into the interceptor sewer.
Photo by YOR/JWP, courtesy the New York Dept. of Design and Construction

“It would be noisy and dangerous and require closing the street for months, if not years,” says Iyad Marzouq, the agency director of infrastructure. “The design also would have to consider the FDR Drive foundations, any number of adjacent utility lines and other factors.”

Marzouq adds that disabling the interceptor for an extended period would require a temporary bypass and pump system to provide round-the-clock in-series pumping of the 40 million gallon daily flow, adding at least $12 million to the project’s overall cost.

By the end of 2024, however, few people living in or driving through the neighborhood likely realized that the nearly $29-million interceptor rehabilitation project was taking place beneath their feet and was well on its way to completion, which is expected this year.

Workers installed uniform liner material in the interceptor sewer and successfully lined past the infiltration repair that was plated, completing nearly 350 ft of uniform lined sewer. 
Photo by YOR/JWP, courtesy the New York Dept. of Design and Construction

The key is the city’s decision to use an innovative trenchless construction method called spiral wound lining, in which a continuous strip of polyvinyl chloride (PVC) is mechanically wound through a pipeline to form a uniform liner. A cementitious grout is then pumped into void space between the new rounded liner and existing rectangular sewer structure.

Spiral wound lining was one of several repair and relining alternatives the department had carefully evaluated for several years to address the interceptor’s many problems. Unlike other trenchless methods that would have significantly reduced interceptor capacity, the spiral wound lining process can occur in wet conditions using submersible equipment tailored to the pipeline’s configuration. This allows the interceptor to remain in service during construction.

David Beesley, vice president and project manager at contractor Coppola Services, Ridgewood, N.J., says flow velocity is the critical factor. “As long as velocities are in the 1- to 2-feet per second range, we can work safely in flow levels up to about 18 to 24 inches,” he says.

To help ensure optimal working conditions, Coppola scheduled work for the overnight hours when flow levels normally are lower, installing a 30-linear-ft partial bypass line to temporarily redirect 17.6 million gallons of daily interceptor flow to a neighboring, smaller-diameter parallel sewer line while work was taking place.

After each shift, the lining equipment would be de-energized and the interceptor returned to full capacity. “Some nights, the level would be as low as 6 inches,” Beesley says.

Because the South Street interceptor would be unlike any previous spiral wound lining projects, Coppola prepared for the work by using a mock-up of the interceptor that was built in the company’s equipment yard.

“We had not done a mock-up of that scale before, but we wanted to be ready for what we would encounter on South Street,” Beesley says.

The team resolved the issue of building bulkheads within the narrow conditions by excavating or chipping the existing host interceptor sewer pipe by about 1.5 in. all around, which created room to install bulkhead walls with brick and mortar.
Photo by YOR/JWP, courtesy the New York Dept. of Design and Construction

Ironing Out Issues

Even with the extensive preparation, the South Street interceptor project posed no shortage of surprises—including a 10-month multi-agency permitting and coordinating process that also required approval by the city’s Dept. of Environmental Protection, which operates the sewer system. Construction finally began in early 2024 with the partial bypass connection. By May, Coppola was ready to begin lining work five nights a week, with a goal to average about 20 linear ft per shift.

“On some nights, we’d get the production we expected, but on others, just a fraction of it,” Beesley says, citing debris from the line’s normal-period flows as a constant challenge. “Things build up so fast, particularly due to the way the machine is positioned,” he explains. “Keeping the equipment clean proved more time-consuming than we originally anticipated.”

Weather has been another concern. Added stormwater from heavy rains occasionally has cost the team all or part of a shift. Coppola also encountered unforeseen changes in interceptor dimensions due to aged irregular material and sediment buildup that required workers to chip away concrete from the walls and ceiling so lining machinery could pass through.

The project located near the South Street Seaport in lower Manhattan involves the city’s first use of spiral-wound lining that allows the team to fix a major sewer leak without digging a trench.
Image courtesy the New York Dept. of Design and Construction

While the Coppola team adapted to the conditions and made gradual progress installing the lining, the project’s most significant issue awaited at about the 300-ft point—a 3-in. by 8-in. wall cavity that each minute spewed as much as 100 gallons of water from the East River into the sewer.

Marzouq says the leak, which was the project’s main catalyst, repeatedly defied team attempts for a permanent fix. “It was like applying a bandage,” he says. “Because there was so much pressure from the river, everything we tried seemed to fail within a few days.”

After four months of trial and error, the department says the cavity was finally sealed using a combination of hydrophobic material and expandable moisture-activated resins. These were then covered with fast-setting hydraulic cement and wire mesh. The final step, bolting a 96-in. x 43-in. aluminum metal plate to the interceptor wall, was completed well before Coppola’s lining machine arrived.

“The leak didn’t delay that part of the work at all,” Beesley says, adding that the repair approach will likely be used again for another infiltration leak further down the interceptor.

Installing spiral-wound lining involves using a waterproof machine, constructed in the sewer, to create a new structure within the existing one.
Image courtesy the New York Dept. of Design and Construction

Gaining Momentum

By the end of 2024, Coppola was nearing the halfway point of the lining installation and had begun grouting work. Plans call for the lining of the remaining section of interceptor to be complete this summer.

So far, the department is pleased with how spiral wound lining has performed. Marzouq sees other potential applications for more city underground infrastructure rehabilitation projects where an open-cut approach would be problematic. “The project is providing a lot of lessons that should help things move more quickly in the future,” he says.

“There’s no way you could do a project like this with a conventional method,” Beesley adds, noting that the project team encountered a host of utilities in simply digging down 20 in. to install the bypass line.

“At least we could cover that cut with plates and keep the street open,” he says. “Going 30 feet underground for the entire length of the project would require massive excavation—and there’s no telling what you would find along the way.”