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  1. KenMH

    KenMH Member

    No, and this point is one I have been a bit worried about. it's a can of worms though if we go down the road that some of the basic foundation preparations were inadequate, every little shadow of every little rock is going to be evidence of something. Its a hard road, but we may need to travel down it. I dont see any dental grouting or surface sealing or crack and gap grout injection, at all, anywhere in the bedrock cut that all the manuals and safety and design videos call for.
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  2. CRM114

    CRM114 Member

    250K is only the main primary (concrete) spillway. The emergency handles much more:

    Oroville Dam Spillway Failure

    The combined capacity is well over 500K, I believe, and there is a lot of storage to burn up before you get to max elevation. I moved my post here:


    From that, peak inflow is actually 725K CFS for their current Probable Maximum Flood, but it looks to me that that would occur before you've topped out the water level (depends on where water level starts at). So peak inflow occurs before peak water level and that inflow dissipates in storage, reducing your required outflow.

    There is no problem with flow capacity, except that the PMF appears to have grown since original design - it's the erosion.
  3. Mick West

    Mick West Administrator Staff Member

    Good find, and there seem to be several other Oroville documents:




  4. AlmostaCE

    AlmostaCE New Member

    An excellent question I think. Overall, I don't see any way to replace/update the drain system in the upper section without removing the interior panels of the spillway. One could reasonably retain the 2 sidewalls and excavate outside of them to replace the longitudinal drain piping, but the laterals or diagonals would require removal of the existing floor slabs.

    To your point, I don't know that it would be necessary to go all the way to the gate house - the photo evidence we've seen seems to indicate that the drains do not become flowing until some distance down the spillway. However, it may be determined that floor panel modifications need to be made closer to the gate house in order to satisfy other design criteria.
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  5. Junkie

    Junkie New Member

    I don't see any drains near the top that aren't flowing. They don't start until some distance down the hill because they need to collect water from under the slab and then flow downhill to an outlet.

    Or am I missing some drains near the top that aren't flowing?
  6. Scott Gates

    Scott Gates Active Member

    Simply look at the natural channels cut by the emergency spillway outflow. No significant channel erosion despite the concentrated flow. And clear blue-green bedrock shown for the length of the channel from the bottom of the bench below the weir to the river.

    Add that we know the builder went to significant extra expense and effort to insure the weir is built on solid bedrock.
  7. edi malinaric

    edi malinaric New Member

    Last edited: Feb 18, 2017
  8. KenMH

    KenMH Member

    How hard is it to replace the entire spillway with modern methods? I feel there is a disconnect in our society about the massive positive economic impact of the dam and the costs involved. It feels like a friend telling me they will get around to having an oil change some day when we are driving to work and their car is making awful noises. The transportation costs are part of the income plan!!!! Want peaches cheap? Better fix the dam. best memory department is driving through the orchards below this dam in spring and smelling several thousand acres of one crop ripening, in the case of the peach tree orchards it's unbelievable, like driving through a ripe peach. Gives a human a feel for what its like for animals that use their sense of smell primarily. It's sort of an amazing experience. Hope this isn't a rant but more a relation of what the dam's impact is including a personal account of the wonders of the growth cycle allowed by the irrigation the dam provides. If it's a rant delete away I understand.
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  9. AlmostaCE

    AlmostaCE New Member

    I believe you are correct - based on this photo from post 995 it appears that there are just 3 sets of drains between the gate house and the point the flood control channel becomes convex.

  10. Mick West

    Mick West Administrator Staff Member

    It's time and money. Several years and over a billion dollars. Using the Folsom auxiliary spillway as an example. That cost was justified by the danger to the city of Sacramento.
  11. AlmostaCE

    AlmostaCE New Member

    I encourage folks to review this study regarding the flood control and spillway designs - its interesting to note how much the final constructed unit differs from the initial proposed designs, including some designs that initially included a larger outlet works for both normal and flood flow rates.
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  12. Scott Gates

    Scott Gates Active Member

    There are already numerous modelling programs that can calculate different effects. I am certain simulations have been run on numerous failure modes and they know the effects of each.

    The emergency weir is engineered to withstand the full force of the lake. Builders went to considerable effort and expense to insure solid bedrock as a foundation. The ogee weir is as much as 64' wide at its base and weighs somewhere in the range of 80,000 to 130,000 tons (guesstimate). The design took into account things like this and overturning etc.

    The base of the weir is also significantly below grade on the reservoir side - with as little as 6 to 10' exposed at thge parking lot end.

