Oroville Dam in danger of failing

[Ronstar]

I've surveyed several dams and spillways for renovations, none of which were damaged to the extent of the Oroville spillway. I remember the engineers saying that it's best to have a wide spillway.

 

[MichaelB]

I don't know how accurate this article is, but if it is accurate, the scenario outlined is this article is frightening:

Governor Brown: Evacuate Sacremento or One Million Could Die From Oroville Dam – Dave Hodges – The Common Sense Show

The absence of any expert opinions, the reference to a talk show host, and the extreme nature of the political talk gives a clue - not accurate at all is my non-expert opinion.

Sacramento is almost 70 miles from Oroville. The water would have to travel that entire distance without running off and then drown everyone in the city of Sacramento and the greater metropolitan area.

 

[Mango1956]

Just recently finished a book called "The Emerald Mile". It's the story of Kenton Grua (with 2 others) who set the speed record for rowing through the Grand Canyon. 37 hours! They made the run during historic flooding in 1983, which followed Lake Powell "filling up" and the dam controllers being forced to release lots of water!

There were serious problems in one of the spillways, first time it was ever used. Sounds similar, basically tore it up. The post mortem came to the conclusion that it was a manufacturing defect, a blemish on the concrete surface, which resulted in cavitation, that got it started. Once the damage started, it's a positive feedback loop, just keeps getting worse. When they repaired it, they made changes to allow for "a cushion of air" to be in the flow to avoid cavitation. Not sure how that worked, just the description.

The book covers much more than just the speed run, lots of history. I enjoyed it, though it was a slow read.

More info:
https://en.wikipedia.org/wiki/Risks_to_the_Glen_Canyon_Dam

Go down to 1983 flood and 1984 repair.

Glad you enjoyed the book as well! It's in my top 10! I think if you have done a fair amount of whitewater rafting (we have done some, but never down the GC) the sections describing the run those guys did mean more to you than if you haven't experienced the hydraulics of whitewater. Engineers and western history buffs will love this book!

 

[Gumby]

"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."

As a side note, cavitation is a problem in other areas too. For example, under certain depth and speed conditions, the screw (propeller) of a submarine will cavitate. When the bubbles collapse, they make noise. And that is one of the ways we submariners find our adversaries - we listen for the cavitation noise.

 

[oldphd]

Glad you enjoyed the book as well! It's in my top 10! I think if you have done a fair amount of whitewater rafting (we have done some, but never down the GC) the sections describing the run those guys did mean more to you than if you haven't experienced the hydraulics of whitewater. Engineers and western history buffs will love this book!

I've done a moderate amount of WW rafting, including a 15 day trip down the GC on an oar/paddle trip. Took my 16 year old son, it was a fantastic trip! A highlight among 4 continents, 25-30 countries, 20ish major caribbean islands, and all 50 states. So I have a fair amount to compare it to.

My trip was about 15 years ago, and I was pleased that I could recall many of the rapids as he called them out by name, though the huge water levels I'm sure made them look totally different. Simply unbelievable that these guys did that trip! They were crazy/brave/whatever, but definitely marched to a different drummer.

 

[Another Reader]

Here's an interesting take on the potential for disastrous flooding from a former Army Corps of Engineers engineer who sits on the Central Valley Flood Protection Board.

Expert says Highway 70 corridor 'gone' if emergency spillway collapses | The Sacramento Bee

 

[Just_Steve]

As a side note, cavitation is a problem in other areas too. For example, under certain depth and speed conditions, the screw (propeller) of a submarine will cavitate. When the bubbles collapse, they make noise. And that is one of the ways we submariners find our adversaries - we listen for the cavitation noise.

And cavitation will destroy a Diesel engine when the cavitation takes place between the steel piston liners and the cast iron block. Poor maintenance, pretty common problem.

 

[Persn]

For those interested, the sacramento bee at Breaking News, Sports, Weather & More | Sacbee.com & The Sacramento Bee has a number of stories about the effects of a possible collapse of the emergency spillway.

