Oroville Dam in California is F.U.B.A.R.-ed.
Here's an actual knows his stuff engineer commenting : http://www.sacbee.com/news/local/article132356269.html
Basically there's a quadruple failure going on.
"The Dam part of The Dam" is fine, as is the mountain and the bedrock.
The normal power generator section is jammed by debris.
The Main Spillway has that lovely plume from the new channel.
As horrible as it looks, they had to send 100,000 cfs into it to save the Emergency spillway, and it held, it just looks really bad.
The "auxiliary"=emergency spillway eroded UP the hill, right up to the concrete pad top at 2 points.
They're sending loaded mining trucks to the 1 worst part of the concrete pad.
They aren't saying they'd rather fix the other 1 first, because it doesn't matter ... they can't reach it.
White Knuckling it time for this first week with 6-8 inches of rain (and some snow) on the way.
They aren't saying it'll hold for the spring melt season.
They're clearing main spillway debris out from the powerplant outlet.
It looks like they think they're rebuilding it, not just the emergency hold your breath stuff.
"Weathered Bedrock" that wasn't weathered when they built the dam, seems to be the biggest problem.
Metabunk has a long but decent thread of details, with very solid and quick moderating.https://www.metabunk.org/
(edit see better link below)
(edit on 2-16)
Here's what they're doing as of 2-17 (edit see better link below)https://www.metabunk.org/oroville-dam-spillway-failure.t8381/page-22#post-201036
2-20 edit , Metabunk has a collected details thread now :https://www.metabunk.org/oroville-dam-spillway-thread-quick-links.t8416/
Construction started in '61, but late 60s Geology discovered some things about Volcanic rock, that allows a "hammering" of bedrock seams.