Oroville Dam Spillway Failure

[deirdre]

why inflows minus primary spillway outflows would not equal outflows over the emergency spillway?

he seems to be saying (i think) because as the inflow flows in, it then spreads out over 16,000 acres. so it takes quite a while for that inflow to actually reach the outflow point so they have to keep changing their math equations to detemine what will hit the outflow point, when.

 

[deirdre]

I agree....I haven't seen one mention of this in my local news, or National TV news coverage

well its not like its a 'disaster'. people arent in danger of losing their lives like with widespread wild fires or anything.

its just a broken dam spillway.

 

[MaryL]

well its not like its a 'disaster'. people arent in danger of losing their lives like with widespread wild fires or anything.

its just a broken dam spillway.

@ Deirdre: I would like to know if the engineers inspecting the damage on the spillway evaluate the type of concrete used to build the dam? Was the concrete designed to withstand such extreme weather? What type of soil did the original construction company use as landfill, and did it compromise the integrity of the concrete poured? The original construction company, and low bidder was Oman Construction Co LLC out of Nashville.

I find the Oroville Dam Spillway crumbling very newsworthy; glad you are covering it.

 

[Marian]

Mick West: Could you address the information presented on this blog? (I live in Oroville.)

https://www.linkedin.com/pulse/oroville-dam-failure-scott-cahill

 

[Leifer]

well its not like its a 'disaster'. people arent in danger of losing their lives like with widespread wild fires or anything.

its just a broken dam spillway.

We in California have had years of drought, so when it seems dams that are suddenly overfilling...is kinda news.
I think Mick's post was saying what you are saying...."There's no danger to the dam".....it's just that we were unprepared for the damn overflow....(lol)

 

[MaryL]

We in California have had years of drought, so when it seems dams that are suddenly overfilling...is kinda news.
I think Mick's post was saying what you are saying...."There's no danger to the dam".....it's just that we were unprepared for the damn overflow....(lol)

@Leifer: I get the drought all-too-well; we live here in Butte County, 14 miles from the Oroville Dam spillway. I was very happy to see that the 'auxiliary' dam was sufficient...but, I have a lot of questions about the integrity of the dam...time will tell. Less than 24 hours ago, the DWR stated that we were probably not going to have to use the 'auxiliary' spillway (that's never been used).

I saw a question about the DWR Acting Director, William Croyle...http://www.dailykos.com/story/2016/...-CA-DWR-officials-are-retiring-at-end-of-year.

 

[Bfahome]

The A block of The Rachel Maddow Show last night was dedicated to covering the spillway failure, not so much in a technical breakdown sort of way but more of a "hey you guys this is happening" sort of way. The block mostly gave some background on the dam's history and some perspective on how physically large the issue is. Special mention to the emphasis that the dam is not in danger of failing and the biggest issue would probably be the massive erosion that the uncontrolled water flow will likely cause.


Source: http://www.msnbc.com/rachel-maddow/watch/oroville-dam-in-crisis-raises-alarm-in-california-874905667526


Was kind of a fun moment for me because when the mention of the dam came up I already knew what the story would be about because of this thread.

 

[Bleodswean]

well its not like its a 'disaster'. people arent in danger of losing their lives like with widespread wild fires or anything.

its just a broken dam spillway.

Yes, but not all news is disaster-focused. The dam is the tallest earthen dam in the nation. California has been under severe drought conditions. Oroville serves much of the water needs for the state. And this is a very expensive failure of the spillway. I don't think the dam is going to fail, nor do I believe that disastrous flooding will result. But I do believe we will see near total failure of the spillway and serious ecological consequences. Not to mention the $$$.

Seems news-worthy. But I may just be feeling terribly frustrated with my local coverage and "Bob made a hole in one in his backyard golf course yesterday" headlines.

 

[Leifer]

We in California have had years of drought, so when it seems dams that are suddenly overfilling...is kinda news.

......and this sort of weather news, unfortunately leads to conspiratorial speculation, among active conspiracy believers.
Look at the comments here....

Source: https://www.youtube.com/watch?v=3hhayGDxMks&t=109s

So it's good to explain it first (preemptive debunk)

 

[Mick West]

n the video from DWR press conference, did you guys understand his answer to the question (at about 27:56 in the video) about why inflows minus primary spillway outflows would not equal outflows over the emergency spillway?

The inflows make the lake level rise, the lake level will rise until the inflows equal the outflows.

