Quote Originally Posted by douglasm View Post
I doubt if they would raise the roof of the tunnel, except maybe to notch it for containers. What is more likely is that they would lower the floor, like BNSF did for the Cascade Tunnel a number of years ago. Dropping the floor wouldn't cause structural problems raising the roof would.
If I remember correctly, they did this about 20 years ago now. But they were not able to get it as large as the Port Huron tunnel --- don't know why. But they did it to make it handle much more traffic that it could before the change.

Look at the bottom of the entrances.