I looked for more information about this situation. LAT has a live blog that seems to have some really good info about the dam, the spillways, and the damage in the early posts to the live blog http://www.latimes.com/local/california/la-live-updates-orov...
The main spillway is out of action due to major erosion damage in its concrete flume. The power plant is shut down because the water level at the low end, in the diversion pool, is too high. So the two normal ways of releasing water are out of service. The emergency spillway is just a dirt hill near the dam with a concrete lip at the top.
There's a data feed from sensors at the dam.[1] "Level" is probably good data. "Out" flow rate may not be meaningful; the emergency spillway probably lacks a flow meter. Here's a plot of "Level".[2] When it's below 900, the auxiliary spillway should stop flowing. As of 2330, it's at 900 feet almost exactly.
The main spillway was open last night, carrying 100,000 cu ft/s of water (comparable to Niagara Falls). I guess it is still open, but I only spent a minute trying to find a current source.
They had reduced the main spillway flow prior to water starting to flow out the emergency spillway, but they increased it after that happened.
edit: it seems that the water level is below the emergency spillway now, but the main spillway is still open, probably at least partly out of concern about coming rain.
The video clearly shows the over-topping of the emergency spillway and the flooding/over-topping of the recreational area.
It also shows the main spillway and the damage is obvious, particularly at the 22 minute mark.
It's actually surprising how bad the damage is to the main spillway, it's not just a 'sink-hole' as was earlier described, it appears totally destroyed across a large portion of the middle part causing severe erosion of the land underneath and water spilling to the left side as well as rebounding up and over to the remaining lower section.
This video shows the damage to the main spillway even more clearly:
Currently there are 100,000 cfs flowing down the main spillway. That's how they dropped the level of the Lake so quickly. But, you are correct that the main spillway is heavily damaged, but they are still using it because they don't have another choice and there is more rain on the way.
no, they only close it for short periods of time during visual inspection of the damage, the electric part is completely out of service, the spillways are the only drains currently.
edit: it should be noted that the main spillway damage in itself doesn't threaten the hill and the lake, the issue is fragments or rocks and concrete sent downstream, that might partially clog the river or destroy some infrastructure.
Overflow means the actual spilling over the top (the emergency spillway) on to hill and street below? So we still have the broken main spillway in action or not?
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.
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.
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.
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.
I should have used a different term, for clarity. By overflow I meant that the estimated amount of water in the reservoir exceeded its total storage capacity and they had to use spillways to drain the excess. We have a geo engineer on our team and he's saying that while primary spillways are made of concrete, the secondary (emergency) spillways are made of soil and materials and can deteriorate quickly.
Overflow over the top of a dam this size and type will almost certainly result in complete structural failure. The overflow we've seen so far is a secondary canal diverting excess water away from the main dam.
Is there an article discussing the dangers of continuing to use the main or emergency spillways? I'm not clear on why the downstream destruction is so dangerous. (And I apologize if it's completely obvious, maybe I'm just dense on this.)
California's damming of the Sierras and construction of the aquifers were primarily about flood control. Supporting the growing population came secondary (that's the easy part). An enormous effort was put into diverting melting snowpack into mountain valleys. This essentially created the northern and middle parts of the Central Valley, on top of creating sustainable year-round sources of fresh water for the developing coastal cities.
Downstream destruction is of concern because that entire region depends on flood control. The habitability and agricultural production of the corridor between Oroville and Sacramento relies upon, and was created by, the flood control of Plumas, Yolo, Butte, etc counties. There are a number of canals, diversions, and reservoirs both above and below the Oroville to further control flow the dam as it reaches our rivers. However, most of the re-routing is also man-made and thus untested for such an event.
Dirt hillsides are not designed to have 100,000 cubic feet of water rolling down them. They tend to erode extremely quickly and can quickly turn into uncontrolable discharges if the lip erodes.
For the main service spillway, the main concern is that the flow of water will cause erosion damage upstream of the existing damaged site[1]. If the damage to the concrete continues up the spillway to the top, it could render the spillway inoperable.
For the emergency spillway, the main concern is that a continued flow of water would erode the soil off the hill to the point that the hill would no longer support the spillway (the concrete lip at the top of the hill). If this happened, the spillway would fail. The effect wouldn't be as severe as if the dam failed (because there would still be a large hill in between the water and where it wants to flow), but the erosion along the path of the water would get out of control pretty quickly.
