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

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msquared48

msquared48

Structural
Aug 7, 2007
14,745

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....
Click to expand...

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

Mike McCann, PE, SE (WA)
 
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The last time the spillway was used to any extent was 2011, but the water level has been past the spillway gate in 3 of the intervening years, during the spring/summer melt, and one would expect that they would have done at least a cursory inspection in each of those years, which includes 2016. What's unusual this year is that the water level hit the spillway by the end of January, which means that this was local rainfall induced, as opposed to snowmelt induced. Therefore, the most likely explanation is the heavy rainfall undermining the spillway, particularly since the spillway surface broke in the first week of February, before the spillway really got much use, so just the 20,000 to 30,000 cft/s flow was enough to break the concrete, which ought not have happened without undermining of the ground underneath.



It's actually trivial to reject proposals; we recently got rejected because of a nitnoid in the presentation of a part of the cost data. That could have likewise been trivially
fixed, had the customer been interested in keeping us in the competition. Any halfway decent boilerplate will have lots of opportunities to miss a requirement that can get you rejected.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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In one of the movies shown by Juan the-777-longhaul-pilot the concrete looked to be pretty thin in the
area it failed. Everywhere else it was about 3 feet thick but right-of-center it looked to be only about
half that.

Keith Cress
kcress -
 
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dik, sure jhardy's approace is much better than lower price. And given that some aspects of 'better value' can be subjective is probably the best you can hope for in many circumstances.

Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​
 
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Seems to me that the thickness variation is simply a reflection of the fact that the hillside wasn't level and couldn't be made level, so the concrete was simply poured to level out the hill. The fact that parts of the hillside that are severely washed out, but were the last parts to lose the concrete says that any water intrusion under spillway was likely to essentially create sinkholes.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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IRS Stuff:

Note that the side wall discharges from the under-slab herringbone drainage system ran pretty full. The crappy sections of "rock" under easily eroded from seepage water that leaked down through the many cracks and joints. Note now they are trying to seal those cracks., More band-aid type repairs rather than a full replacement and correction of the poor zones underneath.
 
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Juan(Browne)-the-777-Pilot also moonlights at a local civil engineering firm so he knows what he is looking at, what to look for and what questions to ask. I really appreciate his perspective on this thing.
 
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My 2 cents.
Two issues I have with this design or rather, end product. sometimes the design and end product separate paths due to financial issues.

The emergency spillway seems to be more or less at the same height as the whole area where the parking area is. What bothers me about this.?

1. Whatever water flows downhill in a uncontrolled way, will cause erosion parallel to the mount of water and time period.It is as if somebody decided that there will never ever be a need for water to flow over it. Big mistake when it comes to us nature of harnessing nature. If you do not plan and most important,spend good money on your idea, nature will win,time and time again.

My solution, lower the emergency spillway be two or three feet and side channel it into the main shute. Unless they apply cosmetics all the way down, this will cause problems, if not serious corrosion,still mud into the river,oh,then they need to catch all the fish below again to save them.:))

Main shute. Two issues I have. Not so much volume but the change in angle halfway down. Use specialized methods and remove some of the rock formations, reduce the curve radius, pay attention to energy dissipation and create a proper still basin that do not obstruct the flow from the powerhouse if max water is released.

Will still be miles cheaper then all the money this issue cost up to now,and which can and will repeat itself with their band-aid repairs(quote toe word from a previous poster who nailed it).
Lets just take the evacuation in its own. The loss of income and all other issues and expenses.
 
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From WIKI:
"Stepped spillways, consisting of weirs and channels, have been used for over 3,500 years since the first structures were built in Greece and Crete...........
Although the stepped spillway design was common up to the beginning of the 20th century, a lot of expertise has been lost since, and the present expertise is limited to very simple geometries, namely some flat horizontal stepped prismatic chutes, despite some recent interest in stepped spillway design."

Those who do not learn the lessons of history.........

