Oroville Dam Emergency Spillway Expected to Fail within the Hour

February 12th, 2017 by Roy W. Spencer, Ph. D.

So, it turns out all of that bedrock that made the Oroville Dam design so fail-safe is not going to stand in the way of Mother Nature.

Mandatory evacuations have been ordered, and the emergency spillway is expected to fail within the hour.

Flash flood warnings have been issued. This will affect Oroville all the way to Sacramento I assume.

UPDATE: Evening briefing announcement that a hole has developed slightly downhill of the base of the 1,700 ft-long concrete portion of the emergency spillway. Here’s a screenshot from this evening from the KCRA-TV helicopter with my annotation of my *guess* of where the problem might be (they were NOT specific in the press conference). They said if the hole migrates uphill much farther and undercuts the spillway, the concrete portion could fail, which is why the evacuations were announced. (Another view I’m hearing is the problem is at the left end of the spillway, not at the right end.)

Frame grab from KCRA-TV helicopter video showing water over flowing the emergency spillway at Oroville Dam, evening of Feb. 12, 2017.

The flow out the main spillway has been increased to 100,000 CFS, which should stop the flow over the emergency spillway tonight. But even if the concrete does not fail tonight, I suspect the problem won’t go away as new rain systems are forecast in the coming week, and snow melt season hasn’t even started yet.


Updates at: https://twitter.com/Oroville_Dam

Live helicopter video from KCRA-TV

66 Responses to “Oroville Dam Emergency Spillway Expected to Fail within the Hour”

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  1. Resourceguy says:

    Was rebar left off of that structure also?

  2. I’m guessing that the flow has undercut the concrete spillway, weakening it. Why hasn’t this possibility been made public? I have seen all kinds of opinions that since the spillway is on “bedrock”, it shouldn’t fail. But maybe it’s sitting on fill of some sort?? I suspect we will find out engineers had concerns that were not allowed to come out. Gonna get interesting.

    • Eric Barnes says:

      It seems like the concrete weir is sinking into the ground. Comparing videos of the Emergency Spillway with those this evening makes it seem like the top of the weir has dropped at least a few inches as it seems like more water is going over the weir even after the lake level started dropping. Must be fill under the concrete structure IMO.

    • dp says:

      If you use Google Earth to explore the dam area you will see where the emergency spillway joins a simple impervious barrier wall held up by soil. This is very close to the parking lot. Water is currently issuing at the interface between the emergency spillway and that barrier. And that is where the erosion was happening. Had they not been able to draw down the lake level below that barrier it would have eroded the cobble on the slope side of the barrier and it would surely have failed. Remains to be seen if it survives the next storm and the main melt headed their way.

    • barry says:

      I suspect we will find out engineers had concerns that were not allowed to come out. Gonna get interesting.

      Engineers have been saying they don’t know why the spillway fractured.

    • Beyond Concerned says:

      It is sitting on the hillside which is up to 60′ of dirt on top of bedrock.

      • Lester says:

        Right, the bedrock is not El Capitan smooth at the correct slope. If you do notice where the soil (fill) has been eroded away and the bedrock is not exposed it is holding up pretty well. People that hang out in Yosemite with a bit of geological curiousity are not shocked. CA bedrock is pretty dang tough.

        I would guess it would cost more than the entire dam to reinforce and lock the spillway into the bedrock for its entire course.

        The question I have is how much fill is under that emergency spillway at the crest?

  3. KB says:

    Pretty myopic analysis prior. Defacto two earthen spillways around an earthen dam running at max capacity? When the primary spillway began to fail that was the death bell ringing. Trees meet forest.

  4. Taco joe says:

    If you have a soul, say a prayer.

  5. Eric Barnes says:

    Is the weir being undercut? It seems like the flow over the top is much larger than it was earlier this AM?

  6. Mark Ping says:

    The concern is the weir being undercut from a hole on the side (reports haven’t been fully clear).

    They say there’s a “hole” on one side of the aux spillway, and the sheriff is saying they’re going to be dropping rocks, etc. to shore up the whole.

    As of just a few minutes ago, the level has lowered to 4 inches over the spillway. It’s going down by 2-3 inches per hour.

    I live in Chico, and we’re setting up evac centers, sending groceries and water to those centers etc.

