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Oroville Dam in danger of failing
Old 02-12-2017, 06:50 PM   #1
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Oroville Dam in danger of failing

This is hard to believe. The main spillway couldn't handle the pressure of a designed release, and failed dramatically. Now the auxiliary (emergency) is operating, and not well. Same issues with concrete not being able to take the pressure. In desperation, they are now releasing as much as they can onto the damaged spillway. It is really bad news as undermining is occurring on multiple fronts.

How does this happen? I know the structure design is 50 years old, but come on. Floods are well known in CA history. They knew this kind of flooding happens frequently enough. And now it can't handle it. Scary.

Here in NC we had similiar spillway failures recently with Hurricane Matthew, but these were on private small lakes. Not a major flood control and generating public project!

Prayers and good thoughts to all those possibly affected. Be careful out there.

BREAKING: Marysville, Yuba County evacuated as Oroville spillway collapse feared | The Sacramento Bee

The Butte County Sheriff’ Office released the following statement on Facebook:

This is an evacuation order.

Immediate evacuation from the low levels of Oroville and areas downstream is ordered.

A hazardous situation is developing with the Oroville Dam auxiliary spillway. Operation of the auxiliary spillway has lead to severe erosion that could lead to a failure of the structure. Failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville. In response to this developing situation, DWR is increasing water releases to 100,000 cubic feet per second.

Immediate evacuation from the low levels of Oroville and areas downstream is ordered.

This in NOT A Drill. This in NOT A Drill. This in NOT A Drill.

Read more here: BREAKING: Marysville, Yuba County evacuated as Oroville spillway collapse feared | The Sacramento Bee
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Old 02-12-2017, 06:57 PM   #2
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How awful! My thoughts are with the residents of Yuba City, Marysville, and other communities that are in danger.
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Old 02-12-2017, 07:09 PM   #3
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Wow. This is a big deal. Hopefully, the evacuation goes well and losses are minimized.

https://en.wikipedia.org/wiki/Oroville_Dam

Quote:
Oroville Dam is an earthfill embankment dam on the Feather River east of the city of Oroville, California in the United States. At 770 feet (230 m) high, it is the tallest dam in the U.S.[7] and serves mainly for water supply, hydroelectricity generation and flood control. The dam impounds Lake Oroville, the second largest man-made lake in the state of California, capable of storing more than 3.5 million acre-feet (4.4 km3),[8] and is located in the Sierra Nevada foothills east of the Sacramento Valley.
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Old 02-12-2017, 07:16 PM   #4
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I just returned to the Sacramento area this evening, from the Bay area. I saw lots of flooding between Lodi and Sacramento on both sides of HWY 5. And we have 24 more hours of flood warning unrelated to the Oroville dam situation. Just because of the warm weather and lots of water coming from the higher country. Scary stuff.

The Folsom dam has been releasing lots of water daily for a week or two, in order to keep the water level down to accept all the runoff that is coming.
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Old 02-12-2017, 07:25 PM   #5
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I was looking on Google Earth, and there are pictures of the back side of the auxiliary structure. Because the drought has been so extensive, people were walking on dry earth behind the structure and taking pictures. It is huge!

It puts into perspective just how much the lake has risen, and how much of a flow there will be if this structure fails.

The good news is that the actual earthen dam should be OK. It is just this structure that may go, and if it does, a quick burst of water will follow until it finds level. Hopefully, the bedrock under the spillway can hold up enough should a failure occur.

The pictures and movies of the main spillway are amazing. When it started to fail, some movies caught the point when the water was undermining and throwing chunks of concrete. Water is a powerful force. When that happened, they backed off the flow to try to stem the damage to the spillway. Now that the aux is having issues, they just put caution to the wind and have turned up the main spillway to max, huge crater and all. It's crazy stuff. Water is flying everywhere inside and outside the spillway, chewing up the earth.

This is going to go into the engineering textbooks along with the Tacoma Narrows and Kansas City Walkway disasters.
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Old 02-12-2017, 07:34 PM   #6
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Wow. What a disaster. Hopefully the situation will not get worse while the lake is drawn down to the point where work can be done to fix the problem. And hopefully rains don't increase to the point where water coming into the lake exceeds the 100,000 *** that they currently letting out.
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Old 02-12-2017, 07:39 PM   #7
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Quote:
Originally Posted by JoeWras View Post
...

This is going to go into the engineering textbooks along with the Tacoma Narrows and Kansas City Walkway disasters.
It sure is bad, but not compared to another textbook dam issue:

https://en.wikipedia.org/wiki/Banqia...qiao_Dam_Flood
Quote:
A 2005 book compiled by the Archives Bureau of Suiping county reports that more than 230,000 were carried away by water, in which 18,869 died.[9] It has been reported that 90,000 - 230,000 people were killed as a result of the dam breaking.
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Old 02-12-2017, 07:51 PM   #8
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I was struck by how steep and straight the spillway was. I would've expected a more gradual slope. Until root cause of failure is known I wouldn't put this in the category of engineering failures like a Tacoma Narrows.
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Old 02-12-2017, 08:38 PM   #9
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It's not the dam that is failing, but the spillway.

