Oroville Dam

[Tobra]

Rain in Sacramento today, skies look pretty ominous to the North and East, which is where Butte County is. Supposed to get a 1/2 inch tomorrow, with more to come on the weekend.

[sammyg2]

Originally Posted by Por_sha911

https://thinkprogress.org/how-much-of-californias-drought-was-caused-by-climate-change-scientists-now-have-the-answer-56ae9e33555f#.9058lb4rn

I wonder how much that bull **** cost the the taxpayers.

[daepp]

Terrific engineering blog where geeks are striving for an accurate discussion:

https://www.metabunk.org/oroville-dam-spillway-failure.t8381/

[Seahawk]

Originally Posted by daepp

Terrific engineering blog where geeks are striving for an accurate discussion:

https://www.metabunk.org/oroville-dam-spillway-failure.t8381/

That link is the best. Thanks!

[DonDavis]

Originally Posted by Seahawk

That link is the best. Thanks!

Agreed. The geek is strong over there. A Ham radio guy was chatting about wavelength stuff and resonance. Too cool.

Just wish the mass media would take a cue from there as well.

But alas, Chicken Little garners more attention.

[red-beard]

Originally Posted by DonDavis

Agreed. The geek is strong over there. A Ham radio guy was chatting about wavelength stuff and resonance.

He wrong but he is in the right direction. I expect the scouring is due to the velocity point where cavitation starts to occur. When water increases in velocity, the static pressure in that area is reduced. If it moves fast enough, the pressure drops to the point the water boils, making a bubble. The bubble blocks water, which slows it down, increasing pressure and the bubble collapses. Water then hammers the spot where the bubble was.

We run into the opposite of this in high pressure gas releases. The "layered" look is actually real. At each boundary is actually a sonic pressure drop. If the pressure is high enough, you get multiple mini sonic booms, shockwaves. It is one of the reasons "jet" engines are very loud. The newer designs, high bypass turbofans, you push lots of fast air, but the thrust is not above the speed of sound.

[Rinty]

Originally Posted by daepp

Terrific engineering blog where geeks are striving for an accurate discussion:

https://www.metabunk.org/oroville-dam-spillway-failure.t8381/

Great site; thanks for linking.

[jyl]

Can someone summarize the situation?

Is the lake level low enough that the current storm will not require the emergency spillway to be used?

Is the regular spillway being further damaged, enough to potentially restrict its usage?

Has the emergency spillway been reinforced enough to be safely used?

[Tobra]

Let me give it a shot John.

They lowered the lake level significantly during a break in the weather. Lowered enough, maybe, depends on how much it rains.

If you look at the dam, the spill ways are off to the left of the cement part that you see and think, that's a dam. The cement part is anchored to bedrock on both sides. The water from the hydro electric plant comes out on the right of the dam and flows out below it. Max flow for it is like 15% of the main spill way. The first spillway you see to the left of the dam is the main one, it can be dialed up or down, even off, I believe max is 150,000 cfm. There are drains under the spillway that are supposed to take water out from under the spillway in such a manner that the dirt under it does not wash out; supposed to, I say. If the flow goes much over 200,000, it overwhelms the levees and there is flooding downstream.

They worked round the clock for a few days on repairs to the spillways. Supposed to rain today, rain hard tomorrow. The emergency spill way is like a little dam, off to the left side of the main one, top of which is 30' lower than the main dam. No gates on it though, so if it gets that high, it goes over the top and down that spillway. This is the part that is in danger of failing. The way it is laid out, if it goes, the reservoir behind the dam drops 30' with alacrity, and bad things will ensue. Bedrock separates the dam from the part that could potentially wash out, so it is probably not going anyplace.

Kids are at Lake Tahoe. I will talk to them today, will be interested in how the drive up there was, and how hard it is snowing. If it is raining at the lake level, it might not work out so well. A lot of the watershed for that dam is above 5000' with snow on the ground already. If it is raining up there, it will melt enough snow to make it get ugly in a hurry.

[daepp]

A great op-ed in the LA Times by Victor Davis Hanson, 6th generation Californium, grape farmer and professor of the classics:

"The crisis at Oroville is a third act in the state’s history: One majestic generation built great dams, a second enjoyed them while they aged, and a third fiddles as they now erode."

The Oroville Dam disaster is yet another example of California's decline - LA Times

[jyl]

Originally Posted by Tobra

Let me give it a shot John.

They lowered the lake level significantly during a break in the weather. Lowered enough, maybe, depends on how much it rains.

If you look at the dam, the spill ways are off to the left of the cement part that you see and think, that's a dam. The cement part is anchored to bedrock on both sides. The water from the hydro electric plant comes out on the right of the dam and flows out below it. Max flow for it is like 15% of the main spill way. The first spillway you see to the left of the dam is the main one, it can be dialed up or down, even off, I believe max is 150,000 cfm. There are drains under the spillway that are supposed to take water out from under the spillway in such a manner that the dirt under it does not wash out; supposed to, I say. If the flow goes much over 200,000, it overwhelms the levees and there is flooding downstream.

