Oroville Dam Spillway Concrete Failure (Feather River Flooding, CA) 36

[msquared48]

http://www.msn.com/en-us/news/us/ga.../ar-AAmLuQj?li=AA4ZnC&ocid=spartandhp#image=1

Erosion has created a 300-foot-deep hole in the concrete spillway of Oroville Dam and state officials say it will continue grow.
State engineers on Wednesday cautiously released water from Lake Oroville's damaged spillway as the reservoir level climbed amid a soaking of rain.

Situated in the western foothills of the Sierra, Lake Oroville is the second-largest manmade reservoir in California after Shasta....

Member Spartan: Stage storage flow data here for those interested:

https://cdec.water.ca.gov/cgi-progs/queryF?s=ORO

Mike McCann, PE, SE (WA)

 

[Spartan5]

I would really like to see some facility drawings on the project. For the emergency spillway to function without failure, it had to be designed for overtopping. What is the maximum design lake level though, and that been exceeded?

Some really great information in this document here:

http://yubariver.org/wp-content/upl...lub-SYRCL_Oroville-Dam-Joint-Intervention.pdf

SHOCKED to learn that they had planned in the course of normal flood control operation to allow for water to surcharge 10' higher than the top of that emergency spillway and they they could take it up to 16' in an emergency!! Decorum be damned, WTF???

Look at what happened when they allowed a 2' surcharge

 

[cranky108]

As someone who has worked in micro amps and Kilo amps, it is hard to get your mind wrapped around the sizes of things. But the only differences in the calculations is the qualifier (Pico, micro, kilo, mega, giga).

But I do admit that I have never seen our civil engineer work with tea spoons.

Sometimes it helps to look at what your working on so you get a since of scale.

 

[LittleInch]

dgallup. Think of this in units you can understand works for me.

1200 tonnes of rock equates to around 50 trucks - so around 1 per minute.

To be fair that's a lot of trucks and not sure if they meant 1200 tonnes per day.

The choppers can't carry much , maybe 2-3 tonnes and cycle time is quite long so the heavy lifting is being done by the trucks.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KENAT]

dgallup - the images I saw looked like Sikorsky S-70 family so depending on what exact mark the external load could be up to 9000 lb - I don't know the elevation of Oroville I'm guessing not high enough to decrease that much.

If they were serious they'd be borrowing some CH-53's from the Marines, if any of them are currently air worthy that is.

Posting guidelines faq731-376

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(probably not aimed specifically at you)
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[MacGyverS2000]

Sometimes it helps to look at what your working on so you get a since of scale.

Like dg, I work at the micro scale when it comes to PCB design... once in a while I need to actually pull a board out to remind myself how small those features I'm designing with actually are compared to what I see on the monitor. Helps to avoid mistakes when you remember how big/small something actually is.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[azcats]

For the first time in several days, they've just started ticking down the main spillway. It's been right at 100k since sometime on the 12th. 97k and 95k in the last two hours.

Link

 

[msquared48]

Well, they have drawn it down about 35 feet and increased the available storage capacity for the new storms to about 55,000 acre feet before elevation 902.5 is realized again that was seen on Saturday.

The reduced flow may not be by partly closing the gates, but by the reduced head behind the gates...

I wonder what the elevation of the main spillway is?

Mike McCann, PE, SE (WA)

 

[azcats]

Link

"At the same time, the Department of Water Resources announced it was reducing flows down the dam’s main spillway as crews get ready to remove the large volume of debris that has fallen into the channel below."

I couldn't find (in my admittedly brief search) info on the gate elevation.

 

[itsmoked]

At the Diversion Pool, heavy equipment and barges are removing the debris
that has piled up at the bottom of the main spillway. The debris has raised the level of the
pool to the point the Hyatt Powerhouse can’t be used.

If the powerhouse were in operation, another 13,000 cfs could be drained from the lake.

PG&E is also at work, moving some transmission line towers from below the emergency spillway,
in an area that could theoretically flood if that spillway were to be brought back into use.

Ouch! More insult to the dam.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

According to the document referenced by Spartan 5 the bottom of the main spillway gates is 90 feet below the top of the emergency spillway.

Interestingly this also gives section details of the spillway - looks rather simple to me.... No wonder they were worried. The section is noted later as being in the middle of the emergence spillway.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Spartan5]

The elevation of the crest of the main spillway is 811' per page 6 of this document:

http://yubariver.org/wp-content/upl...lub-SYRCL_Oroville-Dam-Joint-Intervention.pdf

 

[Spartan5]

JINX!

 

[LittleInch]

SNAP!

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[itsmoked]

Mutual assured confirmation!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[msquared48]

WOW!
90 feet of head on a 33 foot high Radial Gate.
These must be some honkin' gates!

At elevation 855 or so where they are now, they still have 44 feet of head on the 33 foot gates.

You'd think that they have some lower sluice gates they could open too, but maybe not.

Mike McCann, PE, SE (WA)

 

[JohnRBaker]

BTW, here's what the spillway looks like from the inside of the dam, taken obviously during dryer times:

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[jraef]

As to the questions about why wasn't it brought up earlier, it was. 12 years ago, when three groups of "tree huggers" (Friends of the River, the Sierra Club and the South Yuba Citizens League) predicted this in a report they prepared for re-licensing by FERC, the Army Corps of Engineers and the California Dept. of Water Resources. They called for the concrete paving of the emergency spillway, saying it could not be used as designed. But in all the efforts at the time to reduce government spending, the entire dam was declared perfectly safe and fine, so no need to spend one dime on it. At that time it would have cost roughly $100 million, now it's going to be 3x that much.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[BigInch]

It would appear that they were right. An expensive lesson in pay me now, or pay me later. Delay is usually counterproductive on all fronts, here very much so.

Reaction to change doesn't stop it

 

[hokie66]

I see the primary spillway as the first priority. Then the auxiliary spillway, which actually did its job, albeit with a lot of erosion.

 

[oldestguy]

Assuming we, in our armchairs, are right and at least as I view things, the metamorphic rock under the main spillway will, from time to time, lose material from weak zones and erode, resulting in everyone scurrying around to "fix" them, I wonder if now might be the time to seriously consider abandoning the whole dam and its lake. etc. Perhaps placing this dam and its spillways where the rocks are not the best for this use was a mistake to begin with. This is question that certainly should be considered as repairs or upgrades are considered. If no abandonment, will the fix take some form of cementing the rock under that spillway (and maybe the emergency one also) so that erosion in the future is "assured" to never happen? Costs for that treatment likely will be very difficult to justify. There is a post elsewhere providing pretty good geologic information, including signs of faults near the dam itself. A post on another web group shows an old photograph of the excavation for the main spillway with "rock" being loosened with crawler tractors pulling a two teeth ripper. That's pretty damming info. Even photos now close up show the rock in pieces, not cemented together and deeply eroded zones apparently even weaker. A common construction technique when questionable material is found under a structure is replacement with much better material, such as concretes. At this site, is this even possible if most of the stuff needs replacement by this rule? and how deep?