BayouManchac

One of East Baton Rouge Parish's three historic bridges listed in 'Crossing the Bayou: Louisiana's Historic Bridges,' the span over Bayou Manchac on La. 73 is a pony truss style. It was built in 1931. The three Warren truss spans, made of diagonal braces, withstand several different types of force, including high winds. These types of truss bridges are also lightweight and require fewer materials than other types of construction.

Construction is expected to start Monday on a nearly $10 million project to replace three aged bridges that cross bayous under Airline Highway in Ascension and East Baton Rouge parishes.

The more-than-yearlong project will replace both bridges over Bayou Manchac at the Ascension-East Baton Rouge parish line and also, 1½ miles to the southeast, the southbound bridge over Bayou Francois in Gonzales, a state highway department spokeswoman said.

State highway officials said they don't anticipate any closures on Monday but drivers should expect to see crane operations on the southwest end of the Manchac bridges to install test piles.

The Manchac bridges are near the State Fairgrounds, which is BREC's Airline Highway Park, in Baton Rouge.

All three bridges on Airline, which is also known as U.S. 61, were built in the early 1950s.

"Being 60 (-plus) years old, they have reached their expected design life for bridge structures constructed at that time," Brandie Richardson, the state Department of Transportation and Development spokeswoman, wrote in an email Friday.

Richardson added that the bridges are not in failing condition at the present time, despite their age, but DOTD is moving to replace them before they get to that point.

She said DOTD identifies as priorities for replacement or repair those bridges with traffic weight postings that are also part of the National Highway System.

"U.S. 61 is part of the NHS and is a heavily-used truck route," Richardson said.

James Construction Group was awarded the $9.96 million job, Richardson said. The work isn't expected to be finished until late 2020 and drivers should watch for future updates.

Email David J. Mitchell at dmitchell@theadvocate.com

Follow David J. Mitchell on Twitter, @NewsieDave.