Natural Hazards News

Engineering Climate Change Resilience into New York Subways

Impending renovations presented at a conference on transportation systems and climate extremes would keep hurricane-driven waters out of subsurface transit tunnels.

By Sam Lemonick

New York City doesn’t want to relive Hurricane Sandy, and officials know it’s only a matter of time until another big storm hits. The city’s subway authority is making plans to fortify buildings to prevent a repeat of flooding that crippled the system in 2012. An engineer described some of those retrofitting plans at a first-of-its-kind meeting this week on the resilience of transportation systems in the face of climate change.

Sandy struck New York City in October 2012 with winds blowing 75 miles per hour (120 kilometers per hour). Some parts of New York City saw almost 14 feet (4.2 meters) of flooding as the storm pushed water inland. The hurricane killed 285 people from the Caribbean to New England, 49 of them in New York.

During those chaotic hours, water poured down into the subway tunnels that connect Manhattan to Brooklyn, Queens, and the other boroughs of the city. Seven tunnels under the East River flooded, closing subway lines for days. One tunnel was closed for more than a year as it underwent $250 million in repairs.

Batten Down the Fan Plants

Hoping to avoid a repeat of that destruction, New York’s Metropolitan Transportation Authority (MTA) hired the engineering firm Arup to retrofit buildings called fan plants. These provide ventilation for the underground rail system but also gave Sandy-driven water a way to reach tunnels.

Now the plans for those renovations are done, and this week, Tim Savery, an engineer with Arup in Edison, N.J., who worked on the designs, described the project at a conference in Washington, D.C.

The meeting, organized by the Transportation Research Board, an arm of the U.S. National Academies of Sciences, Engineering, and Medicine, brought together an international mix of engineers, researchers, and government officials to talk about adapting transportation infrastructure for extreme weather and a changing climate.

Planning for future weather was the biggest topic of discussion at the gathering. Engineers and infrastructure planners are increasingly turning to climate modelers to ensure that their designs will withstand extreme weather in coming years. And climate researchers are fine-tuning their models and learning how to adjust them to inform those decisions better.

Air Yes, Water No

Fan plants blow fresh air into subway tunnels while removing exhaust. They’re built over air shafts leading from the surface to the tunnels below, which can be as deep as 180 feet (55 meters) below the surface. The fan plants have vents to allow air in and out—through which Sandy’s storm surge entered the tunnels below.

The MTA included fan plants in a 2013 announcement of its intention to refit subway stations and other parts of the system.

Most of New York’s fan plants saw only about a foot (30 centimeters) of flooding during Sandy, although even that was enough to send water down into the train tunnels. Per MTA’s orders, however, Arup engineers have designed retrofits for the sites to keep out water 12 times that deep. Protection against 12 feet (4 meters) of flooding should accommodate the storm surge from a category 2 hurricane, plus offer a 3-foot (1-meter) margin of additional protection. Sandy was rated as a category 1 storm when it reached New York.

Case-by-Case Corrections

Savery explained that his group created different solutions for each plant. In the worst case, at least one of the plants would be completely submerged. At that site, floating gates will automatically lift to cover air vents as waters rise.

At another, engineers designed a wall 12 feet (4 meters) high to surround the building, with doors that can withstand the pressure of a flood. At that location, the group also plans to tie the building down lest it float away during a storm because parts of it aren’t anchored to the air shaft below.

Redundant systems and additional lines of defense will make flooding even less likely, Savery said, adding that work at the fan plants could start next summer.

Focusing on individual structures is just one way to approach the problem of storm surges, according to Mathew Mampara, an engineer with the firm Dewberry, which is based in Fairfax, Va. But he says more expansive solutions—like flood gates that could close New York harbor completely—require money and support that isn’t readily available.

“Until there is political will and resource allocation for larger projects, an asset-specific approach makes sense and is what we have to do,” Mampara says.

—Sam Lemonick, Freelance Science Journalist, email: [email protected]

Citation: Lemonick, S. (2015), Engineering climate change resilience into New York subways, Eos, 96, doi:1o.1029/2015EO035875. Published on 18 September 2015.

© 2015. The authors. CC BY-NC 3.0