The state plans to replace the Belle Chasse tunnel as part of a $122 million project that would include private dollars, Louisiana's transportation chief announced Wednesday.

Replacement of the tunnel, which opened in 1956, and the nearby movable bridge, which opened in the 1960's, would be financed through a public-private partnership, federal dollars and toll revenue, said Shawn Wilson, secretary for the state Department of Transportation and Development.

"What you have is a way to bring real dollars to the table, to address a real need for replacing a bridge and a tunnel," he said in an interview.

Wilson made the announcement to a noontime address Wednesday to the Plaquemines Association of Business and Industry in Belle Chasse.

The tunnel, on La. 23 and used by about 30,000 motorists per day, is seen as a choke point for those entering the parish.

The tunnel and bridge have had flood problems, and the state spends about $500,000 per year to maintain them.

Replacing it has been discussed for years, and Gov. John Bel Edwards has said the project is a key priority for economic growth on the West Bank of the Mississippi River.

The two-lane tunnel handles southbound traffic and the bridge is for motorists heading north.

Public-private partnerships are known as P3s in state government circles.

The announcement marks the first time the state has solicited one.

Under the arrangement, private firms do the building in exchange for a longtime revenue stream.

Firms can make a profit of 10 percent or more through yearly payouts.

Wilson said he hopes that up to $50 million of the work can be financed through a federal program called the Infrastructure For Rebuilding AMERICA Grant.

Most of the rest would be paid through tolls, and possibly local contributions or state dollars.

Wilson said tolls will be as low as possible "but at the end of the day infrastructure costs."

Asking the state or federal government to pay for the project, he said, "is just not going to happen."

Earlier this year a Wilson-backed push to increase the state gasoline tax by about $500 million per year died in the Legislature without a floor vote in either chamber.

The action likely killed any chance for a major boost in state aid for roads and bridges until at least 2021 because of legislative rules and political concerns.

Louisiana has a $13 billion backlog of road and bridge needs.

"We are trying to figure out ways that we can deliver a structure," Wilson said.

Wilson announced in January that the state was gauging interest from major firms about teaming with the state on high-profile projects in the Baton Rouge area and elsewhere.

The latest plan is different from a failed, P3 proposal unveiled in 2015 by the worldwide engineering firm AECOM.

The idea was to build an $800 million "inner loop" in Baton Rouge, called BUMP, through a public-private partnership.

However, that plan was initiated by AECOM, not the state.

A state panel killed the proposal amid cost concerns.

Edwards, Senate President John Alario, R-Westwego, House Transportation Committee Chairman Kenny Havard, R-St. Francisville and Senate Transportation Committee Chairman Page Cortez, R-Lafayette are among the state officials briefed on the plan.

DOTD officials hope to present the proposal to the House-Senate transportation committees soon.

Follow Will Sentell on Twitter, @WillSentell.