Gaping holes in steel beams, cracked glass, rickety catwalks and rust everywhere -- that's the view from underneath D.C.'s Frederick Douglass Memorial Bridge.

The 63-year-old bridge, which carries South Capitol Street past National Park and over the Anacostia River, is slated for a $660 million replacement, and on Wednesday, District officials made the case for why it should receive the funds.

Rust holes several inches wide pockmark floor beams directly below the commuter traffic. The corrosion got so bad that officials put up signs warning trucks to stay out of the middle lane.

"The middle lane -- we should not have any trucks on it. Now enforcement is another issue," said Ronaldo "Nick" Nicholson, DDOT's chief engineer for the bridge. "That concerns me now."

Nicholson and others say the bridge is safe for the time being, but in five years, they'll need to start banning traffic from the span. D.C. Mayor Vincent Gray announced on New Year's Eve that the city would start gathering funds and bids for a new bridge -- a $660 million enterprise.

If the Douglass bridge isn't replaced, engineers say they'll need $120 million just to fix corroding beams and gaping holes in the catwalks. A 2007 paint job, which cost tens of millions of dollars, covers and slows some of the corrosion, but the bridge that was meant to last only 50 years continues to erode.

"We just keep throwing money at it," Nicholson said. "It's hard to get replacement parts. Sometimes you have to retool them, which makes it even more expensive."

The city is hoping to shave $140 million off the cost of a new bridge by dropping plans for a movable drawbridge, bringing the overall price tag down to $520 million. The Navy, which has ships at the nearby Navy Yard, has asked the city to open the bridge only twice since 2006, Nicholson said, so a drawbridge isn't really needed.

The city still needs to line up bonds and federal funds for the project, as well as a contractor. Starting in fall 2014, engineers hope to build the new bridge parallel to the old one so traffic across the river isn't interrupted.

Officials want the new bridge to be part of a larger plan to revitalize the Anacostia waterfront.

"Given the economic growth in this area, we want to make sure we have that strong crossing," Nicholson said.