 

[Mick West]

Mick West: Could you address the information presented on this blog? (I live in Oroville.)

https://www.linkedin.com/pulse/oroville-dam-failure-scott-cahill

He says "If the flow continues for a long enough time, with sufficient velocity, the reservoir will be voided by the migration of the erosion to the pool (cut-back). I cannot tell if failure is imminent, from Ohio,"

This is all literally true. However he seems to be thinking that the spillway is in the dam. It's not, it's in the mountain Northwest of the dam. Eroding a dam is very different to eroding a mountain. A dam would fail in hours or days. A mountain will last for years - assuming the spillway is well situated.

The Emergency spillway is designed to not fail in an emergency situation of 700,000 cfs. It's only getting about 1% or 2% of that.

 

[MaryL]

The inflows make the lake level rise, the lake level will rise until the inflows equal the outflows.

I understand the inflow data...however, didn't the DWR state that once the 'auxiliary' spillway is used; they cannot measure outflow?

 

[Mick West]

Why doesn't someone send a drone up?

They have. DWR has been using drones with LIDAR to map the area. They have also shot video:

Source: https://www.youtube.com/watch?v=bephol1Ormg

 

[Mick West]

I understand the inflow data...however, didn't the DWR state that once the 'auxiliary' spillway is used; they cannot measure outflow?

They can't measure it in the same way as the main spillway. The Emergency spillway is just a long weir that varies in height and shape along its length, so you can only get rough calculated figures from how high the level of the lake is. There was discusson of the calculation on the previous page.
https://www.metabunk.org/oroville-dam-spillway-failure.t8381/page-2#post-199766

 

[Mick West]

Here is an estimated rating curve for the spillway. It is only an estimate because I do not know if the elevation of the spillway along the parking lot has the same top elevation as the ogee crest spillway. I have used a weir coefficient (C, not to be confused with discharge coefficient Cd) of 3.0 as a compromise between that of an ogee crest (up to 3.8) and the parking lot (broad crest - roughly 2.0). The weir equation is Flow in cfs = C x length x (depth over spillway crest ^ 1.5). Length and depth are in feet. The horizontal scale is the height of the reservoir surface above the spillway crest.

View attachment 24451

Currently 902.22 is nominally 1.22 feet, so from Norm's graph we would estimate around 6000 cfs. This is just a rough estimate though, with a number of variables.

 

[MaryL]

He says "If the flow continues for a long enough time, with sufficient velocity, the reservoir will be voided by the migration of the erosion to the pool (cut-back). I cannot tell if failure is imminent, from Ohio,"

This is all literally true. However he seems to be thinking that the spillway is in the dam. It's not, it's in the mountain Northwest of the dam. Eroding a dam is very different to eroding a mountain. A dam would fail in hours or days. A mountain will last for years - assuming the spillway is well situated.

The Emergency spillway is designed to not fail in an emergency situation of 700,000 cfs. It's only getting about 1% or 2% of that.

According to http://www.petersoncat.com/history/oroville-dam

(you will have to scroll down to see the pics and data about Oroville Dam)

For borrow, Oman used dredge tailings left over from turn-of-the-century gold mining operations, 14 miles away.

By early 1968, the 748-ft high dam wall was complete, making it the highest earth-fill dam in the nation. Eighty million cubic yards of material had been moved, from start to finish, with a total price tag of $439 million.

By May 1968, the 3.5 million acre-foot reservoir was filled and ready for dedication by Governor Ronald Reagan

 

[Leifer]

Armchair physics (in other words I'm guessing).....If you look at the main spillway, there are concrete "dental teeth" at the bottom, just before the overflow enters the river. This is to deflect any strong flow from digging a hole in the river at the spillway mouth....in essence "spraying much of the water" into the river. (rather than pouring or shoving the water into the river('s) bottom, preventing erosion at the spillway bottom.)

Not sure if this is useful here, other than this action is engineered and on purpose.

Here is an older vid, acting as it should....

 

[Mick West]

Posted about an hour ago, but I guess this was around 4PM based on the light.


Source: https://twitter.com/ProComKelly/status/830588936279846912

 

[Marian]

He says "If the flow continues for a long enough time, with sufficient velocity, the reservoir will be voided by the migration of the erosion to the pool (cut-back). I cannot tell if failure is imminent, from Ohio,"

This is all literally true. However he seems to be thinking that the spillway is in the dam. It's not, it's in the mountain Northwest of the dam. Eroding a dam is very different to eroding a mountain. A dam would fail in hours or days. A mountain will last for years - assuming the spillway is well situated.

The Emergency spillway is designed to not fail in an emergency situation of 700,000 cfs. It's only getting about 1% or 2% of that.

