You wouldn't do it that way. You would have several 10 foot diameter pipes (which they already make, and are small enough to fit on a truck). That way when one pipe has a problem you can shut it off an still get most of your flow. A lot more expensive than an open canal though.
Congratulations for their stunt. That doesn't mean anyone else should follow that though. There are lots of disadvantages to large tunnels and large pipes and so I would still recommend for most that a different path should be taken.
As an engineer and expert on this though, I'm not an expert. I've looked into it just enough to know that I would expect that it would just not be worth it, but maybe I'm wrong for your case
That is my entire point. Even with many smaller pipes it has not been worth it. A big trench is just more affordable and covering it is probably a better option than replacing it.
