Tag Archives: flood gates

New flood gates will keep NYC road tunnels dry next time the city’s streets are under water

New York City was struck by hurricane Sandy six years ago. Since then, while the city has updated its flood-risk maps, it hasn’t taken any concrete steps to prevent storm surges from entering the city. That’s not surprising; the city is rimmed by more than 580 miles of coastline, most of it at risk from storm surge.

Map of NYC flood-zones. Image from NYC Mayor’s Office

NYC flood-zones. Image from Mayor’s Office

Instead, city planners have focused on upgrading critical systems, such as: ‘hardening’ electrical systems; relocating backup generators; flood proofing subway openings; designating more emergency shelters for flood victims. Resilience is a word the city planners like to use these days. In other words, let the seas rise, we’ll deal with the water when it comes.

the most impressive example of this approach so far has been a $64 million project (now complete) to install flood gates on two of the city’s four road tunnels, namely: the 9,117 ft. Hugh L. Carey (Brooklyn-Battery) tunnel under the East River, and the 6,414 ft. Queens-Midtown tunnel, also under the East River. Both suffered serious damage during the Sandy flooding, the Hugh L. Carey tunnel, especially  so. The portals of both tunnels are located within zone-1 (first zone to flood).

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Map showing location of tunnel flood gates

Eight steel flood gates have been installed, two at each tunnel end. The gates were manufactured by Walz & Krenzer, Inc., of Oxford CT. (“Watertight Closures for the Marine industry since 1939”), one of about 50 U.S. companies involved in the flood-control equipment business.

Each gate weighs 44,600 pounds (about 20 tons), and measures 29 ft. wide by 14 ft. high by 22 inches thick.

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MTA Photo

The gate swings on two massive hinges. When parked in its open position, the free end rests on jacks.  Assuming  a two man crew, a machine such as a forklift is needed to help close it. In the event of a storm, the crew will first remove steel cover-plates from  a trough that stretches across the mouth of the portal. Once the gate is closed, the crew will latch it to the face of the portal and to attachments within the trough. Compression seals around the gate’s inner edge will make it watertight.

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MTA photo

The only way to see these gates up close is to drive through the tunnels. You’ll get only a second or two of observation. Considering New York’s frantic traffic, stopping to gaze at the thing is something no prudent driver should attempt.

It’s just as difficult to get a good look at the gates while on foot. Barriers of one sort or another along the streets surrounding tunnel entrances inhibit pedestrians from peering over walls. The Morris Street footbridge will eventually provide a platform from which to observe the Hugh L. Carey flood gates at the tunnel’s Manhattan end, but that bridge is being renovated and will not be available for use this year.