Photo by wolfkann.

The 84-year-old Arlington Memorial Bridge is reaching the end of its design life. As the bridge crumbles and deteriorates at an accelerated pace, it could potentially close by 2021, according to Jenny Anzelmo-Sarles of the National Park Service.

The bridge, which spans 2,100 feet, has a $250 million price tag to stay open in the long term. The NPS has been trying to raise this funding for the past four years. But the agency's annual budget is $3 billion, and only $268 million is currently going toward transportation infrastructure.

"The National Park Service will need the support of partnerships with other federal, state, and local entities, to compete successfully for funds available from the Department of Transportation," park service director Jonathan Jarvis said in a release. "We are pursuing every funding possibility to find a path forward to repair Memorial Bridge."

Arlington Memorial Bridge facing 2021 closure w/o $250mil fix. Samples show 11in thick concrete deck is crumbling. pic.twitter.com/mbw5J89P0g — Jenny A-S NPS (@JennyASNPS) March 3, 2016

Inspection shows accelerated deterioration, indicates Memorial Bridge may close in 2021 w/o $250 million overhaul. pic.twitter.com/UNjuOTJJn5 — Jenny A-S NPS (@JennyASNPS) March 3, 2016

Last spring, the NPS had to close parts of the bridge to complete emergency repairs. Vehicles driving on the open parts of the crossing were restricted to a 10-ton load limit, eliminating most buses from traveling across the span. That limit still stands today.

The agency also moved up temporary repairs, which were supposed to start in the fall. At the time, the bridge topped the American Road & Transportation Builders Association's list of the most-traveled structurally deficient bridges in D.C. The unfortunate distinction is mostly due to the corrosion of the steel in the drawbridge portion, plus some supportive materials are missing altogether, according to the NPS.

The bridge is crossed more than 68,000 times a day. And if the drawbridge fails, there could be a six-to-eight inch drop in the roadway.

The crossing connects the Lincoln Memorial with Arlington National Cemetery and the Robert E. Lee Memorial. It was built to commemorate the reunification of the United States after the Civil War and is listed on the National Register of Historic Places.

A temporary fix is scheduled to begin next year at a cost of $5 million.