A historic bridge that connects downtown Birmingham to Southside will be replaced soon.

The 21st Street (Richard Arrington Jr. Boulevard) viaduct between 1st Avenue North and 1st Avenue South and over the Norfolk Southern and CSX Railroad is at the end of its lifespan and needs to be replaced, according to the Birmingham Department of Planning, Engineering and Permits.

The bridge, also called the Rainbow Viaduct, is currently load restricted and signed "No Trucks," according to the department.

Originally constructed in 1918, the bridge was formally dedicated to the decorated veterans of the 167th Infantry Regiment. They fought as part of the "Rainbow Division" during World War I.

The Birmingham City Council this week approved entering into an agreement with the Alabama Department of Transportation to utilize 80 percent federal funding in the design of the bridge replacement.

The preliminary engineering is estimated to cost $800,000. The city will pay $160,000 out of the total cost.

"There will be a public engagement process to look at options for how the new bridge will look," said Chanda Temple, public information officer for the Birmingham mayor's office. "It will be built back in a way that captures the historical significance."

The design phase will take about 12 months.

That means the construction of the 21st Street bridge will take place after the replacement of the downtown Central Business District bridges on Interstate 59/20.

Those bridges are expected to close this fall. They will be removed and replaced over a course of 14 months.