    Knowing what we do know it is highly unlikely the weir is moving anywhere. It is also unlikely backcutting from the bench below it could ever cut thru the weir or its bedrock foundation. The engineering required was well understood even back then.

    It is far more likely a failure could occur at the parking lot end of the spillway. There the "wall" is small, and only several feet below grade. If backcutting reached the wall there it could easily cut under it by all appearances. That said it is more than 500 feet to deeper water (and with bedrock near the surface) and any v notch that would form would not likely have sufficient flow it would seem to grow very far ...
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  13. PhyllisO

    PhyllisO New Member

    Seems that Shasta folks are none too happy about losing any dams. Wonder if the Oroville events will strengthen objections to dam removals. Also, note quote from 45's Interior guy, to the effect that "we throw them up, not take them down."

    Last edited by a moderator: Feb 18, 2017
  14. alec

    alec Member

    Based on the earlier posted cross section of the ogee weir(post #745), there is a 4' 0" facing of enriched concrete. Given that, it's shape and it's mass , it's recent short testing ,the concrete likely can handle large smooth flows well. The major unknown is what effect a river running down that hillside will have. The first minimum effect will be substantial debris deposition in the channel. Likely , there will be some surprises in channel formation due to non - homogeneous hillside conditions . With what we've seen so far , a broad categorization of the hillside materials might be soil, frangible bedrock, and coherent bedrock . A diamond is extremely hard, yet cleaves nicely along cleavage planes. Weakpoints matter.
    The major unknown and unknowable is the weather within the drainage basin, and if one cares to consider the effect on saturated full drainages down stream, that could also be taken into account. The Lake Oroville watershed is what determines flows Oroville dam and its peripheries (arguably an artificial distinction, as they are necessary components of a functioning dam system) must contain. Current Lake Oroville elevation is 854 +, an optimistic projection was to have reached 850' by Wednesday (midnight Wednesday 872'+) I don't know what the projections for the current influx for the lake elevation are. I do hope they are closer to actual results and especially hope they are not overly optimistic. The concrete spillway is far more degraded than it was two weeks ago.
    I mention these points, not to cast blame, nor be alarmist, but to focus attention and clarity of thought on where things are truly at right now and what forces are determining lake elevation. Currently all releases are through the concrete spillway, please correct if the penstock (14,000cfs max) is now operational. Current concrete spillway release is 65,000cfs. I understand there has been additional new erosion on the west bank of the spillway discharge , but have not seen imagery from today which clearly illustrates the extent of this. At minimum , there's additional debris in the river channel adding to the workload of clearing that channel.
    I believe some amount of water is currently held as snow in the drainage basin ( an earlier quote described this as 31", I read that to be the water content equivalent of 31" of rain, which seems high as the moisture content of snow, even were it to exist across the entire basin should be lower than rain which is 100% moisture content as judged by rain gauges, please explain) Still some amount is upstream and has not melted. 1862 warm weather did suddenly melt snow early in the season, so there is known historic precedent for this phenomena.
    This year has been strange, long, and wet (150-180% of "normal" snowpack are the published numbers I read in the Los Angeles Times when they describe ongoing Sierra snow surveys). Northern California is well saturated, dams are full, river flows are high and the current NOAA forecasts for Chico posit rains, heavy at times into Tuesday with snow elevations at 6,000-6,5000. another unusual feature of some storms this year has been rain at high elevations (9,000'+ at Mammoth, in January!) I have not seen longer range forecasts for March, but am certain days will be longer, and it's likely to be still warmer overall than February . Under "normal" conditions, and with a slow even, gradual spring melt it would be a challenge to manage the spring flows. A potential complication this year is that, warm, wet storms, can transform a slow even melt into a more episodic pulse driven event. The high water capacity of the current snowload can quickly mobilize as an addition to a warm storm's rain quantity. The drainages don't distinguish between melt and rain . Water is water, flow is flow . If such were to be the case it seems , that as large a reservoir capacity as possible might provide a buffer to pulses.
    This seems especially important in light of the amount of damage we've seen in the primary regulatory system of Lake Oroville. Acknowledging the real possibility of such pulses, without debating the odds of occurrence , it seems this is a more than a low risk, with very high consequence environment we are in. Weather dependent. Current downstream flow regulation is based on the concrete spillway. If that control were to be put on hold or sidelined, it does seem to be what's left is the penstock (14,000cfs - inadequate) and the emergency spillway (no flow control)....i.e. were the reservoir to fill all (or all -14,000cfs in the best case) flow into Lake Oroville would merely exit over the emergency spillway at about the rate the inflows come in with no flow regulation and no buffer for high pulses.
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  15. PhyllisO

    PhyllisO New Member

    This Jan. 29 story from the Siskiyou Daily News shows that the new Interior at least likes more dams, not fewer.

