Waterproofing the NYC subway system is an important part of the city’s efforts to become more climate-resilient and prepare for future Superstorm Sandy-type flooding as global warming increases extreme weather events. To prevent another situation similar to the flooding of the South Ferry subway station, which is still under reconstruction, and the flooding of nine tunnels that will shut down the L train for 18 months in 2019, the Metropolitan Transit Authority is spending $4 billion in mostly federal disaster relief funds to repair and harden its transportation infrastructure. That includes testing innovative solutions such as flexible covers and tunnel plugs that could keep the city’s subway system dry during flooding events.

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The city has partnered with product engineering firm ILC Dover to begin installing Flex-Gate — a sheet of waterproof fabric that is placed in a container perpendicular to subway entrance railings. In a major flood event, the Flex-Gate quickly unspools to cover subway entrances. Flex-Gates have been installed in 14 subway station entrances around the city and by the end of the year, another 50 should be installed. A larger version, called Portal Flex-Gate, could soon be in place at rail and vehicle tunnels such as the Brooklyn Battery and Queens-Midtown, ready within minutes to seal tunnels from rushing water.

Related: NYC unveils plans for redesigned “accordion” subway cars and renovated stations

The MTA is also testing another ILC Dover product, called a resilient tunnel plug. The technology looks like an inflatable balloon and acts like a durable dam that can quickly plug up a tunnel. The technology expands from a container on the wall to plug up the tunnel, preventing water and also potentially smoke and gas in case of a terrorist attack or electrical malfunction.

But stairways and tunnels aren’t the only way water can penetrate the system. There are an estimated 5,600 street-level openings across the city. The transit agency is currently waterproofing about 450 manholes and testing solutions for covering thousands of street-level vents.

+ MTA

+ ILC Dover

Via City Lab

Images via MTA and ILC Dover