They worked round the clock for a few days on repairs to the spillways. Supposed to rain today, rain hard tomorrow. The emergency spill way is like a little dam, off to the left side of the main one, top of which is 30' lower than the main dam. No gates on it though, so if it gets that high, it goes over the top and down that spillway. This is the part that is in danger of failing. The way it is laid out, if it goes, the reservoir behind the dam drops 30' with alacrity, and bad things will ensue. Bedrock separates the dam from the part that could potentially wash out, so it is probably not going anyplace.

Kids are at Lake Tahoe. I will talk to them today, will be interested in how the drive up there was, and how hard it is snowing. If it is raining at the lake level, it might not work out so well. A lot of the watershed for that dam is above 5000' with snow on the ground already. If it is raining up there, it will melt enough snow to make it get ugly in a hurry.

Thanks.

I am curious how the main spillway has not been further damaged by the days of 100K c.f.m. flow. Seems like it was rapidly damaged by the flow in a few days before about 2/14, and then the damage suddenly stopped progressing despite continuing flow. Which seems odd.

[trekkor]

I'm very concerned about the Oroville dam breaking.

The Teton dam for reference:

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

[ossiblue]

Originally Posted by trekkor

I'm very concerned about the Oroville dam breaking.

The Teton dam for reference:

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

Concern is always warranted, but to compare the failure of the Teton Dam with the possible failure of Oroville is not warranted. Teton failed during initial filling as a result, it was later determined, of flaws/fissures in the underlying bedrock and designs inadequate to address those flaws. Oroville has been in operation for over 50 years, many times at full capacity. The integrity of the dam itself has never been an issue, to date. The current problems relate to the spillways, not the dam face. Failures of the spillways would lead to a potential catastrophic event in and of itself, but not to a failure of the dam.

[widebody911]

Originally Posted by daepp

A great op-ed in the LA Times by Victor Davis Hanson, 6th generation Californium, grape farmer and professor of the classics:

"The crisis at Oroville is a third act in the state’s history: One majestic generation built great dams, a second enjoyed them while they aged, and a third fiddles as they now erode."

The Oroville Dam disaster is yet another example of California's decline - LA Times

Screw the dam! I want to be able to get from Fresno to Bakersfield in 1 hour!

[Danimal16]

Originally Posted by daepp

A great op-ed in the LA Times by Victor Davis Hanson, 6th generation Californium, grape farmer and professor of the classics:

"The crisis at Oroville is a third act in the state’s history: One majestic generation built great dams, a second enjoyed them while they aged, and a third fiddles as they now erode."

The Oroville Dam disaster is yet another example of California's decline - LA Times

Having spent my civilian engineering career in wet utilities, this LA Times article is worth the read.

Over the course of 30 years doing this stuff, the one hot button term that we should vehemently despise is "deferred maintenance". The above article also discusses the role of false narratives and failure to complete the facilities as originally sized. It is down right depressing.

Maintenance of existing facilities is not glamorous. Politicians and other power brokers hide maintenance in order to draw attention and fund their pet projects; projects that are "shiny and new". These reprobates also know that when the degradation of facilities can no longer be ignored; they will be ten to twenty years long gone.

Leaders and other civic minded men and women understand the importance of maintenance and repair of infrastructure.

So the next time some politician utters the words "deferred maintenance" shoot em.

[Danimal16]

Originally Posted by trekkor

I'm very concerned about the Oroville dam breaking.

The Teton dam for reference:

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

Apples and oranges, poor comparison to Oroville situation.

However, it has similarities to the Saint Francis Dam failure.

https://www.kcet.org/history-society/the-flood-st-francis-dam-disaster-william-mulholland-and-the-casualties-of-la

[ossiblue]

Originally Posted by Danimal16

Having spent my civilian engineering career in wet utilities, this LA Times article is worth the read.

Over the course of 30 years doing this stuff, the one hot button term that we should vehemently despise is "deferred maintenance". The above article also discusses the role of false narratives and failure to complete the facilities as originally sized. It is down right depressing.

Maintenance of existing facilities is not glamorous. Politicians and other power brokers hide maintenance in order to draw attention and fund their pet projects; projects that are "shiny and new". These reprobates also know that when the degradation of facilities can no longer be ignored; they will be ten to twenty years long gone.

Leaders and other civic minded men and women understand the importance of maintenance and repair of infrastructure.

So the next time some politician utters the words "deferred maintenance" shoot em.

+1

I will only add that "deferred maintenance " also appears when balancing a budget--an accounting move to keep things solvent until the degraded facility becomes a crisis and, typically, someone else's problem.

[Tobra]

I think the spillway was compromised by soil washing out under it, and was further damaged when the gates were wide open to take pressure off the emergency spillway. A bunch of debris ended up at the bottom of the spillway, and you can really appreciate the change in the bay if you look at some aerial photos.

SF Bay last April compared to now.

[rusnak]

^Oh. My. God.

[jyl]

Originally Posted by rusnak

^Oh. My. God.

Isn't it a good thing, for the Delta and Bay to get all that sediment and fresh water?