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Comment by chrishacken | Hacker News Reader

It's not just flowing over the top of the dam; the water is channeled through an area designed to handle overflow; but the channel is damaged.

See pic: http://s4.reutersmedia.net/resources/r/?m=02&d=20170213&t=2&...

I believe they're worried about the erosion tearing apart the hillside and thus destabilizing the entire hill; at which point the whole hill would just collapse.

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LA Times has more great photos.

Google "Major sinkhole on spillway at Lake Oroville" to avoid the paywall.

http://www.latimes.com/visuals/photography/la-me-lake-orovil...

What I've been wondering is: What, if anything, did they do during all of these years of drought in order to ensure dams and all required mechanism remained sound and ready for when rains returned?

The lake near my house was down 120 feet. You could see land and structures never seen in decades. Prime opportunity to get in there to inspect and maintain said infrastructure. Not sure anything was done at all.

I am no expert in concrete but I would like to think the break in the Oroville spillway could have been detected and dealt with with cursory inspections over the last several years, when access was easy due to the drought.

I don't like it when folks are put in danger because other folks who are supposed to be working for us don't do their jobs. Not saying this is what's happening here, I don't know, but the question needs to be asked.

The spillway can be completely shut during normal operation of the dam. So the drought didn't provide any increased opportunity to do inspections.

It did in the sense that you could undertake projects that would be impossible had the lake been full. In other words, you had certainty of not needing the spillway for months/years.

It's pretty impossible to predict that the spillway won't be needed in a given wet season.

They share the data about the level of the reservoir:

http://cdec.water.ca.gov/histPlot/DataPlotter.jsp?staid=ORO&...

The wet season last year basically filled the reservoir up from its lowest levels. So a project started in the middle of 2014 would need to leave the system operable by December, and they have that same ~6 month period in pretty much every year.

The point is they had 6 to 10 years (however long the drought lasted) to get ready for this moment in time, even if a little bit at a time.

Nobody ever seems to do this. We always wait for disasters before fixing or maintaining anything. This, despite the fact that we pay taxes, plenty of taxes, to fully staff, train and employ departments with thousands of people who are supposed to actively be looking after these things.

It's the infrastructure equivalent of a sysadmin who never looks after security and then, when all hell breaks loose, proclaims we need to do something about security.

Sure, but my point is that they have the same opportunity to do inspection whether there is a drought or not. So they've had the lifetime of the dam to do inspections and maintenance, not just a few years.

There's lots of possibilities. Maybe they didn't do inspections last year. Maybe they did inspections and noted damage that did not yet warrant repair. Maybe they did inspections and missed damage. Maybe they were unable to secure funds to repair the damage. Maybe the damage was noted too late to do repairs last fall. Etc.

The thing to do is wait and see if they come forward with a reasonable explanation of what went wrong and then feed that information into the maintenance plans at this dam and others.

It's easy to say this after the fact, but infrastructure like that has a minimal budget for that sort of stuff. If we did this on every dam in the US, it would potentially amount to a billion dollars or more. At a time when the government is trying to claw back budgets, that sort of thing is never going to be approved.

Generally sink holes like what is affecting the spillway are caused by rain and flooding. So I'd say it is likely that the inspections all came up clear for the past X years, then the rain started, the sinkhole formed and the reservoir started filling at the same time.

What's interesting is that you know this. Which means that others should as well. Which means that, I don't know, perhaps modelling what might happen as rains returned, even conducting some tests with tankers full of water could be considered a prudent idea.

In other words, the idea that things could go bad once lots of water came back isn't a far-fetched concept. Yet we are reactionary. We don't seem to spend any time a-priory to try and get ready for such events. History is full of such fuck-ups.

Like I said in my other response; it comes down to money. If we took every "what-if" into account, we'd be wasting trillions of dollars each year on hypothetical scenarios.

This was the first time the spillway was EVER used in its existence; for all we knew at the time, it would have never been used.

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