P3 Belle Chasse Bridge and Tunnel Replacement

Geotechnical services contribute to a unique public/private partnership.

Louisiana’s Belle Chasse Bridge and Tunnel were infamous for closures and traffic delays along LA 23. In 2022, the Louisiana Department of Transportation (LA DOTD) began building a modern long-span bridge to replace the aging bridge and tunnel. GeoEngineers provided foundation design and other geotechnical services for this ambitious project.

Although the Belle Chasse Bridge and Tunnel have carried LA 23 traffic across the Gulf Intracoastal Waterway for more than 50 years, they have been plagued by regular closings for most of that time. Northbound traffic came to a halt whenever the vertical-lift bridge opened for a passing ship, and southbound tunnel traffic had to contend with frequent flooding and maintenance closures. The tunnel leaked so much that locals dubbed it “The Carwash.”

LA DOTD planned to replace the aging infrastructure with a single 3,300-foot fixed-span bridge carrying both north and southbound traffic via four travel lanes. The $169 million project was a public-private partnership (P3) between LA DOTD and the Plenary Infrastructure Belle Chasse Consortium, a large team of consultants and contractors. It’s the first P3 of its kind in Louisiana history.


  • Foundation Design: Designing and testing foundations for a long-span bridge in soft Louisiana soil was no easy task, especially since the bridge would be supported by a combination of precast prestressed concrete piles and relatively large 48-inch diameter steel pipe piles.
  • Streamlined Dynamic Testing: Geotechnical recommendations are usually validated by on-site testing, which can cause construction delays because of the long set-up times in these soft clay soils. To streamline the process, the GeoEngineers team completed a combination of test piles and dynamic testing (PDA) to provide early-acceptance criteria for production piles. With our testing and analysis, the contractor did not need to wait for set-up to complete testing before piles could be approved.
  • Permitting and Regulatory Support: Flood-control T-walls and levees on either side of the intracoastal waterway were regulated by the United States Army Corps of Engineers (USACE). Fortunately, GeoEngineers’ staff have a lot of experience working with the USACE and navigating its regulations.
  • Slope Stability and Interaction Analysis: To satisfy USACE requirements, the team evaluated how settlement, stability, pile driving vibrations and other construction activities might affect the flood walls.


The GeoEngineers team’s creativity streamlined foundation testing and helped to keep the project on schedule. Although GeoEngineers’ work is complete except for ongoing construction observation, construction on the new bridge is expected to continue through 2024.

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