Oroville Dam Main Spillway Waterfall Erosion Watch

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aczlan said:
It is not like they have been able to get close without risking getting washed downstream or sliding down the hill.
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I disagree. There is a DWR drone video from the 18th that comes so close to giving a good shot at both the minute mark and at 1:26, but cuts out right before. You can see from the distance that the erosion on the 18th wasn't that far up toward the power pole, but why not just show it clearly? Surely they ran the drone up there...

Screenshot at 1:26

Full DWR drone video 2/18/17:
Source: https://youtu.be/yxgtyOfwrj8
Screenshot_2017-02-21-19-46-58.png
 
deirdre said:
i guess we'll know when the outflow stops just how bad they 'were scamming' the public, right?
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I wouldn't go so far as to say I think they're scamming the public, but it is certainly a poor move from a PR standpoint. Especially for a department that said they didn't expect water to go over the emergency spillway only to have it go over hours later. There is definitely a level of distrust from the public, one would think they would attempt to be less opaque.
 
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Anna Reynolds said:
There is definitely a level of distrust from the public, one would think they would attempt to be more opaque
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i guess. and i do know that when i'm interested in a subject it always iritates me that there isnt constant footage, so i hear you.
But i do personally think if the hole was breaking further up the spillway we would see evidence of that from erosion on the side (which is the point of this thread) and they would probably move those power line towers like they were planning to do.

I'm very curious to see what everything looks like too once the flow stops too.
 
Marian said:
I live at ground zero. The lack of good up-to-date visuals of the state of the erosion is very frustrating and nerve-wracking.
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Hi Marian. I've been thinking that we're all going to be depending upon your local neighbors (with drones) to be providing updates throughout the entire reconstruction process. If you discover that happening, please announce it here.
 
whoosh said:
Hi Marian. I've been thinking that we're all going to be depending upon your local neighbors (with drones) to be providing updates throughout the entire reconstruction process. If you discover that happening, please announce it here.
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I live just a few blocks away, once the flight restrictions are lifted I'll have some drone video, I'm dying to get one of my fixed wings up.
 
Lisa said:
This first pic is excellent, as you can actually see the jagged outline of the slab as the water is falling over it. Great for discerning even minute changes if we get a future pic taken from the same angle. :)
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It is. The right spillway wall looks to be leaning towards the flow. If so, there could be slab separation. I don't recall seeing that in previous photos, but it could just be the perspective.

upload_2017-2-24_11-32-46.png


It is certainly not evident in this photo, but that was a long time ago:

http://pixel-ca-dwr.photoshelter.co...g/KG-oro-spillway-damage-10504-02-09-2017-jpg

upload_2017-2-24_11-53-22.png
 
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CRM114 said:
It is. The right spillway wall looks to be leaning towards the flow. If so, there could be slab separation. I don't recall seeing that in previous photos, but it could just be the perspective.

upload_2017-2-24_11-32-46-png.25452
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I think that's just a combination of the curve of the spillway, perspective (wide angle lens) and the broken end of the wall normally leaning downslope. Here's a Google Earth pic from a similar viewpoint
20170224-112332-yn4ky.jpg
 
upload_2017-2-24_11-32-46.png


Looking at the shadow, it does look like it is leaning in. I think if the wall was angled down, following the curvature of the hill, the shadow would be shorter.
 
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The shadow and the wall curve match the pre-collapse angle of the wall as seen in Google Earth.
20170224-114206-zkby3.jpg


Again, it's hard to detect changes in a photographs if you can't compare like with like. Different view positions and focal lengths (camera zoom) can have a huge and unintuitive effect on how something looks.

So please try to limit interpretation of images to those images where you can do a comparison (even if it's only a Google Earth comparison).
 
Mick West said:
I think that's just a combination of the curve of the spillway, perspective (wide angle lens) and the broken end of the wall normally leaning downslope. Here's a Google Earth pic from a similar viewpoint
View attachment 25462
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upload_2017-2-24_12-33-46.png

I see what you mean. It's tough to tell. I added some lines for reference. I tried the same on your google pic, but it's sketchy to pick the top of wall.
 
