Check out the Belle Chasse Tunnel and Judge Perez Bridge on LA 23 over the Algiers Canal in Plaquemines Parish, Louisiana, while you still have the chance.
https://www.gribblenation.org/2020/01/belle-chasse-tunnel-and-judge-perez.html (https://www.gribblenation.org/2020/01/belle-chasse-tunnel-and-judge-perez.html)
There is a place to replace the crossing starting in 2021 with a new toll bridge expected to open in 2024. It will be Louisiana's first public-private partnership, with $162 million in funds having been approved for the project.
https://www.theadvocate.com/baton_rouge/news/politics/article_3ca4405e-210a-11ea-854a-ff39127e6e33.html (https://www.theadvocate.com/baton_rouge/news/politics/article_3ca4405e-210a-11ea-854a-ff39127e6e33.html)
From the pix, I'm guessing that the tunnel was rendered impassible for quite some time during and after the Katrina disaster/debacle. A bridge would, of course, obviate this problem -- and it's not surprising it took 14+ years to identify the funds and funding method to effect the fix, considering all the other projects required to repair various damage in and around the region.
Will they seal the tunnel, or make inprovements to it and use it as a toll-free bypass for locals?
Great video.