[blamazon]

Even putting costs aside it seems like it could be unlikely that such a thing could be built at all today. Flooding huge swaths of ecosystems is no longer in vogue and dam removal is picking up in pace. When was the last major scale hydroelectric dam built in USA?

Edit: looks like the information is here somewhere in the national dam inventory: https://nid.usace.army.mil/#/dams/search/&viewType=map&resul...

But I am very tired and must sleep so I will not query.

[bobthepanda]

It's worth noting that pumped hydro, and the dams that are getting torn down for environmental these days, often look very different.

Usually the dams that are getting torn down, block the entire river, and thus fish from passing up or downstream of the dam. (Fish ladders exist but are not particularly effective.)

Pumped hydro may sit by the side of a river, but otherwise not obstruct the flow, and so that is not a major issue. (Example rendering: https://cdn.forumcomm.com/dims4/default/3ac369d/2147483647/s...)

[blamazon]

Huh, that is a really important point, and totally changed my perspective on pumped storage projects. Very cool, thanks for sharing.

[lazide]

Interestingly, it’s also becoming somewhat common to dam off (concrete-fence-off?) the entire top of a hill somewhere for pumped hydro. Essentially the opposite of what you’d do for a hydropower installation.

It also makes a lot more sites interesting.

[https://www.sciencedirect.com/science/article/pii/S254243512...]

[bobthepanda]

Also, pumped storage tends to be smaller, in that it’s meant to provide a certain level of discharge for hours or days. So the reservoirs can be a lot smaller.