[TallDave2]

As with most projects from that era, the environmental impact study/mitigation for such an effort today would probably cost more than the entire original project, even in real dollars, even assuming you would be allowed to build it (you probably wouldn't).

[gnarcoregrizz]

Yeah. The Hoover dam would never happen nowadays, and it has undoubtedly had some environmental effects.

Here is a fun example of how expensive infrastructure is here now:

Irvine to Corona tunnel (11.5 mile tunnel under mountains) which would connect Orange County to Riverside County: estimated 28.3 billion [1]. Both are large population centers with large economies, separated by a small-ish mountain range. They spent almost 30 million on environmental studies.

Norway made a 15 mile tunnel through the mountains for 113 million, or 0.4% of the cost. [2]

1. https://www.ocregister.com/2010/08/27/plans-for-irvine-coron...

2. https://en.wikipedia.org/wiki/L%C3%A6rdal_Tunnel

[TallDave2]

Great example... there was also an effort to expand the Tappan Zee bridge from the 1950s, adding a couple lanes was going to cost 5-10x the original iirc.

https://en.wikipedia.org/wiki/Tappan_Zee_Bridge_(1955%E2%80%...

On the plus side, we have some of the cleanest air and water any civilization has ever enjoyed, so regulation isn't all bad. Maybe the Boring Company can tunnel that out for a mere $250M.