The spillway is damaged and eroding as water flows through it. As it erodes it opens up such that more water can flow, accelerating the erosion to the point where the entire hillside erodes away and the dam essentially fails.
I can understand those concepts just fine, but when I look at the dam in Google Maps, it is not clear to me how this is specifically going to occur. The main spillway is on the hillside next to the dam, and the emergency spillway is on the same hill, yet further from the dam.
The area around either spillway may continue to erode away. The main dam structure is currently not in danger. They don't want to run the main spillway at all but they also don't think they can rely on the emergency spillway.
It would still be a catastrophe, the outflow will go from inches per hour to feet per hour.
Okay, this makes more sense. The problem is that the spillways will fail in the sense that the downstream capacity cannot handle the volume of flow, so will flood those regions, as well as possibly flood areas not typically even near water as it carves its own paths.
You have to remember that the hill _is_ the dam (of the type[1]). so when water flows down that spillway, it's going to pick up dirt with it - making the hill smaller and smaller, ie. making the dam thinner and thinner.
But if it eats up the spillway upwards it engangers the little part of tho damm where the vales are. If you do not have a concrete lip like on the auxillary spillway and it just flushes over the top of the hill it will quickly carve a lot deeper, so you have more water than just what was held back by the smaller wall.
Also: the top 70 meters or something is still a lot of water!
You're drawing distinction between the 'man made' part of the dam and the 'natural' dam, which exists on paper but not in the static force analysis. If that natural portion of the dam becomes unable to support the weight of the water, there will be a collapse.
Glen Canyon was slightly different because there was no "emergency spillway" in the same way that Oroville has. Glen Canyon simply had 2 giant spillways that both needed to be in use but were both getting torn apart by cavitation. They ended up adding plywood along the top of the spillway gates to give themselves a little more reservoir capacity to wait out the flooding upstream but honestly they just got lucky. The only option they had at Glen Canyon if they exceeded the plywood barrier would have been to let water flow down the main spillways and possibly damage the dam.
The erosion on the primary spillway is looking pretty nasty. Even if / after they manage to keep the emergency spillway from collapsing, they will probably need to continue running the primary spillway at a high flow rate to get the reservoir down to safe levels to ready for future storm systems and the coming snow melt, and this will continue to eat away at the hillside (they're currently dropping lake levels by 4" (!!) an hour). That's a significant outflow. It's a good thing that the spillways are decently far away from the actual dam structure. But it sure is going to be one expensive cleanup operation in the dry season..
Fingers crossed that things stay drier and cooler for the sake of all these people
First, and importantly, my hopes go out to everyone that they are able to evacuate safely, and that nothing bad happens.
I wonder, how do you test for something like this? I mean, you can certainly plan, and I imagine that the emergency spillway was examined at the time it was planned, but no plan survives contact with the enemy, and the best thing to do is to test.
But, to test the emergency spillway you need to fill the dam to the point where it's overflowing, and I believe it's been a few years since we've gotten close to that. Certainly not any time in the last year.
Besides, if it was tested in the past, it may be that the drought conditions--followed by all the rain--changed the soil in such a way as to enable this.
I need to make a note to read the report when it comes out; I'm sure it'll be interesting.
> “Anytime you take on a situation like this where you seek to evacuate thousands of people on very short notice, it can be a chaotic situation,” Honea said. “We understand that.”
> Sunday night gridlock as Marysville residents evacuate
> After having to evacuate several times before, Agrifoglio said, she was used it.
> She’s confident her husband will be able to evacuate if he needs to, but Tommy would have to wait out a flood.
> Erin English of Linda said she got a robo-call a few minutes ago telling her to evacuate and get to higher ground.
Thankfully, it appears the actual body of the dam is unlikely to fail, so hopefully even if the emergency spillway fails, it won't be a catastrophic, immediate draining of the whole lake.
It's not a question of patching cement; you have to reconstruct the slope that's been worn away under the spillway. We're talking about huge amounts of Earth.
Couldn't you just bring in a few oil / gas pipes (or whatever you happen to have) and siphon it in a more controlled manner? The country doesn't seem to have a problem in creating oil and gas piping networks quickly...
40 million cubic meters in 24 hours means just 15 2m diameter pipes running at 10 m/s.