The water level has risen from 1.5 million acre-feet on Dec 1, 2016 to currently exceeding the 3.5 million acre-feet capacity of the reservoir.

From a drought to a deluge in 2 months!
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Old 02-13-2017, 06:04 AM   #10
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OK, OK. I've woken up my engineering friends to a healthy discussion.

Quote:
Originally Posted by ERD50 View Post
It sure is bad, but not compared to another textbook dam issue:
https://en.wikipedia.org/wiki/Banqia...qiao_Dam_Flood
Hopefully, whatever happens will have zero cost of lives. Not comparing human tragedy, but rather design mistakes. I'm talking about the failure of the spillway for designed flows. How did this happen? Did the concrete change over the last 50 years? Did water exploit small fissures that were undetected or blown off? Etc.

And if the "emergency" spillway goes, how was something designed for an emergency make a worse emergency>

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I was struck by how steep and straight the spillway was. I would've expected a more gradual slope. Until root cause of failure is known I wouldn't put this in the category of engineering failures like a Tacoma Narrows.
OK. It will still go in someone's textbook. You are right, T.C. was problematic from the start. It was outright wrong. KC Walkway was, how shall I say, just stupid.

I think the problem here is the spillway design, as you mention. Something over the 50 years reduced its reliability for high flows that are within the designed range. My guess is this will go in the textbooks under the "concrete" chapter. My civil eng friends can talk about concrete for days on end. They'll be talking about this one.

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Originally Posted by NW-Bound View Post
It's not the dam that is failing, but the spillway.

The water level has risen from 1.5 million acre-feet on Dec 1, 2016 to currently exceeding the 3.5 million acre-feet capacity of the reservoir.

From a drought to a deluge in 2 months!
Right. Spillway is already complete toast. Now they are worrying about the overflow auxiliary too. The actual dam is in fine shape. But if the aux goes, the lake will be drop down (and fast) to the sill level that the spillways are built on.
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Old 02-13-2017, 06:54 AM   #11
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It's been quite a while since I had to study rudimentary dam and spillway design in college; however, I would guess cavitation was involved. Cavitation is the bane of spillway design. It is a well known phenomenon in water hydraulics and is extremely powerful force that can erode concrete under the proper conditions.

Here's a short description of cavitation from a U.S. Department of Interior and U.S. Army Corps of Engineers chapter from their dam safety book on spillway cavitation:

"Cavitation is the formation of vapor cavities in a liquid. Cavitation occurs in high velocity flow, where the water pressure is reduced locally because of an irregularity in the flow surface. As the vapor cavities move into a zone of higher pressure, they collapse, sending out high pressure shock waves. If the cavities collapse near a flow boundary, there will be damage to the material at the boundary. Cracks, offsets and surface roughness can increase the potential for cavitation damage. The extent of cavitation damage will be a function of the cavitation indices at key locations in the spillway chute and the duration of flow."

The following link containing the above explanation will give you more information than you will ever need - or want - to know on spillway cavitation: https://www.usbr.gov/ssle/damsafety/...3-20150610.pdf

This is why I ended up in the 'soft side' of engineering (conducting studies and interpreting regulations) rather than actual design work
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Old 02-13-2017, 07:02 AM   #12
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Statics and dynamics. Ugh. Me too. I considered Civil or Mech, but decided that computers were my thing instead. It doesn't get any softer. Most days I say we are not real engineers, and I tip my hat to those who do design real structures that millions of people depend on to be safe.

This article says the auxiliary was only at 5% of design capacity before it was showing stress. Wow, that's a real design failure. The latest is that opening up the flow on the damaged main spillway has stopped the flow on the auxiliary. Things may turn out somewhat OK. Time will tell, and it depends on the forecast too.

Oroville Dam: Feds and state officials ignored warnings 12 years ago

Quote:
On Sunday, with flows of only 6,000 to 12,000 cubic feet per second — water only a foot or two deep and less than 5 percent of the rate that FERC said was safe — erosion at the emergency spillway became so severe that officials from the State Department of Water Resources ordered the evacuation of more than 185,000 people. The fear was that the erosion could undercut the 1,730-foot-long concrete lip along the top of the emergency spillway, allowing billions of gallons of water to pour down the hillside toward Oroville and other towns downstream.
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Old 02-13-2017, 08:13 AM   #13
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The Oroville Dam was completed in 1968, which makes it a pretty new dam. Few major river dams have been built in recent decades due to envirornmental issues lie snail darters and fish migration. (Oroville would never be allowed to be built today.)

