A draft flood-control plan presented yesterday by the National Capital Planning Commission (NCPC) calls on the federal and D.C. governments to build new stormwater facilities to avoid the kind of flooding that damaged downtown buildings last summer.
The “ancient” sewer system for handling stormwater runoff in the District makes more flooding of the Federal Triangle area around the National Mall nearly unavoidable, said NCPC Chairman John V. Cogbill.
The District was built on a flat area at the confluence of the Potomac and Anacostia Rivers, leaving almost no natural barriers against high waters.
Measures mentioned by NCPC include higher levees along the river banks near the National Mall and a pumping station to pump rising waters away from federal buildings.
The NCPC’s draft plan cites an Army Corps of Engineers report saying a $7 million investment in levees to protect the National Mall could prevent $200 million in damage to office buildings, museums and memorials.
The District’s sewer system needs to be expanded to handle more water, Mr. Cogbill told about 70 representatives of federal and D.C. agencies during a meeting at the Ronald Reagan Building and International Trade Center.
“We know that this is going to be an expensive problem,” he said.
The plan so far has focused on a $1.9 billion improvement of the sewer system over 20 years. It would include separate pipes for sewage and stormwater so that flooding would not force sewage into the streets.
The draft plan says the kind of development that has been going up along Constitution Avenue Northwest for decades leaves floodwater nowhere else to go but inside buildings. Cement has replaced the grass, plants and soil that would normally absorb the water.
Building owners who pump water out of their basements can make the problem worse by dumping it into streets or gutters where it overflows into other buildings.
“We can’t do this on a piecemeal basis,” Mr. Cogbill said.
The NCPC and D.C. Council were spurred to action by flooding in the last week of June 2006 that forced the closing of the Internal Revenue Service headquarters, the Commerce Department, the Justice Department, the National Archives and several Smithsonian museums. More than seven inches of rain fell on the District on June 25 and June 26.
The IRS headquarters sustained the worst damage. Floodwaters overflowed a moat around the building into the basement, where maintenance equipment and electrical transformers were damaged or destroyed under 20 feet of water.
The draft plan merely discusses the extent of the District’s shortcomings for preventing flood damage and a few options for improvement. Federal and D.C. agencies are supposed to develop more specific plans on their own.
The General Services Administration (GSA), Homeland Security Department, the National Park Service, FBI, IRS, Justice Department and D.C. Water and Sewer Authority all had representatives at the meeting.