Flood plan proposed to protect Washington Mall

A rendering shows how the levee wall would look.
A rendering shows how the levee wall would look. (Courtesy Of National Park Service)
By Michael E. Ruane
Washinigton Post Staff Writer
Monday, November 15, 2010; 8:50 PM

Eighty thousand cubic yards of dirt. Thirty steel girders. An eight-foot-high concrete wall.

All to hold back floodwaters that may, or may not, surge across the Mall in the next century or so.

But in the apocalyptic, post-Hurricane Katrina world, no chances can be taken.

So government officials announced Monday morning that work is about to start on a $9 million flood control project that will alter the landscape of the Mall west of the Washington Monument to protect it, and part of Washington, from potential catastrophe.

The project will create a levee that would be erected across 17th Street below Constitution Avenue in the event of a huge flood.

It calls for the construction of large earthen berms, using tons of dirt, and the eight-foot walls on both sides of 17th Street.

It also will require engineers to sink a series of caissons 30 feet deep into the surface of 17th Street, where girders could be placed to support temporary panels to block floodwater.

Work is to begin next month and conclude next summer.

The project aims to protect large sections of downtown Washington from extensive river flooding, and to keep those sections from being declared a flood zone, which could require property owners to buy flood insurance. Such insurance runs about $1,500-a-year, officials said.

The project is the result of the Federal Emergency Management Agency's nationwide review of flood zone maps after Hurricane Katrina devastated New Orleans and parts of the Gulf Coast in 2005.

When FEMA reviewed the District's flood zones, it concluded that existing plans to use sandbags and jersey barriers to block floodwaters flowing north on 17th Street from the Potomac River and the Tidal Basin were inadequate.

FEMA foresaw a scenario in which a flood could inundate a huge crescent of downtown Washington from 17th Street and Constitution Avenue east to the Capitol and south toward Fort McNair.

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