    Yreka meeting attendees say no to dam removal
    By Danielle Jester
    "More than 100 people attended the last in a series of three meetings Thursday in Yreka seeking public comment on the planned removal of four dams along the Klamath River, and the overwhelming feeling expressed by Siskiyou County residents was outrage....
    "Public officials who spoke during the meeting included Siskiyou County Board of Supervisors members, County Assessor Mike Mallory; and Erin Ryan, a staff member for state Rep. Doug LaMalfa, R-Richvale.
    "All essentially spoke in favor of leaving the dams in place, with Ryan stating that LaMalfa had sent her with a message for Siskiyou County citizens: 'Zinke told me, "'We don't pull down dams, we put 'em up,'" in reference to President Trump's Interior Secretary pick, Rep. Ryan Zinke, R-Montana. The remark was met with cheers from the crowd."
  16. Shadowwalker

    Shadowwalker New Member

  17. Tom1

    Tom1 Closed Account

  18. Brad P

    Brad P New Member

    Why would you replace the entire Main Spillway? The top part didn't fail and appears to be holding up well under large flows. Part of the bottom failed and the erosion appears to have stopped after significant flows. By washing away the overburden on the bottom part, the bed rock is now exposed and seems to be working quite well at dispersing the energy of the flow. They probably need to modify the area where the water leaves the spillway, but I don't know that they need to put it back the way it was.

    Of course we can't see what the remaining portion of the Main Spillway looks like until they turn off the water, but if it is sound, and testing shows that the drains are working and it's holding tight, I don't see that it all needs to be replaced or even rebuilt. Those decisions need to be made after the water has been turned off.
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  19. whoosh

    whoosh Member

    In case you haven't seen it, the NWS model output for 5 days is well formatted for civilian consumption.

    Follow this link to get started.

    The DWR and maybe other authorities certainly have some means by which they can manage both flood control and water delivery from and to complex networks. Pretty impressive operation.
  20. bsd43

    bsd43 New Member

    Does this help? Link to: State Plan of Flood Control Descriptive Document
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  21. Scott Gates

    Scott Gates Active Member

    Bedrock (or at least bottom of base of weir) - from my interpolation images above - is appx 836 at the main spillway end. It ramps upward from what we can tell to the parking lot which is at ~900' surface.

    I think its massively unlike the main spillway end - where the weir is 64' at its base and 60 feet tall, with existing grade at appx 875 on reservoir side (meaning 39' down to base of weir) - that there would be a failure there ... and if one ever looked imminent they'd open the main spillway regardless of the damage below and largely eliminate pressure on the weir
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  22. KenMH

    KenMH Member

    I may be reading it wrong but I feel like you answered a statement I did not make. I asked what the difficulty would be not if it was needed. I suggested that there may be a societal issue with perception of cost of infrastructure. Your answer is directed at dismissing any need to replace a 49 year old concrete structure that has already failed significantly and was built with a lesser understanding of nearly all the issues involved than are available today. while I was not directly addressing if it needs to go, I do not agree with your statements as to why any part of it should be viewed as acceptable risk when a good portion already failed that test.

    To add, it may not be physically possible to replace the main spillway, that is part of the question 'how hard would it be?'. they may need to keep the upper part as functional as possible till a point well in the future when the reservoir is very low before risking taking it out of operation to make any major changes. Don't know, just asking.

    Ed:sorry 49 years not 60+ years
    Last edited: Feb 18, 2017
  23. Scott Gates

    Scott Gates Active Member

    850 is the "flood control" elevation ... their normal drawdown minimum.
  24. Thanks for your post. So if this is the case, that effectively, a "robust" invert elevation is around 900' at the emergency spillway, why don't they just use the emergency spillway again, for a least a short period where they can examine the main spillway again for damage? They must have some real concerns, or they wouldn't be putting all the effort into shoring up the hillside downstream of the emergency spillway. Or is the priority now just lowering the reservoir level to give themselves more flexibility for surges in reservoir inflow? As discussed previously, the primary spillway can only be operated in its current degraded state for a limited period of time, and we don't know if that will extend to the end of this rainy season. Sorry if rambling a bit, just not sure why the authorities don't share your confidence...
  25. Scott Gates

    Scott Gates Active Member

    An exhaustive inspection will be performed ... that will I'm sure include testing and inspection below the remaining spillway panels. I suspect when repairs are done the entire spillway will be necessarily replaced ... minimal addtl costs comparatively and silly to graft a Cadillac onto a 64 Chevy ...
  26. mtchap

    mtchap New Member

    Three good reasons immediately come to mind...