Stack Dump said:
In that last picture (post #192), it doesn't look like the wall is leaning.
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I don't think it's leaning either but the issue whether it might be leads on to some further consideration of why the upstream erosion has been very limited over the last two weeks.

The photo in post #192 is the only one I have seen which shows an intact area of spillway side wall beneath the adjacent ground and it looks to comprise no small amount of structure, which it's possible to see in this close-up:

View attachment 25488

The depth below ground level looks to be at least 4x the height above - probably about 6 feet at this point judging by the generator in the foreground and other photos showing DWR staff standing next to the wall. This is consistent with the description given on p. 100 of the 1974 DWR account of the design and building of the dam and related facilities:

View attachment 25493

I admit that when I first read this I (mis-)understood it to mean that the side walls extend deep enough underground actually to be set into the foundation material; I also did not pick up exactly what "structurally independent" might mean. The cantilever design referred to is basically an L-shape construct laid directly on top of the foundation material:

View attachment 25501

The drawing shows what are described as "typical" cross sections of the chute. Consequently I don't want to read too much into what they show but for a section of the side wall to be leaning over into the chute it would have to be rotating against its own footing. That seems improbable unless the footing has been destroyed but in that case the wall would likely have collapsed.

From pictures posted earlier on this and related threads, including those in post #175 above, by 9 February the critical defect in the main spillway had been exposed and appears to be the result of a section of it bridging an area of inadequate foundation material. That much really seems to be obvious. If there is more of the same further upstream or down it seems likely some sign of it would have appeared by now.
 
Per BCSO outflows will start to ramp down around 6:45AM tomorrow eventually to 0. Hopefully we'll see some good pictures from DWR

External Quote:

SPILLWAY PRESS BRIEFING ON REDUCED OUTFLOWS TOMORROW MORNING AT 10:00 AM

Oroville, California - Tomorrow morning at 6:45 AM, the Department of Water Resources (DWR) will begin gradually ramping down outflows from the Oroville Reservoir. Flows from the flood control spillway will be reduced from 50,000 cubic feet per second (cfs) throughout the day and eventually reach zero in the afternoon.

As flows are reduced, DWR will monitor the status of the dam, spillways, and related structures to ensure their continued safety and stability. Flows will be reduced gradually to minimize risk to downstream levees. Through use of water stored in the Diversion Pool and Thermalito Forebay and Afterbay, flows necessary to meet fishery requirements in the Feather River downstream of the dam will be maintained.

Cutting off flows from the flood control spillway for several days will allow workers to aggressively attack the debris pile at its base and reduce the water level surface elevation of the channel that leads from the Hyatt Power Plant.

Removal of debris will help safeguard Hyatt Power Plant and allow for its eventual reoperation. Once operational, the Hyatt Power Plant can discharge roughly 14,000 cfs, which will allow DWR to better manage reservoir levels through the remaining spring runoff season.

Since February 12th, DWR has reduced water levels in Lake Oroville from 901 feet elevation to 842 feet, nearly 60 feet below the top of the emergency spillway. With current outflows at 50,000 cfs and inflows at only 25,000 cfs, the department will continue to create even more space in the reservoir throughout the day and overnight.

DWR Acting Director Bill Croyle and Butte County Sheriff Kory Honea will discuss these plans to reduce flows at a press briefing tomorrow morning, February 27th, 2017 at 10:00 AM. It will be held at the DWR Oroville Field Division, located at 460 Glen Road in Oroville CA 95966.

