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
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