    1) IF a future investigation determines that the underslab drains have substantial rusting or other mechanical failure, then leaving them in place would be inviting a boatload of future structural issues, and the location of those issues (much closer to the release gates) would pose a much higher risk to the integrity of the dam and also to the public.

    2) IF a future investigation determines that the spillway was built on a foundation that was not properly prepared to spec (a situation that is looking more and more likely to me with every passing day), then the proper course of action in those cases is always to tear out the garbage and do it right.

    3) Even though the upper section has not collapsed, it's still a 50 year old construction that's 1/3rd of the way thru it's reasonably expected service life that is showing signs of significant cracking and requiring periods of significant repair and maintenance. As with ALL reinforced concrete infrastructure construction in the world, your options are basically to replace it now or replace it later. Since half of the spillway is already guaranteed to need major reconstruction, then this would seem to be an opportune time to take care of the entire thing.
  27. Mick West

    Mick West Administrator Staff Member

    Here's the lake level for the last two years
    So if they were okay with last year they could aim to draw it down to 750, just to be on the safe side. Of course that would need the power station working, and would take at least a couple of months to get there. I suspect they would want to just keep letting out as much water as possible until may.
  28. mtchap

    mtchap New Member

    Add this as #4 in my post above...I believe that a huge percentage of the expense of any major construction project is the first 10 feet. When adding feet to the project from that point forward, the added cost goes down substantially. Every piece of applicable construction equipment you can imagine will already be on site to rebuild the lower half, which will be an enormous project in its own right.
  29. Scott Gates

    Scott Gates Active Member

    My early opinion is the only realistic option is to make quick short term repairs to the main spillway. Get the breach filled with rock and grout it all in place, and replace the sidewalls temporarily - perhaps set in place engineered manufactured panels or similar short term. Get something that works in a pinch.

    Then build a smaller auxiliary spillway with a control structure on the edge of the parking lot. Add a hardened spillway at least past the parking lot access road.

    Do some geo-testing to determine bedrock in the ravine below the parking lot road. If its bedrock as expected it probably can handle releases from the auxiliary spillway as is, perhaps after removal of surface soils.

    The operating specs can mandate aggressive management of levels of the reservoir to minimize necessary outflows

    Once that spillway is complete the existing main spillway can be rebuilt.
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  30. Tom1

    Tom1 Closed Account

    Are we certain there is high quality rock under the weir's footing for its entire length?

    Comparing the design blueprints and spillway test models posted earlier: the actual photos appear to show deviations.
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  31. mtchap

    mtchap New Member

    I think the only reason they are messing with the emergency spillway at all at this point is because of the small possibility that the main spillway suffers total failure, which is NOT expected by anyone at this time that we know of (other than some zealous youtube users). Anything short of that scenario, and my impression is that they have absolutely zero intention of ever using it again under any other circumstance. HOWEVER...if they do end up needing it again (spring thaw release rates are still to be determined), then there's no chance they will caught with their pants down twice regarding the readiness of the backup. It will be as ready as they have the capability of making it.
    Last edited: Feb 18, 2017
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  32. KenMH

    KenMH Member

    There are 2 dams, one north and one south, that could be opened to release some of the upper lake level. saddle dam locations in GE.

    Nether has a channel designed for it, would be disastrous for the immediate downstream communities, but the option is there to spread the flow to 2 different areas far away from the dam. One would empty into Bidwell Canyon and the other drain south into a creek system. Bidwell Canyon saddle dam foot is apparently at 875 feet in relation to the main spillway, Parish camp foot is at the 895 foot level. According to the Height from base and Crest elevation for both from the following PDF. Both crest at 922 to match the main dam.

    I have no idea if it is at all possible, but the south dam Bidwell Bar Canyon Saddle Dam is to very flat terrain relative to the spillway. It may be totally wrong to do this, it would be essentially the same horrible situation of potential back cut into the reservoir, but if that was actually taking place at the spillway the south saddle dam seems like it would flood the least individual landowners before entering the yuba watersheds management system.