    Even if we get through tonight safely, there’s another sizeable weather system coming in this week and even at max spillway, it’s unclear what’s going to happen. We have a lot of friends in danger, and everywhere from Oroville to Yuba City (about 100+ miles) are being evacuated.

  7. Password protected says:

    Nature always wins in the long game.

  8. Mike Flynn says:

    Dr No wrote –

    “It is amazing to read the analyses of the Oroville event from the armchair experts here.
    They seem to have panicked unnecessarily in the face of the advice from the real experts who maintained there was no risk of a dam collapse nor of any serious flooding downstream.

    Their comments reflect the level of informed debate that surrounds climate change.”

    Oh goody!

    Good to know that the climate change level of informed debate is keeping everyone safe.

    Predictions are difficult, particularly when the future is involved.

    My sympathies to the people whose lives are being disrupted.


    • dr.no'satroll says:

      Alright No, where ya hiding? (i wanna slap your stupid a** around a while)…

    • Gordon Robertson says:

      dr no…”They seem to have panicked unnecessarily in the face of the advice from the real experts who maintained there was no risk of a dam collapse nor of any serious flooding downstream.

      Their comments reflect the level of informed debate that surrounds climate change.”

      Is that why they are evacuating people downriver? You alarmists want to proceed with drastic change regarding climate when there is no evidence for it yet when a dam is on the verge of collapse you rag on people who are concerned about it.

  9. RiggingRich says:

    As a technical artist with a technical creative mind, I have some questions. First they knew that with this years current weather pattern they might fill up the lake, why didn’t they inspect it so preventive maintenance could have prevented erosion? IE dump large aggregate at the base of the emergency spillway, or check the main spillway. They must have seen 3 weeks out that they were on track to fill up. Also why did they design a emergency spill way that might fail after 2 to 3 days of use? Was it not maintained? Why would you tell the world that its built on bedrock and then secretly build it on fill? Or maybe build a ramp for the emergency spill to run down so that erosion wouldn’t be a issue?

    Second can they not fly up large boulders to fill the holes to prevent further erosion? I know there are some really big logistics to this statement as I don’t know what the load limits are, finding one of those dredge grabbers and hooking it up to a helicopter so that it works, trucking in said boulders with a cat to load the grabbers, etc. Maybe my artist brain is being to creative. I know that would require the government to do something and they might not be people of action. Why aren’t there any emergency plans to address this issue other than run for your lives?

  10. Darwin Wyatt says:

    Maybe a whistleblower will come forward and explain how this happened…

  11. BBould says:

    When I found out about the huge break and hole in the spillway is when I started to not fully trust the engineers rosy outcome. When I heard the emergency spillway was in use I was very worried for the people in town, bedrock or no bedrock, water flow of this magnitude is very destructive. I sure hope this dam holds.

  12. KevinK says:

    Well let’s all hope for minimal loss of life/limb/property.

    There will be lots of “Second Guessing” and “Monday Morning Quarterback” moments later.

    Everyone effected please be cautious and safe, I wish you the best of luck and I hope the “predictions” turn out to be much worse than the actual outcome.

    Best of luck to all involved.


  13. Mark Ping says:

    The latest news is that water is no longer coming over emergency spillway. That’s great because the evac order (more like 60 miles, not 100 as I said above) was due to the danger to the emergency spillway failing completely.

    They’re now intending to keep drawing down the lake level so their’s plenty of buffer for the next storm.

    Keep in mind we’ve been in historic drought for the last 10 years, and Lake Oroville is where a lot of our fresh water comes from. Had they released much more water than they did in preparation for the storm, there would have been quite the uproar in the state, because “why are you wasting all that water?” As it is, hopefully this will finally get the additional water storage projects underway for the state.

    Gov. Jerry Brown has been too busy playing with his fake train project to deal with the water situation.

  14. RAH says:

    I noticed that in the briefings where they kept uttering reassurances again and again they started calling what they had previously referred to as the “emergency spillway” the “auxiliary spillway”. Instead of being reassuring to me that was a warning sign that there was bad news they knew or suspected that they weren’t telling the people.

    In addition they kept saying the “auxiliary spillway” was flowing way under design capacity while at the same time telling the people that they were continuing to use the primary spillway. That didn’t make sense to me at all.