I would imagine the same amount of water flowing over a longer period time would cause less erosion even if the pipes wouldn't reach all the way down...
Edit:
You could even do it with 6000 20 cm diameter pipes, probably plastic would do.
Gravityloss says> "Couldn't you just bring in a few oil / gas pipes (or whatever you happen to have) and siphon it in a more controlled manner? The country doesn't seem to have a problem in creating oil and gas piping networks quickly..."
Good idea, but this is happening in CA, where pipelines don't sprout so quickly.
I think the issue is the speed with which you'd have to implement a solution. It does seem easy, but maybe not to coordinate that construction to happen in less than 12 hours.
Is hydro more dangerous than nuclear? The Banqiao and Shimantan Dams killed 171k people, whereas Chernobyl killed 30 people directly plus an increase in cancer risk. No one died directly at Fukushima, though zero to hundreds could from radiation exposure depending on the estimates. About 18k died in the tsunami.
(I just realized the Oroville Dam is for a reservoir rather than power generation, but the risks are similar.)
Snowmelt. If you look even further back[1] you'll see that it's cyclical. Peak runoff these days is usually March-April[2], so by May reservoirs should be maxed out. The past few years have seen a major drought, so the curve can be pretty dramatic.
The main spillway has been running at 100000 cubic feet per second. To carry that in 3 foot pipes (7 square foot cross section), you'd need hundreds or thousands of them (so a few just wouldn't do much of anything).
Same with trying to bypass the water to somewhere else. To make a difference the bypass needs to be at a similar scale to the spillway, carrying tens of thousands of cubic feet per second.
The worlds largest pump, located in New Orleans, cost $500 million, cannot move enough to match the spillway. You would need 5 of those to match the flow. But realistically, a pump that can move 10.000 feet^3/s would greatly reduce the stress on the rest of the pathways. Problem is, we cannot just rig up a temporary pump with that capacity.
See https://what-if.xkcd.com/147/. Niagra Falls is usually flowing at 100,000 ft^3/sec, the same as the spilway. Granted your 3ft pipe is a bit bigger than a drinking straw, but closer to the straw's scale than the spillway's!
However, watching the tweets trying to make this political has been sickening. The number of people wishing to "send liberals to Oroville" is nothing short of mind boggling. What. The. Actual. F?!?
I heard about this damage a few days ago and thought it was interesting, but now I find out there's this huge conspiracy scene around it. Stuff like 'the gov't is in CYA mode and trying to downplay risk' to 'this is a false-flag attack to undermine Trump'.
It's just so weird that this seems to have people frothing at the mouth. How did so many collectively decide to adopt this narrative?
If the bots and sockpuppet accounts on twitter are any indication of sockpuppetry among public internet forums than it's safe to assume there's a significant and non-trivial amount of postings coming from agenda pushing organizations.
The "false flag" stuff is just loony. But there is an element of CYA because previous rounds of funding allocation have apparently evaporated into the ether.
No, maintenance to existing infrastructure. This distinction is important. Most people think of new roads, bridges, dams, railroads when they think infrastructure. Politicians love to attach their names to such things so they get funded first. Often at the expense of keeping existing infrastructure.
You see this all over, roads that people use in bad shape while new "roads to nowhere" are being built.
TIL the Oroville dam is the highest in the USA, 44 feet higher than the Hoover dam. It's kinda mind boggling that it could actually fail tonight (though the latest reports indicate that the situation is improving).
to clarify: it's not the dam itself that's at risk of failure, but the emergency spillway. while this scenario would be catastrophic, it's far less catastrophic than the entire dam failing
Think about that statement, what does is mean to you that the "emergency spillway failed" ? The ES is the portion of the dam that is slightly lower than the overall height of the dam so that in the event the main spillway was unable to release water fast enough, the water would start spilling here rather than across the dam. If it "fails" then a portion of the dam ceases to exist. That releases water through that hole uncontrollably. At which point losing containment is generally a matter of when not if.
If it fails, it will be a double disaster, many people will lose property, and California will lose some or all of the water in its largest reservoir. The challenge is going to be keeping ahead of it through to the next storm.
The emergency spillway is around 30 feet high, the dam itself is 770 feet high. The amount of water released from a failure of the emergency spillway will be enormous, but still much smaller than the amount of water released by a complete dam failure.
