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]

Inflow and outflow have reached equilibrium at about 60,000 cfs. Upstream reservoirs are at capacity. Up to 10" of rain is forecast. These are not good things.

 

[azcats]

There have been 90k inflows the last several hours & the lake level is slowly rising.

 

[oldestguy]

itsmoked: Since you are digressing and no complaints appear, maybe you can tell us how's come you picked that handle.

 

[dik]

Since he's electrical... no smoke or sparks; it's a software problem.

Dik

 

[berkshire]

Here is yesterdays update on you tube.
B.E.

You are judged not by what you know, but by what you can do.

 

[oldestguy]

More armchair comments. Noting that there was a geologist way back at the beginning chipping at rock samples and photos showing erodible rock then (at least near the hill surface and likely deeper), and seeing the grid transmission towers placed where the emergency spillway erosion could take them out, and now that they have been disconnected, and hearing that the release of water via the penstocks to the hydro plant, but the hydro generators can't be run due to high tail water and that they must be connected to the grid to be running, and that there is no grid power now to run the spillway gates, this certainly will rate as one of the greatest engineering disasters of all time.

 

[JohnRBaker]

...this certainly will rate as one of the greatest engineering disasters of all time.

If there is no downstream flooding and the public is not seen as being in danger, I really doubt that the average man-on-the-street will agree with you. Granted, among engineers and others like the present company, you might be able to make an argument that it belongs on some list of "Greatest Engineering Disasters" but that will be about it. As far as the media is concerned, as soon as the threat to life and limb was removed, so was their desire to cover the "disaster" since from their point of view, there was NO disaster and therefore NO news.

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

 

[oldestguy]

Mr. Baker you are right, but the general public doesn't read these posts, only engineers. Without that designation,or another designation (medical, human, etc.), it would not fly in general. Regardless, looking back how could such a group of mistakes be made by engineers apparently with so much experience? Politics in the way?

 

[IRstuff]

If it fails entirely, then it probably would exceed all of the other major dam failures in the US combined:

https://www.rt.com/usa/377210-dam-disasters-in-america/

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[JoshPlumSE]

I don't know, I consider this a failure of maintenance as much as anything. Something was going on with the main spillway awhile ago and they didn't fix it. Then when they needed it, it caused severe damage....

But, it was through excellent design of the overall dam system that the severely damaged spill way posed little to no threat to the overall dam stability.

Then the emergency spillway was used in lieu of the damaged spillway instead. Not sure why. Maybe to limit the cost of repairing the damaged spill way this summer.

To me, the emergency spillway is the only thing that shows a true flaw in design. And, that's in a redundant system that was never supposed to be used. Though you could also say that this is something of a maintenance issue as the problem was identified 10 years ago.

Even then a failure of the emergency spillway wall doesn't jeopardize the overall stability of the main dam. It just means that 30 feet or so of water could be released. Enough to cause a major disaster and loss of life, for sure. But, not like what would happen if the main dam itself were to fail.

Overall, there is lots of impressive redundancy engineered into this system.

 

[oldestguy]

The main spillway failed probably due to a very weak zone in the "rock" (look up the geology of Oroville quadrangle A real jumble of different "rocks".). During construction weak zones like that should have been replaced with much harder material, a very common technique. Note the direction of the flow matching valleys in the area as to orientation. Enough erosion of the weaker "rock" traveling up stream is the main concern now at the emergency spillway and could, in time, also take out the gates of the main spillway. After that how long before a new gully forms there in this weak "rock" draining the lake. Redundancy in design maybe, but why the scrambling now? It's a botched redundancy job.

 

[msquared48]

Another point of concern I found out last night.

Apparently the power to the main spillway gates has been cut as the turbines are currently shut down pending debris removal downstream. This removal process necessitated disconnecting the turbines from the power grid, as well as the main spillway gates. So, except for any possible manual manipulation, they are stuck at 60,000 cfs or so for the moment.

Seems to be doing OK for the moment.

Mike McCann, PE, SE (WA)

 

[itsmoked]

oldestguy; I probably shouldn't digress further here. Ask me in the pub sometime.

The power plant and dam still have power as the transmission line running across
the "party area" simply ties two substations together for redundancy and probably
to support summer cooling loads. Hence, they still can run the gates and start the
plant up whenever they can.

I wonder how the two barges and cranes that have been trying to remove the debris
from the tail-water bay are making out. No one ever seems to report on the nitty-
gritty. Someone should have a science reporter tagged to the mess.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[msquared48]

itsmoked:

So are you saying that even with the turbines off line, the gates are able to draw power from another source on the grid?

I understood that the main transmission line from the powerhouse to the switchyard had been disconnected too, creating the situation I described.

There is so much ^&T^ here, I just do not know what to believe anymore.



Mike McCann, PE, SE (WA)

 

[VEBill]

"...should have a science reporter..."

While a few are competent, too many science reporters haven't got a clue.

Excuse the interruption; carry on...

 

[ScottyUK]

msquared48,

It would surprise me that there wasn't in-house emergency generation available to operate safety-critical equipment such as the penstocks, control systems, etc. Being on internal generator power obviously isn't ideal, but a whole lot of things in that plant are a long way from ideal. I'm not from a hydro plant background but internal generator backup is certainly normal with thermal, CCGT or nuclear plants.

 

[dik]

I gathered from the video that they have to rely on emergency standby generation to operate the gates, and this power may not be available. Pretty scary situation. I don't know what's downstream for a substantial distance, but, if it is occupied and the dam fails, there could be a loss of life in the thousands. I pray (and I'm not overly religious) this is not the case.

Dik

 

[JohnRBaker]

To answer a couple of the questions that has been asked...

msquared48 at 21 Feb 17 23:03 wondered about how the spillway gates were being powered. If you go back to berkshire 21 Feb 17 17:33 post and watch the video you'll see where there are emergency generators providing power to the dam and the spillway gate mechanism. This should also answer ScottyUK 22 Feb 17 00:13 question.

As for the questions asked by itsmoked at 21 Feb 17 22:21 the video below should help with that as well as more discussion about the emergency generators and some good video showing the current level of the water in the dam:

https://www.youtube.com/watch?v=Nrz-U1yxOWM

And from what I've seen in his videos, this guy Juan Browne might also answer the issue highlighted by VE1BLL at 21 Feb 17 23:51 when he was asking if there might be a "competent" science reporter around. Now I don't know his background or if he's even an actual reporter, but so far he appears to be doing the job fairly well:

https://www.youtube.com/channel/UCphqjYZxxzjNbONVmY-0J7Q

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

 

[itsmoked]

Thanks John for that YT link. That guy did a great job! I liked it a lot.

About the power, cripes. I watched on TV as an Oroville 'engineer' stated
that the power lines, "Only go between substations and do not affect power
plant operations".

It certainly is hard to see thru all the BS.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[cranky108]

Being from a power background, Portable power units can be rented, so that should not be an issue.

Also, reporters almost always get it wrong when it comes to reporting about the power industry.

Power transmission lines do go from substation to substation, and most power plants have an interface substation. The exception is if the power plant capacity is very small.

Some hydro plants have backup generation that is from the same source as the main generation, i.e. hydro. But if the tailrace level is too high, none of the generation can produce much output.

Assumption: If the main generation can't be used, and it's not from a lack of water behind the dam, then the tailrace water level might be too high. Question: Why is the tailrace water level so high?
Why is the water not flowing downstream?

Another possibility is the transmission lines/towers may have issues. Is it possible some of the transmission towers have been undermined?