Three years after Hurricane Sandy brought storm surges that flooded some of New York City's subways, the city has begun installing devices at train station entrances designed to keep water from entering the system during future such weather events.

The Canal Street Station, which serves New York's Chinatown district, is the first station to be equipped with ILC Dover's Stairwell Flex-Gate. The metal-framed fabric closure can be deployed automatically or manually in less than five minutes. The device is designed to protect stairwells from storm surges of up to 14 feet, levels comparable to those that hit Lower Manhattan at the height of Hurricane Sandy.

Flex-Gate functions similarly to a roll-up storefront security door. It resides in a container and is pulled across the opening of a subway stairwell if flooding is anticipated. The flexible cover travels in guides during deployment and seals against them when challenged with water. Manual deployment can be carried out by one person, even during most high winds.

The Stairwell Flex-Gate is a metal-framed fabric closure designed to protect subway stairwells from storm surges of up to 14 feet. Image credit: ILC Dover.According to its manufacturer, the design has been tested against a 16-foot water head pressure and is scalable to water levels up to 30 feet. The company expects that some water will penetrate the cover, and so intends it to be used along with the subway system's existing water-pumping technologies.

Much of New York City, and Lower Manhattan in particular, sits less than 20 feet above sea level. Hurricane Sandy hit during a full moon when tides ran higher than normal. The hurricane's 14-foot storm surge shut the system for two days while it was pumped out. New York's Metropolitan Transportation Authority estimated the damage to its infrastructure at almost $5 billion. The city plans to cover an additional 23 stairwells around Lower Manhattan with the Flex-Gate.