The rate of deterioration of the Memorial Bridge has accelerated at an alarming rate, the National Park Service says. (Astrid Riecken for The Washington Post)

The National Park Service said Wednesday that the historic but crumbling Memorial Bridge over the Potomac River may be closed to traffic in five years if it does not get a complete overhaul by then.

Without repairs, “it’s a footbridge” by 2021, said the Park Service’s director, Jonathan B. Jarvis.

The Park Service has been warning for years that the bridge has been failing. Traffic weight restrictions have been instituted, while the road surface has been patched up and the support structure shored up.

But the rate of deterioration has accelerated, and an inspection report last month by the Federal Highway Administration found conditions even more alarming, Jarvis said.

During a tour of the underside of the bridge Wednesday, Park Service officials pointed out decayed steel supports, corroded rivets, crumbling concrete and ancient, peeling paint.

The bridge shuddered as traffic rumbled overhead and the river rushed along below.

About 68,000 vehicles use the span daily, and it is believed to be one of the most deteriorated bridges­ in the country. If it closed, most of those vehicles would flood onto other crowded bridges­ across the region.

“How did it get that bad . . . is a great example of what happens when you’re under­funded to do basic maintenance,” Jarvis said in an interview. “We get annually essentially less than half of what we need to just keep even.”

“If there had been some sort of periodic maintenance . . . we might have got another 20 years out of that bridge,” he said. “Now . . . you’re facing essentially a closure of that bridge in 2021, if we don’t fix it.”

Jarvis said that the overhaul would cost about $250 million and that the repair contract has to be awarded in the next year or two to get the job done by 2021.

The Park Service has $11.9 billion in deferred maintenance projects across the country, double the amount from eight years ago, officials said.

Some of the Memorial Bridge’s eroded steel beams. (Astrid Riecken for The Washington Post)

Jarvis said he is beginning to plan for the Memorial Bridge project in the hopes that he can procure the funding. “We can’t wait,” he said.

The bridge is still safe, said Charles Borders, branch chief of the Park Service’s Denver Service Center, who is working on the project.

“It’s being held together,” he said in an interview Tuesday. “But as we see weather cycles like we’ve seen in the last two years, it’s going to get significantly worse.”

The project would include the removal of the antique drawbridge mechanism at the center of the bridge and the creation of a new central section, he said.

The mechanism includes huge steel gears, giant concrete counterweights and an ancient-looking control room with a rotary-
dial telephone on a wall.

“We haven’t gone through the design process, but [the replacement] could be a metal span, it could be a concrete span,” Jarvis said. “On top of that, the whole top [roadway] deck needs to be removed.”

The historic appearance of the bridge would be maintained. “We have to retain its historic character,” he said.

The 216-foot draw-span section has been inoperable since Feb. 28, 1961, because other low bridges on the river prevented navigation by taller ships.

The current deck has been patched here and there but still allows water to leak onto the metal structure below, promoting corrosion.

Since 2010, the Park Service has undertaken $10 million in “Band-Aid” repairs, officials said, In May, it barred heavy trucks and buses from using the bridge.

Next year, it plans to shore up the eight trunnion posts that, like table legs, support the vast weight of the drawbridge section. The shoring will take some of the weight off the rusting 80-year-old posts.

Other shoring elsewhere on the structure already has been done.

“The biggest concern was the bridge center span would drop a foot or so, not completely collapse into the river or anything, [but that] the center supports would fail,” Jarvis said. “So that’s all been shored up. But that’s a temporary fix.”

Rep. Don Beyer (D-Va.), whose district is near the bridge, said it was important for local political leaders to pitch in.

The condition of the bridge “makes it imperative for us in Congress, Democrats and Republicans, and all the local leadership, to come up with a funding plan to make sure that the reconstruction of the bridge actually happens,” he said in a telephone interview Wednesday.

The span, which is listed on the National Register of Historic Places, crosses the Potomac between the Lincoln Memorial in the District and the approach to Arlington National Cemetery in Virginia.

Designed in the 1920s by the architectural firm McKim, Mead & White, the 2,100-foot-long bridge’s central draw span was once the longest, heaviest and fastest-opening in the world.

It took one minute to open, according to a Park Service historical study.

Memorial Bridge has also served over the years as a hallowed avenue to and from Arlington National Cemetery, with countless marches, parades and processions along it.

“It’s a beautiful bridge,” Jarvis said. “To be blunt about it, I think it’s our most attractive bridge on the Potomac here. We want to certainly maintain that aesthetic.”