Excellent link, thanks. I found the following comment sobering:
"Countryman: It’s not going to be the (main) embankment failure, but it’s a failure. If it does happen, there’s nothing saying that the ground is going to stay where it is. That force of water will start tearing that hill apart, and it could eat back into the reservoir and drain the reservoir."
> At which point losing containment is generally a matter of when not if.
No, it's not. The local geology is fairly solid rock. The overflowing water will wear down the overlying soil and loose Earth, but should be sustained by the rock formation. It is a risk, certainly, but such a site is chosen because of the suitable foundation.
The issue right now is to see how the spillway fares over the night. If it handles the increased flow, then it should be able to continue to relieve the situation.
To be fair, I think it is a little ethically troubling to refer to the emergency spillway as anything other than that (e.g. auxiliary spillway), but it is designed to function in an emergency, not just fail catastrophically.
I'd love to get a source on this info. I've been looking for info on the geology of the exact area and the dam construction to assess this exact point.
Where did you find the info on the area being solid rock?
That would go a long way to giving an idea as to how bad any increased failure might be.
So far, the only failure foreseen is to the auxiliary spillway which would definitely lead to an uncontrolled release of water from the lake, but is a separate structure from the main dam.
There's definitely worries about the erosion on the main spillway moving back upstream towards the dam, but that is something folks are going to have to look at and consider over the remaining duration of the water season, unlikely to be a danger tonight.
No, the emergency spillway is part of the dam. Failure of the spillway could lead to failure of the entire dam. It's not likely, but it's possible. Once large quantities of water start going where they weren't designed to go, all bets are off.
You should look at the dam from maps or satellite. The spillway is off to the side, away from the dam (clearly, by design), and the emergency spillway is on the far side of the main spillway from the dam, so while the spillway failing would be terrible it should not damage the dam itself.
Looks like you're right. I read somewhere that the spillway was part of the dam structure, but now I can't find that reference any more, so I guess I must have misread it.
"It’s not going to be the (main) embankment failure, but it’s a failure. If it does happen, there’s nothing saying that the ground is going to stay where it is. That force of water will start tearing that hill apart, and it could eat back into the reservoir and drain the reservoir.
The hillside underneath the overflow spillway is literally washing away. You can see downhill portions of the spillway where the waters ate away 10, 20 feet of vertical elevation. If that erosion backs all the way up to the reservoir itself, then the lining could fail (much as the main spillway did). At that point, it doesn't matter if the dam is still standing, if there is a gash right next to it lowering the effective maximum water level by several feet.
I don't know enough about the geology of the area to know how likely it is to happen. But history does show that dams can go very quickly once erosion reaches the dam/reservoir, so alarm isn't exactly unwarranted.
Why is this being down voted? The geology of the area is such that the emergency spill off can't be eroded down to the valley floor. That's why the location was selected.
I imagine the most straightforward way to patch a hole, at least for a short period, is to use the water pressure to your advantage and inject objects to plug the hole from the dam side. Perhaps a thick metal plate lowered onto the main breach, and then malleable plastics/rubbers to slow seepage around the plate. Could probably push a hotfix out to master in a few days, for far less than 100 million dollars.
Disclaimer: I haven't found any details on the design of the emergency spillway and the suspected damage, so this is speculation.
The main dam has no holes, so there's nothing really to plug. This is not what's going on in this case. The erosion of the spillway isn't a failure of the main dam, it's just a badly damaged portion halfway down the hillside where they would be sending the overflow water. this means that the overflow water is causing even more erosion as it eats away at everything it's flowing around.
Are you fixing it or are you making the inevitable failure even more dangerous? The answer is not easily determined.
The current solution is to drain the reservoir of water as fast as possible--this removes pressure on the hillside, and reduces the scope for damage should the thing actually go.
As for actually patching it, the solution is dumping lots of grout. But that only helps if the slope is actually stable and capable of supporting the embankment and dam. If the slope is washing away, all of your patching is just adding more weight to a structure that can't support its own weight anymore.
Now this guy was a great salesman. It leads you to wonder if his apparently high success ratio was a result of pure luck, if there's some truth to his "evaporative mix," or as suggested in the article, he had great meteorological prediction skills.
If weather patterns are not independent one year to the next, then just the fact that only statistically significant drought-ridden cities call for his help probably suggests that all of these cities are "due" for rain regardless.