Here are more of his remarks regarding that:
"14 minutes ago: water has begun to flow in the emergency spillway of the Oroville Dam. This will increase scour, but in the right abutment. There appears to be high recovery rock beneath the abutments, so now it becomes an issue with topography and hydraulics. If the erosion of the emergency spillway can stay linear and within the em. spillway, the dam, though damaged will survive. This is a dam operating as it was designed to do. If, however the erosion occurs toward the left (looking downstream) and if it communicates with the eroded scour of the principal spillway, depending on duration, the right groin of the dam could be compromised. If this event occurred, it would result in a V notch failure of the earthen dam at the right groin. Let us all hope that it stays linear and that the sun comes out."

Can you help me interpret that?
thank you so much.

 

[Mick West]

Here are more of his remarks regarding that:
"14 minutes ago: water has begun to flow in the emergency spillway of the Oroville Dam. This will increase scour, but in the right abutment. There appears to be high recovery rock beneath the abutments, so now it becomes an issue with topography and hydraulics. If the erosion of the emergency spillway can stay linear and within the em. spillway, the dam, though damaged will survive. This is a dam operating as it was designed to do. If, however the erosion occurs toward the left (looking downstream) and if it communicates with the eroded scour of the principal spillway, depending on duration, the right groin of the dam could be compromised. If this event occurred, it would result in a V notch failure of the earthen dam at the right groin. Let us all hope that it stays linear and that the sun comes out."

Can you help me interpret that?
thank you so much.

He's basically saying that if the erosion goes all the way around the hill to the dam, then the dam will fail. This does not seem likely based on the topology of the hill and current erosion patterns.

 

[Mick West]

Some later photos, sun going down, maybe 5ish?

Source: https://twitter.com/KRCR7/status/830607408523141121


Merged:

 

[Mick West]

Bottom of the emergency Spillway

 

[Mick West]

More pics here: http://pixel-ca-dwr.photoshelter.co...yfg/G00003YCcmDTx48Y/Oroville-Spillway-Damage

 

[Carl Leoanrd]

A big thank you for the information and the images. It's not well covered in the "normal" media. I was hoping for some helicopter shots on the evening KCRA news, but no such luck.

It appears that CDEC is not setup to deal with flows over the emergency spillway as the outflow numbers have stayed constant at 55k even though we know that a decent amount is going over the emergency spillway since the lake is 2 feet over the spillway.

I'm guessing that the inflow numbers are being reduced by the emergency spillway amount.

CDEC also shows that the release was scheduled to go back to 65k cfs at 4 pm today, but either that didn't happen or it's not registering right.

 

[Mick West]

Here are more of his remarks regarding that:
"14 minutes ago: water has begun to flow in the emergency spillway of the Oroville Dam. This will increase scour, but in the right abutment. There appears to be high recovery rock beneath the abutments, so now it becomes an issue with topography and hydraulics. If the erosion of the emergency spillway can stay linear and within the em. spillway, the dam, though damaged will survive. This is a dam operating as it was designed to do. If, however the erosion occurs toward the left (looking downstream) and if it communicates with the eroded scour of the principal spillway, depending on duration, the right groin of the dam could be compromised. If this event occurred, it would result in a V notch failure of the earthen dam at the right groin. Let us all hope that it stays linear and that the sun comes out."

Can you help me interpret that?
thank you so much.

An important point regarding this is that the main spillway runoff is now running clear. This means that it's no longer eroding anything. There's really no reason why the lower portion would proceed towards the dam. It seems fairly likely the main spillway is essentially stable (in the short term) at this flow rate.

Compare with the red/brown water from the emergency spillway, just starting to cut into the hill. Since it's to the north it's no danger to the dam itself.

 

[Mick West]

So they now have three days of sun. The overflow will probably end tomorrow with some essentially cosmetic damage to the hillside. The hope would be that they can continue 55K cfs down the main chute and make room for next week's rains. Right now it's looking a bit damp, 2.2 inches over six days at Berry Creek (near the middle of the watershed). It's going to be a race to try to get through wednesday and thursday, which (current forecast) have the worst of the rain. Note though that this is less intense rain than before, where we were getting several days in a row of >1", and some >2".

https://www.wunderground.com/q/zmw:95916.1.99999

 

[Carl Leoanrd]

In today's news conference there was a discussion of a modification to the main spillway. No details were given, but it was stated that they wanted to make a change to better stabilize against headward erosion. The goal is to run the lake down enough that they could stop the flow for a day (or more) to do that work.

This next storm is also colder. A big part of the current overflow is that the last rain was warm and melted a lot of existing snow.

