Author(s): Jesse Roman. Published on March 2, 2015.

Case Studies on Resiliency

IN OCTOBER 2012, Hurricane Sandy slammed into New York City. The resulting 14-foot storm surge inundated many subway tunnels and stations with millions of gallons of corrosive seawater. Critical electrical systems were destroyed, underwater tunnels were severely damaged, and miles of tracks had to be replaced. The Metropolitan Transit Authority (MTA) has said it will take roughly $5 billion to return the subway to its pre-Sandy state.

But transportation officials in New York decided that it wouldn’t do much good to simply return the system, with all its now-obvious vulnerabilities, back to how things were. Within six months after the storm, the MTA created the Sandy Recovery and Resiliency Division and tasked it with overseeing the enormous effort to fortify the city’s transit system as part of the ongoing recovery.

“Its more than just rebuilding—we need to dedicate ourselves to building a stronger, more resilient system that can withstand future storms,” New York Governor Andrew Cuomo said in the months after Sandy. He has since called the effort “the most fundamental redesign to the subway system since it was created.”

As of January, the Federal Transportation Authority had allocated $2.9 billion to MTA for repairs, and roughly another $1 billion specifically for resiliency efforts. Many of those efforts overlap, said MTA spokesman Kevin Ortiz.

“This is a two pronged approach—we’re making the system more resilient at the same time we’re making repairs,” Ortiz said. “It’s a process that will be decades in the making.”

While repairing the destroyed South Ferry subway station in Lower Manhattan, for instance, the authority is also taking measures to increase the system's water pumping capacity, water-proof circuit breakers and signal rooms, and install water-tight doors and conduit ceilings, Ortiz said. In the Montague subway tube, which links Brooklyn to Lower Manhattan beneath the East River, $250 million was spent repairing the damage caused by the influx of 27 million gallons of seawater. That included 30,000 feet of new concrete, 75,000 feet of power cable, and 200,000 feet of communication cable to better protect the tunnel and its infrastructure from future storms. While repairing the severely damaged A-line tracks leading to the Far Rockaway section of Brooklyn, the MTA also constructed a seven-foot-high, three-mile-long sea wall made of thick steel to protect the tracks against future storm surges, a fortification project that cost $38 million.

Seawater Floods South Ferry Station
Slideshow of the recovery and rebuilding of the New York City subway by the Metropolitan Transit Authority.

A large chunk of the governor’s stated goal for resiliency is to “flood-proof critical subway elements,” which could mean building additional walls to protect outdoor subway yards, installing submarine-type doors at subway station entrances, designing waterproof covers for ventilation grates, erecting barriers to protect above-ground fan plants, and exploring new technologies to further protect and fortify the city’s subway system.

To underscore the difficulty associated with achieving that level of protection, a recent survey discovered 540 vulnerable openings, from stairways to hatches and vents, in six low-lying subway stations in lower Manhattan—all of which would need to be closed off to prevent flooding in the event of a significant storm.

“What makes it a little bit more challenging is there is no one-size-fits-all solutions to the infrastructure here,” Ortiz said. “The manhole covers, vents, and doors are all different shapes and sizes, and they all need to be fitted.”

To help, the MTA’s Recovery and Resiliency Division has issued 16 task orders to six engineering design firms to study flood-proofing resiliency efforts around the world and investigate how to apply those and other ideas to the challenges facing the New York City subway system. Proposals have come in many forms, such as outfitting low-lying subway stations with removable floodwall panels,
installing mechanical sidewalk grates that could be closed off in a storm, and even huge inflatable bladders that could be blown up inside subway tunnels to keep water out during a storm.

“We don’t want to limit ourselves,” Ortiz said. “New technology and solutions pop up every day.”

JESSE ROMAN is staff writer for NFPA Journal.