  15. Rick B says:

    To all Californians. Wake up. Gov. Moon beam is directly responsible for the out come of Oroville dam mis- management. For years now he has directed funds to be spent(while raising taxes) on water tunnels,and trains to nowhere. He now want’s to raise the gas tax 30-40 cents per gallon to be pissed away with funds that are suppose to be spent on roads, bridges and water storage. No wonder Northern California wants to be a seperate state. As long as he is in office you can forget about any real issues being solved. I hope a few ‘heads roll’ for this blatant disregard for safety.

  16. Tim S says:

    The distance from Oroville to Sacramento is about 70 miles direct, and the difference in elevation is about 170 feet (194-26).

  17. ren says:

    LIVE Webcam at Lake Oroville California
    Emergency spillway has become severely eroded
    Traffic in the area is gridlocked due to evacuation of 130,000 people
    The 770ft dam is the nations tallest
    The dam went into operation in 1968 and has never had a problem
    Authorities hope to use helicopters to drop rocks into the spillway to plug it.

  18. Tricia says:

    The same words came out of my mouth in the first 5 minutes after I found out from a friend what was happening!

  19. ren says:

    The solar wind very weak. Jetstream descends far to the south and threaten California.

  20. RAH says:

    Too funny. California, the state that has led the way in bombastic statements and violence in their opposition to President Trump and his administrations policies are now begging for help from that very same “Nazi”. http://www.breitbart.com/california/2017/02/12/california-governor-asks-president-trump-help/

    Don’t want to see no more BS articles about California succession or defiance of Federal law after this!

  21. Lewis says:

    Dropping rocks into the stream will not work except under certain restraints. There would have to be enough of them to actually divert the flow. The problem is divert the flow to where?

    The water will go around the rocks, actually washing away the dirt faster because it now has to go around the rocks. The same amount of water will be flowing from the top, the rocks won’t stop that at all.

    The best option the emergency spillway, which while injured is not destroyed. As long as it is not cutting up the hill at any great rate, it should work fine.

    Even then, if the top is actually set in rock, which it seems to be, at some point the up cutting will slow or cease and the system will stabilize.

    The problem seems to be only the emergency spillway.

    So far as Preventive Maintenance – someone alluded to the cause of the problem in the prior blog – the loss of soil under the spillway which wasn’t visible until the collapse.

    That could have been check for, but wasn’t for various reasons. Perhaps it will be in the future.

    And most importantly, dams are useful for many things. Flood control is only one. But flood control only works most of the time. At full pond there is no control any more.

    We’ve seen that in North Carolina on the Catawba River many times where heavy rains fill the various man made lakes along the river until they are full, then the only thing the operator can do is let the water run. Then, low and behold, the people downstream whine that the water is rising.

    My point: It is difficult, if not impossible to plan for the occasional unusual weather event. But they will occur, it is just a matter of when.

    The moral of the story: Don’t build in flood plains. They will always be flood plains.

  22. ren says:

    The worst case scenario

    There is no map showing exactly what will happen if the emergency spillway collapses tonight. Officials only have a map showing a failure of the dam. That worst case scenario is useful in that it shows where water goes and how fast it gets there.

    Water would get to the town of Oroville within an hour.

    If Oroville Dam were to suffer a massive breach, water would get to the town of Oroville within an hour, according to GIS maps maintained by CalFire.

    Within two hours, the small town of Briggs would be affected. In three hours, Gridley would be hit. Water would reach Live Oak in five hours..

    It would take eight to 12 hours for the water to get to Marysville and Yuba City.

    If the dam completely failed, flood depths could reach more than 100 feet in Oroville and up to 10 feet in Yuba City.

    The CalFire maps represent a catastrophic breach and are not necessarily indicative of what could happen tonight.

    • ren says:

      “Its uncontrolled

      5:30 p.m.

      Fearing a gush from Lake Oroville if the emergency spillway collapses, officials are releasing as much as 100,000 cubic feet per second from the main, heavily damaged spillway in a frantic effort to drain the lake below where it spills out the emergency structure when the lake reaches maximum capacity, said Kevin Dossey, an engineer and Department of Water Resources spokesman.

      The levee-line downstream channels in the Feather River could hold more than 150,000 cubic feet per second, said Maury Roos, a DWR hydrologist, but he said theres a possibility that a levee could breach from the pressure.

      Roos said that below where the Feather River merges with the Yuba River, levees are rated for a capacity of around 300,000 cfs.