 

[Mick West]

Very interesting lawsuit from 2005 arguing for the need for the emergency (auxiliary) spillway to have a lined chute:
https://elibrary.ferc.gov/idmws/common/downloadOpen.asp?downloadfile=20051017-5033(13724888).pdf&folder=19973004&fileid=10849040&trial=1

Oroville Dam includes two spillway facilities, the main spillway (controlled by gates) and an ungated "overpour" spillway, consisting of a 1,730 ft long spillway lip (ogee crest) at elevation 901 feet, with no spillway below. Maximum surcharge operations envision 16 feet of water depth over the ungated spillway, plus additional freeboard space.
...
The discharge area below the emergency spillway is not armored and extensive erosion would take place if the emergency spillway were used. The spillway road and possibly high voltage transmission towers would be impacted. (p. II-1) Because the area downstream from the emergency spillway crest is an unlined hillside, significant erosion of the hillside would occur. (p. II-5) "The hillside between the emergency spillway and the Feather River would be subject to severe erosion when water flows over the spillway. Depending on the rate of flow, the erodable area . . . could range from 50 to 70 acres. The amount of soil, rock, and debris that would fall into the Feather River could be very large, depending on the depth of erosion. There could be damages to downstream structures, including the Thermalito Diversion Dam and Powerplant, Fish Barrier Dam, and highway bridges. If there is river channel blockage below the spillway, there could be impacts on operation of Hyatt Powerplant

Lots of interesting detail in the file.

 

[Mick West]

In today's news conference there was a discussion of a modification to the main spillway. No details were given, but it was stated that they wanted to make a change to better stabilize against headward erosion.

I suspect they will try to do something like they did at the foot of the emergency spillway - basically a bunch of big rocks cemented together - and try to tie it to the upstream concrete. It will be interesting engineering.

 

[Mick West]

The problem is they have very little idea of what the situation is until they cut off the water, then they have to come up with a plan and act fast.

 

[Graham2001]

Very interesting lawsuit from 2005 arguing for the need for the emergency (auxiliary) spillway to have a lined chute:

I will be having a look at that report once I have it down. When I was looking at the pictures of the emergency spillway, one of the first things I thought of was to wonder why when the road was put through they didn't design it with culverts so that the water would pass under the road surface without affecting it. As it stands they will stand a very high chance to loose that road.

Also looking at the current set of videos that appeared in the last 24 hrs I found this piece of scaremongering by a user called Jason Robley:

We are up shit creek. The tallest in the nation, at 770 ft it holds back 59,344,000m3 of water over an area of 3,537,577 acre-ft ! I live in Northern Ca and I'm renting a fucken boat! And I'm 75 miles away! But it's all down hill and it's ready to give way. Here is the link for the 24HR webcam at the dam.

Source: https://www.youtube.com/watch?v=4FqEtY2ktzg


There are also a pair of channels (oldmarinevaughn & King Truth LoganLLc) which seem to be hosting the same videos with titles like "Oroville Dam UPDATE LEAVE THIS AREA NOW" & "IT HAS STARTED! Oroville DAM EMERGENCY DAM REAL" along with several obviously Christian channels offering scare-mongering interpretations of events.

Lastly here is the latest aerial footage of the effects of the overflow. Lots of scare-mongering comments of this kind:

I operated a 100 foot high dam holding back about a billion gallons in Ohio for 7 years. Anyone find it strange that the outflow from the power plant is muddy? That water should be clear as a bell (the water that comes out from under the dam, not from the busted up spillway). THAT IS NOT A GOOD SIGN! If we saw muddy outflow comin from under our dam the state would have shut us down RIGHT NOW. Unfortunately, the first thing they would order us to do is DRAIN THE LAKE which oroville doesn't have the luxury of doing without causing more problems. Believe me, they aint tellin half the true story here.

Source: https://www.youtube.com/watch?v=bCK1FSKfPwU

 

[Mick West]

Content from external source This [power] plant cannot operate without being connected to the grid.
Why not, exactly?

It needs power to open the valves.

 

[Carl Leoanrd]

12:23 in the above video:

This [power] plant cannot operate without being connected to the grid.

Why not, exactly?

It's my understanding that there can be several different mechanisms in addition to the need for external power to operate valves before the generators are making any power. In normal operation the energy in the water is extracted by the turbine and turned into electricity. Without that load the water flow changes, this can lead to cavitation which damages the turbine. There is also a control system to regulate the speed of the turbine. It might not be able to deal with no load condition.

A lot of large hydro plants have this same limitation.

Basically, it's just not built for it.

