To Flood-Proof Subways, N.Y. Looks At Everything From Plugs To Sheets New York City's transit authority wants to protect Lower Manhattan subway stations from storm flooding. It's racing to get technology tested and in place in time for the next big one.

To Flood-Proof Subways, N.Y. Looks At Everything From Plugs To Sheets

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How do you prevent a big hole in the ground from filling up with water when it rains? That's the challenge for much of the New York City subway system when a major storm hits, and it's the subject of today's story about urban transportation from the NPR Cities Project.

UNIDENTIFIED WOMAN #1: Becoming a world-class city.

UNIDENTIFIED MAN #1: Keep the transit system running.

UNIDENTIFIED MAN #2: We have to move people a lot more efficiently.

UNIDENTIFIED MAN #3: Come. Take a ride of the future.

MONTAGNE: It was three years ago this month that Superstorm Sandy hammered New York and overwhelmed the subway system. And it's just a matter of time before another storm like that hits. The east coast avoided one this week when Hurricane Joaquin headed out to sea. So the city is racing to get new flood-proofing technologies ready, as NPR's Joel Rose found out.

UNIDENTIFIED MAN #4: Everybody in place? Here we go.

JOEL ROSE, BYLINE: We're standing in a field in rural Delaware more than 170 miles from the New York subway. This is where engineers at the firm ILC Dover are testing something they call the Flex-Gate. It's a big sheet of waterproof fabric that's designed to cover the top of a subway entrance and keep the water out.

UNIDENTIFIED MAN #4: I don't see any water under here right now.

UNIDENTIFIED MAN #5: Might be metal.

ROSE: For this test, a Flex-Gate is sitting in a big custom-made box a few feet off the ground. The engineers cover it with several feet of water. Then, they measure how much is leaking. As the box fills up, some water starts trickling.

You're really not worried about that. That's looks like water coming out the bottom.

DAVID CADOGAN: Well, when you look at something like that - and that looks like a bit of a leak - and it's not that much when you're talking gallons per minute.

ROSE: David Cadogan is the firm's director of engineering. He says it's fine if a little water gets through as long as it's less than the subway's pumps can handle. And they can handle a lot, 13 million gallons on a typical day, even if it's not raining. Cadogan drew the first sketch for the Flex-Gate back in 2013 during a meeting with the Metropolitan Transportation Authority, or MTA, which operates the New York subway.

CADOGAN: We just quickly started thinking, well, we need to put fabric over the top. How would we seal the outside? And very quickly, we came to a very simple drawing, saying, well, this is what we think we could do.

ROSE: What did that first sketch for the MTA look like compared to this?

CADOGAN: It wasn't that far off (laughter), pretty much like a roll-up door, which is essentially what this is.

ROSE: Think of the roll-up metal doors you see over shop windows in New York City at night. Cadogan says that's partly what inspired the design. Eight months after that first meeting, ILC Dover was installing a prototype Flex-Gate in lower Manhattan. Now they're building 23 more. Cadogan says that's pretty quick.

CADOGAN: This is a solution that we designed in-house. There is nothing like this that exists.

ROSE: To get the MTA's take on the design process, I'm back in New York at the offices of John O'Grady. It's his job to make sure the subway is ready for the next big storm. After Sandy, O'Grady says, the MTA looked at other subway systems all over the world to see what worked and what didn't.

JOHN O'GRADY: And we didn't find any unique technology that we could say, someone had solved the problem. So we set about to try to see if we could research and develop technology.

ROSE: If you want to know why this problem is so hard, just look at a map of lower Manhattan. It's surrounded by water on three sides. Most of the subway lines converge here. There are six stations within blocks of each other with entrances just a few feet above sea level. And O'Grady says there are lots of different ways for floodwater to get in.

O'GRADY: In lower Manhattan here, it's actually making sure every possible entry point is closed off. So just making sure we get every vent bay, every manhole, every emergency exit, and every staircase all closed off. There is numerous different ways for flooding to occur.

ROSE: To make things even more complicated, the subway entrances themselves are all slightly different sizes. So O'Grady is looking for solutions that are easy to deploy. That's one reason he likes the Flex-Gate. It's built right into the subway entrance itself.

O'GRADY: There's an enormous effort to keep the transit system running as long as is possible up to the decision to close the system. And so this is a technology that's stored in place, and it requires a small crew to just go in there and set it up.

ROSE: No subway station suffered more damage during Sandy than this one. The new South Ferry station, which cost over $500 million to build, was destroyed by flooding. So the MTA was forced to put this older station back into service. And with rising sea levels, the risk of severe flooding is getting worse.

RADLEY HORTON: We're going to see that level of flooding, that in the past might have been a once-in-a-100-year event, happening every generation.

ROSE: I'm here with Radley Horton, a climate scientist at Columbia University. He says it's commendable that the MTA is taking this threat seriously. The agency has about $4 billion in federal money to spend on recovery and resilience. And Horton says it's important to keep track of it.

HORTON: Well, we're conducting a grand experiment. We're now seeing real money being spent to try to prepare for some of these hazards like coastal flooding. We're less far along in evaluating how these measures may work or not work.

ROSE: But one of the challenges with this stuff is you won't know it works until you see how it performs in a big - you know, in a crisis.

HORTON: That's exactly right. That's a huge issue. How can we even begin to assess whether a floodgate is working without having that big storm?


ROSE: Back in Delaware, engineers at ILC Dover are trying. They're testing out another new technology called the resilient tunnel plug. Imagine a big balloon that inflates to, well, plug up the tunnel. Engineer Jon Hinkle.

JON HINKLE: I think we're pretty happy it deployed and then took a shape that we wanted it to. But it's the first step in a long test process that we have that goes into developing anything.

ROSE: Still, engineering director Dave Cadogan says there's a real pressure to get these technologies ready for prime time.

CADOGAN: You know, we're doing everything we can to move as fast as possible because we won't have the opportunity to ask the storm not to show up.

ROSE: Cadogan says everyone on his team was very happy when Hurricane Joaquin steered away from the east coast. But he says it's a reminder that they need to get these devices in place before the next storm comes ashore.

CADOGAN: All right, gentlemen. Here we go.

ROSE: I'm Joel Rose for the NPR Cities Project.

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