Could New York City Subways Survive Another Hurricane?

A good place to see how and why the Metropolitan Transportation Authority just barely survived Sandy last fall is the entrance to a tunnel at 148th Street and Lenox Avenue, in Central Harlem, where, just before the storm hit, a crew of carpenters built a plywood dam 8½ feet tall by about 55 feet wide. That ad hoc, low-tech, last-minute construction held the New York Harbor at bay and not only saved the city hundreds of millions of dollars, but also made it possible for the subway to come back to life as quickly as it did.

Illustration by Wesley Allsbrook

M.T.A. workers hauling sandbags into a subway entrance as part of a makeshift dam.

Illustration by Wesley Allsbrook

The M.T.A. Rail Control Center, where all the boards went gray.

The first work on the dam began a week before Sandy arrived, when building materials were taken to the site. As weather forecasters were hemming and hawing about European versus American climate models and Mayor Bloomberg was debating whether to evacuate flood areas, New York City Transit was working on its own hurricane plans. "You scramble your jets right away — you can't wait," says Thomas F. Prendergast, president of New York City Transit at the time and now the authority's chairman and chief executive. The reports on the dam that he was getting at the Rail Control Center in Midtown showed the level getting higher and higher. "The water was lapping at the top," he says.

Not long after Sandy was categorized a tropical depression off the coast of Venezuela on Friday, Oct. 19, the M.T.A. had begun gathering cots and bedding, food and water, for track workers and hydraulics teams and even the train crews that would shut the system down and start it back up. Carpenters and bus drivers alike would be staying at depots and temporary shelters, because there would be no way for them to go home and then return to work while the subways and regional trains like Metro-North Railroad and New Jersey Transit were out. By Wednesday, when Sandy crossed the island of Jamaica as a Category 1 hurricane, carpenters were covering sidewalk subway grates with plastic sheeting and plywood and building barriers at the entrances of low-lying subway stations, mostly in Lower Manhattan.

On Sunday, as Sandy moved up the East Coast, Governor Cuomo announced the closing of the subway system. "Now it is time to take action," he said. Transit put its trains on tracks between stations north of 59th Street, where many tunnels are at a flood-safe elevations. Engineers and conductors walked back along the tracks to be picked up by the dwindling number of trains still running.

At the 148th Street Station, in Central Harlem — the northern terminus of the Seventh Avenue line, a.k.a. the No. 3 line, and the point where the tracks go underground beneath Lenox Avenue — Frank Jezycki was watching carpenters build the dam. Jezycki is in charge of all subway maintenance, which includes tunnels, elevated structures, fans and pumps. Pumps are always going; on a dry day, the system takes in 13 million gallons of water that pour into it from underground streams and other sources. "My area is responsible to, first, try to mitigate the water coming in," Jezycki says, "and, second, to get rid of the water once it comes in."

Jezycki had recently been going all around the subway system — "That guy Frank," a hydraulics worker said, "he's a machine!" — but now he was focusing on the dam-building as the timbers, plywood and sandbags were moved, fire-brigade style, from the M.T.A. yard at Lenox Avenue down to the tunnel's opening. There were already two vertical steel supports on each side, installed before a Nor'easter in 1992 to hold a three-foot-tall dam, like the one that kept out the water from Hurricane Irene in 2011. It took about five hours of construction to put up the three-foot dam across the tunnel's mouth.

But Jezycki and the carpenters were worried. Sandy was expected to be bigger than Irene: the storm was due to arrive at the same time as the high tide, which was going to be higher than normal because of a full moon. What's more, the Harlem River was not the only threat at 148th Street; water sometimes runs off the Harlem River Drive, and out of the sewers. "We've had occasion where the sewer becomes surcharged and overflows through the manholes into the yard," Jezycki says, "and flows down the track to the portal."

This article has been revised to reflect the following correction:

Correction: October 26, 2013

An earlier version of this article referred incorrectly to the area at 148th St. and Lenox Ave. where workers erected a dam in front of a tunnel entrance. It is Central Harlem, not East Harlem.