    I wonder if they have ever considered relocating the spillway entirely to one of those more distant saddles below lake level than the one they used next to the dam?

    Also, I got confused in GE as Parish camp Saddle Dam empties into Bidwell Canyon and Bidwell Bar Canyon Saddle Dam empties to the south foothill slopes, creeks leading to the yuba river. It seems a bit odd how they are named but the documents confirm the locations.

    PDF here
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  33. Ethan O'Connor

    Ethan O'Connor New Member

    There's a painting of the dam at the visitor center that appears to show a design with:

    a) The larger, combined outlet works you mention (including concrete apron for what I guess would be proper auxiliary flood control)

    b) An unlined spillway channel

    c) A spillway alignment closer to east-west than the current alignment, proceeding directly down the sub-saddle valley

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  34. Scott Gates

    Scott Gates Active Member

    Current update 2/18/17 16:00 PST:

    Level: 854.07 (drop of 48.51 feet from peak)
    Acre feet in reservoir: 2,863,316
    Inflow: 38,343
    Outflow: 54,987 (They have now reduced outflow to 55,000 cfs)
    Reservoir Capacity: 3,573,577
    Current available storage: 711,261 Acre feet

    Data from Sunday 02/12/2017 16:00 PST:

    Level: 902.09
    Acre feet in reservoir: 3,570,722
    Inflow: 41,410
    Outflow: 65,117
    Available storage: 2,855 ac feet

    Storm total inflow from the January 15" storm event: ~588,369 ac feet (from pint where flow reached 60,000 cfs to went back down to 60,000 cfs inflows). Total storm inflow estimated at appx 670,000 ac feet.


    CA AWR could shut down the spillway entirely right now and have sufficient storage for the entire 15" rain event inflow (assuming 670,000 ac ft) ... elevation would be appx 899.75

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  35. Scott Gates

    Scott Gates Active Member

    The flood control elevation of 850.00 represents appx 2,808,351 ac feet in the reservoir ...
  36. alec

    alec Member

    Hmmn, thanks for posting last year's curve for comparison . Both curves rise steeply. January start points of 2016 v. 2017 reveal (2016 ) 670' initial elevation and (2017) 725' initial elevation . Peak elevation (2016) reached in May. Perhaps representative of spring melt? After many dry years, it's likely they were managing for max capacity. I expect flood control and spillway conservation may produce a different regime this year. Likely, were one to look at longer term records management trends might emerge distinguishing dry years from wet years, likely even high enough resolution to spot large storm events. Somehow , the idea of understanding the unique conditions of a given situation keeps re-emerging as an essential operating foundation,...i.e., where are we now? How to get where we'd like to be from where we are? Personally , I keep getting hammered by that idea , and my thoughts about forcing a situation into a desired theoretical framework rightfully suffer by imposing reality. I'm deeply grateful for the insight, critique , evidence based reasoning, imagery, prints, data, personal experience and understanding you folks have assembled and offered here . The civil tone of it , in today's world , is also welcome. Thank you.
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  37. Ethan O'Connor

    Ethan O'Connor New Member

    Here's a choice quote from this document:

  38. MortarBoarder

    MortarBoarder Member

    Replacing the top of the spillway gives one advantage: the remaining spillway can be examined as it is removed, as well as the rock underneath. That will provide information which can be considered in estimating what happened, and the engineers will know better what they're doing as they put in the replacement.
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  39. mortimers

    mortimers New Member

    It will take a billion dollars and several years for the main spillway or to do the Sierra Club plan and do the emergency also?

    I realize construction costs are exponentially higher now than in the 1960's and they were trying desperately to save the spillway, but if this is something that cannot be accomplished in one dry season, doesn't that mean some serious problems for the future operation of the dam?
  40. Scott Gates

    Scott Gates Active Member

    It is an "emergency" spillway ... they are protecting and hardening it so it is available and safe for use in emergencies. Use of the spillway for significant periods or flows will cause significant downslope erosion and sedimentation into the river ... they could do it but it is not desirable or wise.

    The current spillway has shown no signs of catastrophic failure. It appears to have reached a relatively stable point.

    Construction on the emergency spillway has shown they can do pretty significant repairs in a short period. I have no doubt that within a short time they could fill damaged areas with rock, grout the rock with cement, and either pour a surface, come up with an engineered cement panel solution, or some other method.

    Erecting temporary sidewalls could similarly be relatively quickly accomplished.

    That would get them thru til summer and give them time to develop more permanent plan.
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