 

[JoeWras]

I wonder how much design is put into these "emergency" spillways?

I know in our recent tropical storm event, a local town's park lake spillway came into action. It was designed to go over the parking lot. Impressive footage. They only had some minor scouring. But then again, we're talking about a lake less than 1% the size of Oroville.

Seems like most of the big lakes here have not have emergency spillway overflow. They always turn up the main spillway before overtopping. But who knows, their time may come when we get back to back hurricanes. Based on this, I'm going to be concerned when that happens.

 

[Ronstar]

I wonder how much design is put into these "emergency" spillways?
....

From what I've seen, "emergency" spillways are not designed to the degree that primary spillways are designed. Most primary spillways are equipped with gates that regulate flow. So the design of the primary spillway usually includes gate design as well. Materials design would include concrete/ rebar, as well as capacity of the subgrade material. Detailed hydraulic calculations would also be performed so that the spillway can carry necessary flow while keeping upstream lake levels at specified flood levels.

On projects that I worked on, "emergency" spillways were generally an overflow structure where water topped the levee in an extreme event. There are generally no gates on "emergency spillways", so the design is less complicated. There probably is some material design to make sure that the spillway material is compacted, etc in order handle the lake pressure and minimize erosion. The hydraulic calculations may indicate where flows from the primary spillway peak and emergency spillway flows begin.

This is a unique case where they are trying minimize the increasing erosion/damage to a collapsed primary concrete spillway while simultaneously minimizing flows/ erosion to a emergency spillway. I'm not sure that design takes this scenario into consideration.

 

[jazz4cash]

The absence of any expert opinions, the reference to a talk show host, and the extreme nature of the political talk gives a clue - not accurate at all is my non-expert opinion.

Sacramento is almost 70 miles from Oroville. The water would have to travel that entire distance without running off and then drown everyone in the city of Sacramento and the greater metropolitan area.

When a websites primary ads are precious metals and emergency food storage systems it makes me wonder.

 

[JoeWras]

This is a unique case where they are trying minimize the increasing erosion/damage to a collapsed primary concrete spillway while simultaneously minimizing flows/ erosion to a emergency spillway. I'm not sure that design takes this scenario into consideration.

Many extreme technology failures are due to multiple failures. This is a good example.

The latest pictures from the main spillway show the new "canyon" being scoured next to and parallel to the bottom of the tailrace. I guess as long as the undermining doesn't work its way up the main spillway anymore, things might work out, assuming no major inflows that the main spillway can't handle.

But, oh boy, there are some major repairs coming. Wow.

 

[Ronstar]

Many extreme technology failures are due to multiple failures. This is a good example.

The latest pictures from the main spillway show the new "canyon" being scoured next to and parallel to the bottom of the tailrace. I guess as long as the undermining doesn't work its way up the main spillway anymore, things might work out, assuming no major inflows that the main spillway can't handle.

I agree.

But, oh boy, there are some major repairs coming. Wow.

I know- I read that they are going to drop rip-rap by helicopter into the primary spillway to mitigate damage in the short term. Then this material would have to be removed when they fix the concrete. I also read that they were going to grout the embankment. I've seen this done once - they shoot material into the ground to stabilize and waterproof the subgrade. Quite an undertaking on a project of this magnitude.

 

[ocean view]

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.

All of the big reservoirs in CA collect snow melt from the Sierras, which typically doesn't start until the spring. This year I think we've had cold storm, then warm storm, then cold storm patterns. Last week's storm was warm with rain at the high elevations. Run-off was greater due to melting snow at the those elevations as well as just the buckets of rain that have been coming down. If the snow had melted in the spring there would be plenty of time to better regulate the lake level.

 

[H2ODude]

No one wants to pay for what the max possible thing Mother Nature can throw at you. I mean, who was the bright light that figured the levees in New Orleans only needed to face a Category 3? Drought planning is even worse, most water supplies are built around a 50 year occurence, or rather a 2% of failure in any year.