      When asked how much water could be released should the spillway collapse, DWR spokesman Chris Orrock said, Its uncontrolled. Its uncontrolled.

      Dossey said the emergency spillway was rated to handle 250,000 cubic feet per second, but it began to show weakness Sunday at a small fraction of that. Flows through the spillway peaked at 12,600 cfs at 1 a.m. Sunday and were down to 8,000 cfs by midday.”

  23. Eric says:

    The incompetence of the people running California is astounding. The PR people are failing in grand fashion.

    First off, anyone could tell days ago that this was a serious problem. At that point they should have told people to get ready for an evacuation. Pack valuables, secure house, fill gas tanks and get cash just in case.

    If and when this fails later this week the headline should read “When Politicians Kill”.

  24. spalding craft says:

    Failure of the concrete spillway wouldn’t increase the volume of the water coming over the dam, right? Only thing that would do that would be a failure somewhere that lowers the level of the land around the dam, thus releasing a huge quantity of water.

    Is there any danger of that happening?

    • Curious George says:

      No water is coming over the dam. Spillways are separate structures on another hillside.

    • Bob Cherba says:

      Unfortunately, the whole discussion of possible failure of the emergency spillway at Oroville Dam involves the blind leading the blind . . . and I’m about to add my comments based opon questionable reports.

      The concern as I understand reports is that there’s a spot at the base of the emergency spillway which is being eroded, and there’s concern the erosion could/may/might undercut the spillway leading to a failure/breach. This would increase the volume of water being released and could/might be substantial.

      While it’s an earthen dam, the emergency spillway was built on bedrock. Can the spillway concrete/bedrock interface survive the erosion? Nobody knows.

      Commenters have been sloppy about referring to the spillways. The normal spillways pass through the turbine-generators. At one time they were not in use because of the large amount of debris. The auxillary spillway has been in use and is the one with the large hole that Dr. Spencer featured a couple of days ago. The emergency spillway is a passive “device.” When the water level reaches the top of the spillway, it overtops it. It doesn’t require any human action. The water doesn’t break the spillway, so I don’t think it’s correct to say the water “breached” the emergency spillway.

      • Bob Cherba says:

        Screwed up again.

        The main spillways don’t go through the turbine-generators, but are part of the main dam structure. It was reported that they were not in use due to the large amount of debris.

        I haven’t seen any reports on whether the turbine-generators were/are in operation.

  25. Beyond Concerned says:

    The hole that they are concerned about is all the way on left hand side of the above picture. There is a video from a chp plane taken last night that shows the hole with brown water (indicating erosion) pouring out of it while the other streams are relatively clear.

  26. Beyond Concerned says:

    They have a goal of lowering the dam by 50′. Unfortunately that will take 6 days and it is going to start raining on Wednesday. Additionally they are causing a ton of erosion on the main spillway by maintaining flows of 100,000 cubic feet per second. So they can’t use the emergency spillway and they main spillway is cutting into the hillside that holds the dam up. Not good. The upcoming rain will push this dam to the brink.

    • Beyond Concerned says:

      The upcoming rain could easily push the inflow from 40,000 to 150,000-200,000 cfs. This would refill the lake in 1-2 days. Hopefully whatever they do in the next day or two will be enough to stop the erosion on the emergency spillway. It is a very steep slope and they are dropping rock onto 40′ of loose soil. So not good and it is not likely that they can prevent erosion of the hillside if the lake fills again. At that point the emergency spillway would collapse and that would cause the main spillway gates to collapse and then the attachment of the dam to the hillside would be compromised causing the pile of clay and river rock that they call a dam to fail. It is worth noting that all of this information can be gleaned from the department of water resources previous press conferences in the last week. Of course it appears that they have now removed those press conferences from their facebook account.

  27. ren says:

    Need to be removed much more water from the reservoir in a short time.

  28. Curious George says:

    Situation is under control. Governor Jerry Brown is now personally directing the work. His knowledge of all accounting tricks will undoubtedly solve any remaining problems.

  29. spalding craft says:

    It’s still my understanding that the dam itself is fine. The concrete and emergency spillways are under huge pressure, though. But even if there were a failure to the spillways that would not increase the volume of water being released from the lake. And I haven’t read anything that indicated erosion near the dam that would compromise the dam itself.

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