New Yorkers in Exile

[BullNBear52]

Hurricane Exposed Flaws in Protection of Tunnels

By ELISABETH ROSENTHAL


Nearly two weeks after Hurricane Sandy struck, the vital arteries that bring cars, trucks and subways into New York City’s transportation network have recovered, with one major exception: the Brooklyn-Battery Tunnel remains closed.

The devastation there has underscored how major tunnels across the region are poorly protected from extreme weather and how they will need significant modifications to prevent such catastrophic failures in the future.

The tunnel’s general manager, Marc Mende, recounting what happened on the night of the storm, made it clear that he had no ability to block the angry rapids he saw heading for the Manhattan entrance.

He described the scene as “surreal,” saying that he had quickly helped power down a generator and then made a harrowing drive through the nearly two-mile-long tunnel as it started filling with water to make sure his workers had evacuated.

“I couldn’t believe it — this tunnel never flooded before,” he said. “This tunnel didn’t even get puddles.”

Unlike a number of other tunnels around the world, the Brooklyn-Battery does not have even a basic system to block water at its entrances. No gates or plugs or other barriers. Nor do Manhattan’s other tunnels. Defenseless under the storm’s ravages, the Brooklyn-Battery instead served as a drain for Lower Manhattan, filling with nearly 100 million gallons of water.

It is unclear when the tunnel is going to reopen, since engineers are just beginning to assess the damage to lighting and ventilation systems, for example. That leaves the 50,000 vehicles that used to take it each day — from commuter express buses to cement trucks bound for the World Trade Center site — still struggling to find alternatives.

“I’d guess now over the next few years, we’ll see more being done to identify critical facilities and protect them from extreme events,” said D. Wayne Klotz, past president of the American Society of Civil Engineers and a Houston water engineer. “If you think what happened is unacceptable — and I’d say it was — you have to do something. Because I can guarantee you this kind of storm will happen again.”

In interviews, several engineers said they were shocked that New York City had not done far more to safeguard its tunnels, especially the Brooklyn-Battery, the longest underwater tunnel in the United States, which has a notoriously low-lying entrance.

While the rising seas and extreme weather associated with climate change have raised the risk, engineers also point out that because tunnels have a limited number of entrances and exits, they are not that hard to protect.

After a close call during Hurricane Katrina, Mobile, Ala., rejiggered the ventilation system of a major tunnel to prevent damage from floodwater; the city has studied building up ground around entrances.

Houston has installed watertight doors to protect its pedestrian tunnels from floodwater — much like the sealing emergency doors on cruise ships. The Midtown Tunnel in Norfolk, Virginia, has long had a floodgate, which is tested twice a year.

Richard Dawson, director of the Center for Earth Systems Engineering Research at Newcastle University in England, said he “was quite surprised there weren’t floodgates” on New York’s road and subway tunnels. Many stations of the London Underground have them.

In recognition of the growing risk, the Department of Homeland Security in January successfully tested a giant protective inflatable tunnel plug that expands in minutes when filled with water, like a car air bag. Before Hurricane Sandy, the Metropolitan Transportation Authority deployed considerably less sophisticated methods, using plywood to cover some subway grates and piling sandbags at entrances.

Asked whether the Transportation Authority was exploring new flood-prevention measures, Aaron Donovan, an agency spokesman, said: “At this point, our focus is on the immediate need to restore the tunnel. Long-term planning can and will take place once this is behind us.”

The Brooklyn-Battery Tunnel had never closed for weather, even as a precaution, until Tropical Storm Irene last year.

But water levels on the southern end of Manhattan have risen about nine inches since the Brooklyn-Battery Tunnel was opened in 1940. It is a significant increase, since its entrance is just a few feet above sea level.

The Queen-Midtown and Holland Tunnels also flooded, though less severely, during Hurricane Sandy. Both have now reopened.

“I always knew Manhattan’s tunnels could flood,” said Scott Douglass, a coastal engineer at the University of South Alabama. “But a computer model is a lot different than seeing pictures with water pouring in.”

Building codes and engineering practices meant to protect urban infrastructure from weather-related disasters have generally not kept pace with evolving scientific knowledge, computer-assisted engineering capabilities and a shifting climate, experts said. The problem is amplified for older structures like the Brooklyn-Battery Tunnel.

“They were using slide rules to crunch numbers,” said Mr. Klotz, and relying on limited historical weather data to define a worst-case flood. New computer modeling provides guidance and solutions. After one of its coastal plants narrowly escaped flooding during Hurricane Ivan in 2004, Chevron asked Dr. Douglass to model its vulnerability. The result was an 18 foot-high sea wall that prevented damage during Hurricane Katrina.

The same model estimated a storm surge could be nearly 30 feet at another Gulf location, Dr. Douglass said, adding: “People say that couldn’t happen. But yes it could. That is what we should be doing now in every coastal city.”

Rob Beck, senior vice president of engineering at Munich Re, the global insurer, said that when asked to insure tunnels, he studies the elevation of the entrances relative to severe floodwaters. “This is an extreme event in terms of urban infrastructure, but the event was predictable and known — I knew if it hit at a certain time, the subways were flooded,” he said. “The M.T.A.’s tunnels were never designed for this kind of storm surge. Should they be? In my opinion: clearly yes.”

But protection can be costly and cities tend to respond only after disasters. Houston installed the watertight doors in its pedestrian tunnels only after flooding caused extensive damage during record rainfall from Tropical Storm Alison in 2001.

“We’ll save hundreds of millions by closing half a dozen doors,” said Mr. Klotz, the past president of the engineers’ society. “It was amazing how little they had to do.”

Asked what would happen if a similar storm hit again, Mr. Mende, the manager of the Brooklyn-Battery Tunnel, shook his head, calling Hurricane Sandy “an act of God,” as pumps whirred on the barren toll plaza in Red Hook the background.

He said he was proud of his maintenance staff’s work in response to the disaster. While engineers said the flooding could have been readily prevented,

Mr. Klotz said: “Whoever owns that tunnel knows exactly what it would take to keep water out in case of a flood. and it’s not high tech. They just didn’t want to spend the money.”


http://www.nytimes.com/2012/11/10/nyregion/hurricane-sandy-showed-vulnerability-of-citys-tunnels.html?ref=nyregion&pagewanted=print