For those unable to attend, a conference line has been established. Please call (866) 508-9046 and enter the following code: 5743919. This is for listening purposes only. No questions will be taken over the conference line. The press briefing will also be streamed on DWR's Facebook page.
https://www.facebook.com/bcsonews/posts/789204901229790
 
Marian said:
http://pixel-ca-dwr.photoshelter.co...I0000yYFnwfD7v7Q/KG-oroville-damage-14319-jpg

From CDWR today. The flow pattern has changed, very little water is now going down the bottom of the spillway.
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Thanks for posting this. It suggests that the flow out of the reservoir might have decreased even before the flood control structure is used to ramp it down. From the image it appears that there are two main areas of spillway collapse up- and downstream of a natural rock outcrop under the spillway deck. Will be interesting to see how deep the "cavities" are in those locations - to say nothing of what might be done to bridge or indeed use them in any repair effort.
 
deirdre said:
i guess. and i do know that when i'm interested in a subject it always iritates me that there isnt constant footage, so i hear you.
But i do personally think if the hole was breaking further up the spillway we would see evidence of that from erosion on the side (which is the point of this thread) and they would probably move those power line towers like they were planning to do.

I'm very curious to see what everything looks like too once the flow stops too.
Click to expand...

I have been very pissed off by the previous constant hiding of the upper part of the spillway above the hole; as a professional (geologist) I would like to be able to see the whole area to be able to make further intelligent comments; the obvious scouring of the weaker hydrothermally altered bedrock indicates local weaknesses that had been ignored by the constructors years ago (perhaps they were over-optimistic), but to prepare for the rebuild the more expert comment that can be made should lead to a more satisfactory spillway being built. The patchy nature of the surface rock would suggest need to remove altered rock and backfill with concrete.

But I must say that the recent video ( https://www.youtube.com/watch?v=m9ar73kBlWg) does show that there has been little progression towards the head of the spillway, which tends to indicate sound bedrock above the problem area.
 
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Boilermaker said:
Thanks for posting this. It suggests that the flow out of the reservoir might have decreased even before the flood control structure is used to ramp it down. From the image it appears that there are two main areas of spillway collapse up- and downstream of a natural rock outcrop under the spillway deck. Will be interesting to see how deep the "cavities" are in those locations - to say nothing of what might be done to bridge or indeed use them in any repair effort.
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I believe the output is still 50k CFS. The difference in flow at the bottom is likely do to different velocity. The water leaving the reservoir is now under less pressure since the level has dropped. Water is no longer squirting out, but rather flowing out.
 
deirdre said:
i do know that when i'm interested in a subject it always iritates me that there isnt constant footage, so i hear you.
Click to expand...

Oh yeah! Some time sinks are just so beautiful, like watching cicadas break out of their shells, or even the Oroville webcam showing the surges of spray above the spillway failure.

Marian said:
I live at ground zero. The lack of good up-to-date visuals of the state of the erosion is very frustrating and nerve-wracking.
Click to expand...

That's why we depend upon you locals, Marian :) If anybody could set up a live feed across from the spillway to watch the waterflows (especially today as they ramp down to zero), and the debris removal from the diversion pool, it would be awesome. Personally, I'd expect DWR to want that footage in their files.
 
whoosh said:
That's why we depend upon you locals, Marian :) If anybody could set up a live feed across from the spillway to watch the waterflows (especially today as they ramp down to zero), and the debris removal from the diversion pool, it would be awesome. Personally, I'd expect DWR to want that footage in their files.
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The trails across from the spillway are blocked off and last I knew only people with press passes have been let in. DWR has a mobile surveillance unit across from the spillway with 4 or 5 cameras on it, I haven't seen any video released from it, however.
 
Blaise said:
I believe the output is still 50k CFS. The difference in flow at the bottom is likely do to different velocity. The water leaving the reservoir is now under less pressure since the level has dropped. Water is no longer squirting out, but rather flowing out.
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Thanks! You put into words what I like to believe I was really thinking.
 
Blaise said:
I believe the output is still 50k CFS. The difference in flow at the bottom is likely do to different velocity.
Click to expand...

50,000 cfs stands for 50,000 cubic feet per second which is a measure of velocity. As water level drops and pressure behind the gates reduces they do adjust the opening size to maintain velocity. I suspect these adjustments at the gates affect the flow pattern as water runs down the chute and could contribute to the apparent lack of water down the main chute even as cfs was reported as relatively stable.
 
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