National Mall floodgate may face 1st test if Irma East Coast path holds

We still don't know how Irma will affect us in the DC area. We wanted to know, are the floodgates ready here?

WASHINGTON (WUSA9) - After Hurricane Katrina brought the Crescent City to its knees and floodwaters filled the basement of the National Archives in Washington only months later, authorities in the nation’s capital came up with a solution to shield national treasures from Potomac storm surge.

The Army Corps of Engineers built a stone, steel and concrete wall 10 feet tall at its highest point, visible from the Washington Monument and World War II Memorial. It crosses 17th Street N.W., the heart of the National Mall.

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The area packed with tourists is also one of the District’s most vulnerable flood points.

“We can have this levee ready in three hours,” said National Park Service spokesman Mike Litterst in an interview Wednesday. “There are flatbed trucks at the ready 24/7, with pieces of the barrier that cross the street, ready to install.”

The design was selected to protect the city’s downtown core, but if the levee is raised, water will in fact be retained within a sizeable portion of the Mall.

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The wall is comprised of three sections: Two dark grey stone portions on each side of 17th Street, and a removable aluminum middle, only present when waters approach the limits of the city’s 100-year flood plain near Federal Triangle.

In the event of a major flood, steel beams rise from the sidewalk and roadway, where concrete blocks can be moved into place. The removable concrete section join the two stone walls, blocking the roadway and holding back millions of gallons of water – if need be.

“We test our ability to raise the levee each year and it’s ready to go if Irma holds its path,” Litterst said. “But the levee hasn’t been tested by mother nature yet. We’ve never had to use it yet for a major flood since we built it.”

Forecasters shifted the projected path of Hurricane Irma eastward early Wednesday, with some models bringing the hurricane’s trajectory parallel to the Eastern Seaboard. A double U.S. mainland landfall is also possible, first in Florida, then South Carolina.

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The Army Corps of Engineers will make the call if or when to raise the levee, with oversight and maintenance completed by the National Park Service.

“Bottom line, the message is that if we need to protect Downtown from large scale flooding, we’re ready,” Litterst said. “We’re confident this will get the job done, and the wall, can be ready on the Mall.”

© 2017 WUSA-TV


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