 

[Mick West]

Lastly here is the latest aerial footage of the effects of the overflow. Lots of scare-mongering comments of this kind:

Content from external source I operated a 100 foot high dam holding back about a billion gallons in Ohio for 7 years. Anyone find it strange that the outflow from the power plant is muddy? That water should be clear as a bell (the water that comes out from under the dam, not from the busted up spillway). THAT IS NOT A GOOD SIGN! If we saw muddy outflow comin from under our dam the state would have shut us down RIGHT NOW. Unfortunately, the first thing they would order us to do is DRAIN THE LAKE which oroville doesn't have the luxury of doing without causing more problems. Believe me, they aint tellin half the true story here.

The dam isn't putting out any water at all from the base (the power station and some fish stuff). They shut it off because the spillway usage raised the basin level too much. That's all spillway runoff water.

 

[Z.W. Wolf]

Why not have a diesel backup generator? This is starting to sound a little Fukushima...

 

[Z.W. Wolf]

It's my understanding that there can be several different mechanisms in addition to the need for external power to operate valves before the generators are making any power. In normal operation the energy in the water is extracted by the turbine and turned into electricity. Without that load the water flow changes, this can lead to cavitation which damages the turbine. There is also a control system to regulate the speed of the turbine. It might not be able to deal with no load condition.

A lot of large hydro plants have this same limitation.

Basically, it's just not built for it.

So the water can only follow one path... through the turbines; and if the generators aren't producing electricity, and removing kinetic energy from the water, the water moves too fast and causes erosion from cavitation. Is that right?

 

[Bleodswean]

We have national. AP and The Weather Channel.

http://www.msn.com/en-us/news/video...emergency-spillway/vi-AAmQ57q?ocid=spartanntp

"This is a big deal, guys."

 

[Mick West]

We have national. AP and The Weather Channel.

http://www.msn.com/en-us/news/video...emergency-spillway/vi-AAmQ57q?ocid=spartanntp

"This is a big deal, guys."

Yeah, and the fearmongers and clickbaiters are coming out the woodwork. People just making up (or repeating) things that are entirely wrong. For example:

Source: https://twitter.com/jackeegan/status/830803298827587584


Obviously someone made up that figure as it's actually 902.5' and dropping. Charitable they might be confusing it with the worst case scenario of what would happen if we had a 30" storm right now. But people are unfortunately spreading stories about how the dam is going to collapse. In fact it seems like things have pretty much stabilized now.

Have a look at this from yesterday.

There will be new images this morning, but the lake level is decreasing, and the emergency spillway damage seems like it's just going to be lots of soil runoff and some easily rebuilt roads.

Focus should move back to the main spillway, and if that can last through the coming storms.

 

[Mick West]

More on why the generators are shut off

http://www.krcrtv.com/news/breaking-news/dwr-holds-press-conference-about-oroville-dam/327843952

A new area of focus in the DWR press conference was that of the hydroelectric power plant that sits at the base of the dam. The plant, which can allow for a small amount of water to be released through the dam, is currently shut down. In its current state, no water would pass through putting more pressure on the spillway system.

While operating, the plant can push through 14,000 cfs of water which would help with reservoir management. The power generation was halted when water levels in the channel rose too high and comrpomised operation.

According to Croyle, the plant faces two challenges. First, if debris washes upstream and gets into the plant it could damage equipment and cause them to shut down operations. Second, if the power lines that connect the plant to the grid go offline then the plant is no longer able to operate, or even let water through. Currently, the power lines are stretched across the area where the emergency spillway is releasing water, and erosion could damage the power poles.

PG&E had been doing preparatory work on the lines in the past couple of days, but with water coming off the emergency spillway it became no longer safe for them to continue their work and they had to back off. A spokesman for PG&E said that they are working closely with the DWR to monitor this issue.

I imagine they will turn it back on today or tomorrow when they turn off the main spillway for inspection and interesting repairs.

 

[RedNeckGeek]

I don't have much to contribute to the discussion, but I did want to express my appreciation to Mick for hosting this site and starting the thread, and to all the posters for keeping the discussions fact based and not engaging in a lot of hysterics. I live above the dam and my back yard abuts Lake Oroville, so what goes on at the dam is of great importance to me.

As a retired engineer my heart goes out to the people working to reason their way toward a solution. They are dealing with 40+ year old infrastructure and most of the people that designed and built it are no longer available to lend their experience and guidance to the effort. They're also up against Mother Nature and have no control over the path she takes. If these challenges weren't enough, the attitudes held by much of the press and the public are especially unfriendly to technology, especially that which impacts the environment. The biggest contribution this forum can make is to facilitate the dissemination of factual information related to the spillway failure to counter the fear mongering that's already going on and the witch hunts that will surely follow.

Thank you!