The last dam replacement project I worked on had an "emergency spillway" that was basically a cleared area through the woods, designed in 1968. When planning the replacement for the rotting concrete dam and spillway (alkali silica reactivity deterioration of the concrete, it was all....crumbly!) the borings in the emergency spillway showed it would erode like...well....the dirt that it was. According to modern standards it was blocked off so that the max possible precipitation for 24 hours could pass the new dam/spillway...the earthen portion had to be armored with articulated blocks tied together with cables. In NC the max possible pricip for 24 hours IIRC was 28 inches! I know, sounds like some government over reach in setting standards. But, in fact, there have been cases where the same events occurred elsewhere with similar conditions. Don't ask me for sources, I have deliberately flushed all details of my career from my brain.

 

[Rosie]

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.

This:

All of the big reservoirs in CA collect snow melt from the Sierras, which typically doesn't start until the spring. This year I think we've had cold storm, then warm storm, then cold storm patterns. Last week's storm was warm with rain at the high elevations. Run-off was greater due to melting snow at the those elevations as well as just the buckets of rain that have been coming down. If the snow had melted in the spring there would be plenty of time to better regulate the lake level.

 

[Brat]

My Dad was an engineer with the COE in the NW back in the day. I remember the VanPort Flood in the mid-40s. He once warned me not to buy land in New Orleans because of siltation in the Delta, and the dikes along the Mississippi were problematic.

What most people do not know is that dams have a life span. When water permeates the concrete it will cause the steel to oxidize, that process causes the steel to expand and disintegrate the concrete. Over time silt builds up behind a dam which reduces storage capacity and puts pressure on the dam structure. The 'emergency overflow' was something that no one expected to be used so I doubt that its design and construction were scrutinized.

With all the rain/snow N. CA has received in the last 60-90 days the last thing they need is a wet warm storm.

 

[Just_Steve]

Heard a news story today that the money to repair the spillway was appropriated but the work was deferred and the money was allocated to other projects. Great managerial decision.

 

[samclem]

I read that they are going to drop rip-rap by helicopter into the primary spillway to mitigate damage in the short term.

That's gonna be some expensive work. Probably 10 dollars worth of stones delivered with a $500 helicopter ride for the last mile of the trip. But, it's gotta be done, and if it prevents another evacuation, loss of life, or even more $$ for remediation/repair of the main spillway, it is worth it.

I guess the thing to appreciate is how rare this is. We're surrounded by roads, bridges, pipelines, immense multistory structures, the whole electric power grid, etc--and rarely do our efforts let us down in a spectacular way.

 

[Rosie]

How did these lakes go from historicly low levels to busting at the seams!?

This article might help:

https://www.theguardian.com/us-news/2017/feb/14/oroville-dam-flooding-california-drought-weather

After years of drought, northern California has been inundated with more than twice as much precipitation as normal since 1 October. The precipitation is also coming in an inconvenient and unseasonal format: rain.

Typically, a significant amount of a winter season’s precipitation stays frozen in snowpack until spring. But this year, much of that precipitation has been rain, and even when snow has fallen, it has been melted soon thereafter by warm rains.

“It’s a double whammy,” Carlson said.

Lake Oroville typically reaches its highest level in June, after the snow melts. To reach such a peak in mid-February is “extraordinary”, Carlson said. More rain is expected later this week.

 

[imoldernu]

Curious...
How will the rains affect the water table, and the agriculture of California? Short term, long term?

 

[mystang52]

I just commented on how great the light-hearted thread was, about directions and GPS. This is a great thread on a much more serious issue. I wanted to quote a few previous comments, but instead I'll just echo them. I too can't understand how an emergency design can't handle an emergency.
I am NOT being political here, but is there really any surprise that a state government took money from a fund to maintain a dam, and spent it on other purposes? We see this all the time in every state and Uncle Sam.
Finally, I am not an engineer but it seems to me this dam design and the seemingly cavalier approach to maintenance, emergency, etc is a not uncommon example of engineering hubris. Besides Tacoma Narrows, how about the Challenger tragedy, that Minnesota interstate highway bridge collapse, Flint water, etc ? It seems to me too often necessary actions are ignored for purposes of expediency, politics, finances etc.
I hope they can fix this, both temporarily and then long term, without any tragic consequences to life or property.