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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another 2c or 1-1/2 CAN:

Water flowing over a lip will create a certain curvature determined by gravity. My understanding, from earlier hydrology courses, was that the shape of the concrete spillway should mimic a curve equivalent to 0.8 to 0.9 of the gravity value to ensure that the water has a direct positive bearing contact with the concrete and cavitation is avoided. Alternatively, the spillway should have energy absorbing blocks to create turbulence. (Caveat - did all my undergrad work in hydraulics, but, have not worked in that field).

Dik
 
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They fired up the spillway again yesterday and plan to run it for three to four days. Great video of the restart here with other updates:

Some highlights. They can only operate at 40,000 to 50,000 cfs now. Less than that and they have too much headcutting. More than that and well...

They shored the whole thing up with grout, crack sealing, and rock bolting. The latter focused on stabilizing the left wall which had started to show some movement.

They have a burn rate right now of about five million dollars per day.

They are evaluating two alternatives for the long term repair, and have already mobilized rock crushing and concrete batch plants. They expect to have a design finalist in two weeks. The new spillway may have much less capacity which will limit their ability to use the reservoir for water supply.

The power plant has to be taken offline during spillway operation as the tailwater still rises too high.

They expect to have 3-4 more releases like this over the course of the spring.
 
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Now maybe they are starting to9 do things right. A small length core (maybe 5 feet) as visible in the storage box (yesterday photo) show pretty crappy looking stuff. Could this be interpreted that the full length of spillway will get replaced on top of corrected support by hard material rather than rotten rock? The core location appears to be on higher ground, possibly near the inlet gates. Getting rock cores for the full length of the spillway should have been a complete job way back when things were built. Better late than never.
 
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Oroville reservoir dynamics in a nutshell: [URL unfurl="true"]http://cdec.water.ca.gov/river/res_ORO.html[/url]

Looking at the top left graph of ORO inflow can anyone explain to me how these major daily fluctuations occur? I can only
imagine one slow increase/decrease over 24 hours and don't know why there would many large excursions a day. I don't
recall ever seeing a river flow go up and down 400% several times a day.

Keith Cress
kcress -
 
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I haven't looked at the data, but an upstream hydro plant would be an easy explanation. There's a wide range of water flow from plants that aren't run as run-of-river. I've even seen advertisements for a white water adventure on some river back east the seems to be timed to the afternoon ramp up of one or more hydro plants.
 
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I would think that it's the same sort of noise issue as the other measurement you mentioned a couple of weeks ago. Note the negative flow excursions on this one as well.
The long graphs show what the general trends look like:

The graph your link pulls up is a 24-hr graph. The daily flows show fairly consistent behavior:

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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hmmm. Interesting.

I'm realizing that it's not just the Feather River but actually the Feather River and several tributaries all
running thru the Sierras that add to make the flow reading. I'm thinking the daily warm up / freeze down would be
affecting all the various tributaries at pretty much the same time every day but the actual time the water takes to
travel the hundred mile type distances could have a prior high flow at a particular drainage showing up many hours
later causing various staggered patterns at the near reservoir flow sensor.

Keith Cress
kcress -
 
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davidbeach - I was over in Tennessee a number of years back and went white-water rafting on the river you're talking about, the Ocoee River. It's the same river where they ran the kayaking events for the Atlanta Olympics.

I was in the very first group in the morning and we had the strangest experience. When we pulled up to the river to get into our boats, the river was raging like any other whitewater rafting river. As we paddled downstream everything seemed normal, but when we rounded one of the river bends we could see the entire downstream river bed was bone dry. We had caught up to the leading edge of the water flow! We had to pull into an eddy for about 15 minutes before we continued down the river. We had to do this about 3-4 more times during our run as we kept catching up to the flood.

Fun river otherwise, just a strange experience.
 
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Here's a link to a 'live' webcam from the Oroville Dam:


I realize that I'm posting this while the sun has just set in Northern California but perhaps tomorrow morning it will be worth watching.

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
 
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