After near-disaster, Oroville Dam spillway about to face its first big test | Hacker News Reader

After near-disaster, Oroville Dam spillway about to face its first big test

latimes.com

As the article is already 2 weeks old, in the meantime the test has been performed successfully. The problem with the old spillway was, that it was just put on top of the soil. Over the decades, the soil got eroded away by water in some places, destabilizing the spillway. The other part of the disaster, after the main spillway failed, was, that the emergency spillway basically didn't work, so they had to use the main spillway even if it was completely destroyed.

Rebuilding the main spillway was very thorough work, they removed all soil completely from the bedrock and filled the space up with concrete. On top of that they built the new spillway, up to modern standards and much thicker than the original one. There is all reason to assume that this new spillway will hold up much longer than the old one, which did work for 50 years. Also, they are completely rebuilding the emergency spillway so it can be used by adding massive amounts of concrete.

A great source for in-depth information about the failure of the old and the rebuilding effort is the blancolirio-channel on youtube (https://www.youtube.com/user/blancolirio/videos)

And Juan, the man behind the blancolirio channel, has to be the best citizen reporter out there. He sought many of the real facts and avoided the mainstream media trap of looking for blame purely to sensationalize the issue. He seems to have sound engineering knowledge, even though he is an aircraft pilot by trade. And he was able to put his plane to good use as a great viewpoint during the construction.

He has also provided wonderful interpretation on recent air incidents including the 737MAX ( he flies 777 commercially)

I'll have to check that out, I do have one question tho (maybe someone asnwerd it already somewhere?)..if everyone knew soil was underneath then wasn't this preventable ? or was it one of those..well we can't get the money to fix it until after something bad happens? I'd say it's pretty obvious soil erodes by now, and that having it underneath large structures alone is not a great idea.

It's not that straightforward; there was concrete on top of the soil, it had functioned as designed for many years.

There are problems with infrastructure maintenance at a national level, and lots of deferred maintenance/upgrades. Given that, there's no reason to suspect that upgrading the spillway prior to failure would have seemed like a higher priority than many other remediation projects. There was not an a priori way of knowing it was going to fail, instead of a bridge abutment or whatever else was presumably repaired first, and would have had to wait if the spillway work had happened first instead.

That’s right. If they’d cut down that one tree in time we probably would still have the original spillway.

> A report released in January 2018 by an independent forensic team organized by the Assn. of State Dam Safety Officials contended that the dam’s owner, the Department of Water Resources, was “significantly overconfident and complacent about the integrity of its State Water Project civil infrastructure, including dams.”

> The report found that periodic inspections of the spillway failed to identify the original design flaws and the subsequent deterioration of the spillway’s integrity.

As a side note, I watched this channels videos of the spillway failure, and then randomly a very good video of the 737-max debacle. Same guy. This is how journalism in the digital age should be done.

The new spillway may outlive the life of the containment structure its designed to protect.

I don't recall the exact figure from blanolirio's videos (I watched them all) but the new spillway has something like 10x more volume of concrete than the old one.

Video of the new spillway being used https://www.youtube.com/watch?v=EFZNUyS89fg

The end of the spillway with the enormous waterfall makes me uncomfortable since erosion back from that point working backwards along fissures to undermine the spillway basin seemed to be an aspect of design contributing to the previous failure. But presumably they have accounted for all that. It would be interesting to read the post-mortem of the previous failure and the challenging new engineering decisions behind the new design.

Fortunately the article contains such a source: https://issuu.com/asdso/docs/independent_forensic_team_repor...

At the end of the spillway the water is send upward. This is a way to dissipate the energy of the water coming down and avoid digging a hole or eroding the river itself. This appears to be a common feature in most spillways.

Here's a (pre-repair) photo of those energy dissipator blocks at the bottom of the spillway, including people for scale:

http://media.fishreports.com/reports/img-20170303-78a7bb40.j...

Hard to comprehend how massive those blocks are...

Yah, it's kind of hard to show the magnitude of the spillway and the repair work in a few pictures.

Juan (blancolirio) posed a very good time-lapse/montage (including footage from the DWR) that shows the entire repair project. The audio has comments from Keiwit's executive project director of the repair project about the insane amount of material and work that was needed.

https://www.youtube.com/watch?v=v6lus-PXS4k

Does anyone have the numbers on how much money was “saved” by not doing maintenance? Was it more or less than the $1 billion required to rebuild it?

I think in someone else's link there was a figure about the rejected 2005 improvements to the emergency spillway being $100M. I don't know if that's correct, if there would have been overruns in cost, if that's inflation adjusted, or if that would have even prevented the 2017 crisis.

I briefly looked it up, and found some information correlating this under https://en.wikipedia.org/wiki/Oroville_Dam_crisis#Timeline_o...

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