 

[JoeWras]

This article might help:

https://www.theguardian.com/us-news/2017/feb/14/oroville-dam-flooding-california-drought-weather


After years of drought, northern California has been inundated with more than twice as much precipitation as normal since 1 October. The precipitation is also coming in an inconvenient and unseasonal format: rain.

With all due respect to The Guardian and many other commentators, using the term "normal" is what is confusing things. For California, and most mid-latitude climates, "normal" is a large swing year to year that pivots around the mean, or average. Yes, in some years the average is hit spot on, but that's actually not a normal occurrence.

I know I'm parsing words, but I think this is where the confusion comes as to "how can this happen?" The simple fact of the matter is that when we plan our long term lives: cities, parks, roads, infrastructure, etc., we have to be ready for events far away from the mean. Because, they are normal occurrences.

The sad fact is that for this not-unprecedented high-precipitation event, the dam design was a failure. The main spillway could not handle outflows well within range. The emergency spillway basically couldn't handle anything. They designed that emergency spillway on a wish, a wish it would never get used. That's almost criminal. To see the way the earthen substrate was caving backwards towards the spillway structure astounds me. It looks like it was built on compacted earth. I'd say some swear words here, but I better stop.

The good news is they put caution to the wind on the main spillway and just let it do its thing as the tailrace deteriorates. At least that deterioration seems to be staying far away from the main control structure. Hopefully, the main spillway can handle the expected inflow of the next rain event.

 

[KB]

I live about 75 miles southwest from Oroville and have a home weather station. I keep track the rain I get and have a for a few years. Here is the total rain I received at my house this year compared to a few previous years. I keep track from Jan 1 to Dec 31.

2017 17.93 in the first 42 days
2016 total 30.14
2015 total 13.45
2014 total 14.71

Obviously the last two years have been much wetter than the two previous years. Hopefully the aquifer is beginning to replenish with the additional water we are receiving. Some areas in Southern CA reported that the ground level dropped ten feet or more as the water table dropped.

 

[Another Reader]

With all due respect to The Guardian and many other commentators, using the term "normal" is what is confusing things. For California, and most mid-latitude climates, "normal" is a large swing year to year that pivots around the mean, or average. Yes, in some years the average is hit spot on, but that's actually not a normal occurrence.

I know I'm parsing words, but I think this is where the confusion comes as to "how can this happen?" The simple fact of the matter is that when we plan our long term lives: cities, parks, roads, infrastructure, etc., we have to be ready for events far away from the mean. Because, they are normal occurrences.

The sad fact is that for this not-unprecedented high-precipitation event, the dam design was a failure. The main spillway could not handle outflows well within range. The emergency spillway basically couldn't handle anything. They designed that emergency spillway on a wish, a wish it would never get used. That's almost criminal. To see the way the earthen substrate was caving backwards towards the spillway structure astounds me. It looks like it was built on compacted earth. I'd say some swear words here, but I better stop.

The good news is they put caution to the wind on the main spillway and just let it do its thing as the tailrace deteriorates. At least that deterioration seems to be staying far away from the main control structure. Hopefully, the main spillway can handle the expected inflow of the next rain event.

The main spillway has handled high volumes in the past. After one heavy series of storms, they ran it at 160,000 cf/second. That's a little higher than the downstream levees are rated (150,000 cf/second). It's not clear why the main spillway failed this time, as opposed to previous high discharge events. What is clear is that the emergency spillway was not designed properly and will have to be redesigned based on this experience. Had the hill eroded to the point the dam water pushed through the hill below the concrete lip, the entire dam could have failed.

My guess is the lake level will be lowered significantly for several years while engineers and contractors rethink and rebuild the emergency spillway. That defeats the benefit of a wet winter to the stored water deficit.