Wikipedia has a plain English up to date explanation on what's going on at Oroville. The secondary spillway is higher than the primary spillway, and it's never even been used. It's pretty interesting reading.
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Old 02-13-2017, 08:40 AM   #14
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KCRA.com is the local news station with a helicopter. They should be posting some current video today showing the hole in the emergency spillway and the helicopters dropping the bags of rocks to try and plug the hole. They hope to stop releasing water from the main spillway as soon as the water gets lower, so they can review the damage to the spillway.

Lots of work going on today, with another storm coming Wednesday night.
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Old 02-13-2017, 09:02 AM   #15
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Quote:
Originally Posted by KB View Post
They hope to stop releasing water from the main spillway as soon as the water gets lower, so they can review the damage to the spillway.
As of last night, the plan is to drop the lake level 50 feet. If the auxiliary spillway fails, the current estimate is 30ft of lake would exit pronto.
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Old 02-13-2017, 09:15 AM   #16
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Quote:
Originally Posted by ERD50 View Post
It sure is bad, but not compared to another textbook dam issue:

https://en.wikipedia.org/wiki/Banqia...qiao_Dam_Flood

Quote:
A 2005 book compiled by the Archives Bureau of Suiping county reports that more than 230,000 were carried away by water, in which 18,869 died.[9] It has been reported that 90,000 - 230,000 people were killed as a result of the dam breaking.
-ERD50
Yet, the Banqiao reservoir capacity is only 400,000 acre-feet. The Oroville Dam holds back 3.5 million acre-feet, or 9 times more.
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Old 02-13-2017, 09:20 AM   #17
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As of last night, the plan is to drop the lake level 50 feet. If the auxiliary spillway fails, the current estimate is 30ft of lake would exit pronto.
On the news, they just said it would take 6 days to lower the lake level 50 feet at the 100 *** they are using. And with more rain expected in a few days, that would be a challenge. I imagine the engineers are busy today, trying to figure out all the repairs and how to manage the water.

They have a team of helicopters starting to move the huge bags of boulders into the hole in the emergency spillway. That footage should be fascinating.
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Old 02-13-2017, 10:10 AM   #18
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I do not understand how Nor Cal goes from horrible drought to way too much water in a few months. How did these lakes go from historicly low levels to busting at the seams!? There has been a lot of rain but only about 125% or 150% of normal. It's not like it's 500% of normal. I wish I understood this better.
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Old 02-13-2017, 10:30 AM   #19
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Four years ago I chaperoned a 9 day field trip covering CA's water system... Oroville dam was one of the main stops since it feeds into the Sacremento delta, which then feeds the aquaduct system... (So it indirectly stores and provides the bul of the water for the central valley and LA and Orange county.)

We had some back scene tours of the dam and drove right next to the spillways (that portion of the road we drove on now is gone, based on video I saw this morning.) The vibration from the water on the spillway was intense... and this was during the drought!!!!!

The last two years had decent rain/snow fall - not enough to say we're "out of the drought" - but it didn't increase drought conditions... this year Northern California has been hit with storm after storm... And that's why the lake is full. So is Shasta Lake, Mono Lake, and other lakes that were super low during the drought.

I know the salmon hatchery (which we also toured) has been evacuated - including all the roe and baby fish... not an insignificant task.
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Old 02-13-2017, 10:55 AM   #20
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Quote:
Originally Posted by jdmorton View Post
It's been quite a while since I had to study rudimentary dam and spillway design in college; however, I would guess cavitation was involved. Cavitation is the bane of spillway design. It is a well known phenomenon in water hydraulics and is extremely powerful force that can erode concrete under the proper conditions.

Here's a short description of cavitation from a U.S. Department of Interior and U.S. Army Corps of Engineers chapter from their dam safety book on spillway cavitation:

"Cavitation is the formation of vapor cavities in a liquid. Cavitation occurs in high velocity flow, where the water pressure is reduced locally because of an irregularity in the flow surface. As the vapor cavities move into a zone of higher pressure, they collapse, sending out high pressure shock waves. If the cavities collapse near a flow boundary, there will be damage to the material at the boundary. Cracks, offsets and surface roughness can increase the potential for cavitation damage. The extent of cavitation damage will be a function of the cavitation indices at key locations in the spillway chute and the duration of flow."

The following link containing the above explanation will give you more information than you will ever need - or want - to know on spillway cavitation: https://www.usbr.gov/ssle/damsafety/...3-20150610.pdf

This is why I ended up in the 'soft side' of engineering (conducting studies and interpreting regulations) rather than actual design work
Re:cavitation damage and dams, what happened at the Glen Canyon Dam in 1983 with record rainfall and spillway damage is explained in fascinating detail in the book, The Emerald Mile, by Kevin Fedarko. Great read not just for that reason.
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