Quote:
Originally Posted by zilfondel
Note: not all tunnels need to be bored. The bay bridge tunnel is a series of metal tubes connected together, sunk in a narrow trench. It's supposed to be a really inexpensive way of doing things.
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This is what I want to see. If they had to, they could trench it in to retain depths for ships. Kind of a cut-and-cover on the river bed.