How could they quickly repair the damage?

They can't. A simple patch would be point of future weakness - just a way of deferring the next catastrophe. At best, they'd have to completely rebuild the spillway and put in a substratum (sorta like they do with highways) that would make the spillway more resilient.

Which, one might argue, would simply be deferring the next catastrophe a bit longer than you would by just patching up the hole.

Was this a design flaw and/or a result of continual pounding of the water?

Wonder how many more around the country could suffer the same type of catastrophic failure?

Somewhere it said the 'emergency spillway' hadn't been used in the history of the dam, so I doubt it was a wrong design.

Just an extraordinary amount of water from Mother Nature is about it.

quote:

Originally posted by Il Cattivo:
They can't. A simple patch would be point of future weakness - just a way of deferring the next catastrophe. At best, they'd have to completely rebuild the spillway and put in a substratum (sorta like they do with highways) that would make the spillway more resilient.

Which, one might argue, would simply be deferring the next catastrophe a bit longer than you would by just patching up the hole.

Could they rebuild that section as a bridge-type structure with a steel backbone? There is a section of the Main Canal in Germany that actually crosses over a river--could that type of engineering be adopted for the spillway?

flashguy

I'm guessing that if the water level stays were it is now, they would have time to fix it. But with the sudden and pretty emphatic end to the CA drought (or at least a significant intermission in it), what's the chance of that happening? If Northern CA get's hammered with more storms, they're going to have to let the reservoir drain, which is going to worsen the damage.

I am not an engineer - I can't even build a halfway decent sand castle.

But watching this story is absolutely fascinating.

I hope they get it figured out.

Mother Nature does things on her own terms.

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quote:

Originally posted by sourdough44:
Somewhere it said the 'emergency spillway' hadn't been used in the history of the dam, so I doubt it was a wrong design.

Just an extraordinary amount of water from Mother Nature is about it.

The picture with the hole in the concrete is the "Main Spillway". The emergency spillway is to the left of the main spillway.

quote:

Originally posted by Sig209:
I am not an engineer - I can't even build a halfway decent sand castle.

But watching this story is absolutely fascinating.

I hope they get it figured out.

Mother Nature does things on her own terms.

---------------------------------

Yes she does. When she wants it and how she wants it. Just look at how Niagara Falls has changed over the years.

I guess cutting another channel to divert the water while they fix this isn't feasible.

Anyone have an idea how thick the concrete is on the spill way?

quote:

Originally posted by Il Cattivo:
They can't. A simple patch would be point of future weakness - just a way of deferring the next catastrophe. At best, they'd have to completely rebuild the spillway and put in a substratum (sorta like they do with highways) that would make the spillway more resilient.

Which, one might argue, would simply be deferring the next catastrophe a bit longer than you would by just patching up the hole.

I'm not an engineer so bear with me. Maybe spillways constructed like this are inviting disaster or is this the only way it can be done?

quote:

Originally posted by Sig209:

...Mother Nature does things on her own terms.

---------------------------------

Is it practical/cost effective to build for something with a very small chance of happening? Maybe our engineers can explain.

quote:

Originally posted by Sigmund:

quote:

Originally posted by Sig209:

...Mother Nature does things on her own terms.

---------------------------------

Is it practical/cost effective to build for something with a very small chance of happening? Maybe our engineers can explain.

A great point. Think of the Fukashima, Japan nuclear disaster. I am sure that was 'well built'.

What was the chance of an earthquake AND a tsunami happening effectively simultaneously.

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quote:

Originally posted by flashguy:
Could they rebuild that section as a bridge-type structure with a steel backbone? There is a section of the Main Canal in Germany that actually crosses over a river--could that type of engineering be adopted for the spillway?

Sure, but I'd worry that it would accelerate the flow of water into the bottom of the structure, which would create another erosion hazard. As a temporary fix to carry water over the spillway until the spillway can be repaired or replaced, it would be kind of expensive and elaborate.

The basic idea is to avoid seams, which are weak points in resisting erosion, and angles, which increase the impact of the water on different parts of the concrete lining.

RCBS is located in that area. I hope they don't have any damage.

quote:

Originally posted by ulsterman:
I'm not an engineer so bear with me. Maybe spillways constructed like this are inviting disaster or is this the only way it can be done?

I'm not either, I just have a degree in planning.

The theory is that you're putting greater constraints on large forces in order to prevent them from doing what they would naturally do. This would tend to lead to catastrophic failures because there's no outlet for those forces - the forces keep building up until they make an outlet through the constraints. When an unstoppable force finds its way through an immovable barrier, it tends to be a pretty spectacular event.

The alternative would be to accept smaller floods that happen more often since they should be easier for people to adapt to than the occasional megaflood. The problem tends to be economic and therefore political - the delivery of water becomes more variable (which, along with constant minor flooding, is the problem that dams are supposed to solve), there's less you can do with land along the river, and all of that valuable land along the dam is no longer all that valuable since it's no longer man-made "lakefront" property.

Doesn't appear to be any fix that will withstand the pounding of Mother Nature.

I appreciate the education.

quote:

Originally posted by ulsterman:


Anyone have an idea how thick the concrete is on the spill way?

Judging from the picture of the hole with the men in it, it appears to only be about 1 1/2' - 2' thick.

CNN actually had a very good diagram of the dam and spill ways.

Anyone who knew what they were doing could see that Fukashima was a disaster waiting to happen. Tsunamis and earthquakes usually happen together. There's a known subduction zone twenty miles off the coast. That WAS going to generate a large earthquack/tsunami combination at some point. The only question is when. This has happened to Japan before and is a known part of their history.

It's known that nuclear plants need to maintain grid power to maintain the cooling loop pumps, and that grid power may be lost in an earthquake. To this end, they installed backup generators. But they put them low enough to be inundated and knocked out. Who thought this was a good idea?

quote:

Originally posted by Sig209:

quote:

Originally posted by Sigmund:

quote:

Originally posted by Sig209:

...Mother Nature does things on her own terms.

---------------------------------

Is it practical/cost effective to build for something with a very small chance of happening? Maybe our engineers can explain.

A great point. Think of the Fukashima, Japan nuclear disaster. I am sure that was 'well built'.

What was the chance of an earthquake AND a tsunami happening effectively simultaneously.

---------------------------

My friend is Army Corp of Engineers out of Sacramento. While this isn't their dam, they are monitoring the situation closely. He's not impressed with DWR's response.

Just to clarify, the large failure in the concrete spillway is alarming and of concern, my understanding is that DWR can live with the broken spillway, even at increase flow rates (100,000 cfm). Yeah, it's gnarly and water is flying all over the place and it will be expensive to fix. On one picture, you can see a massive rock formation now exposed. I'm not a geologist nor engineer, but I'd imagine solid rock is a good sign.

The bigger concern was the boil that developed below the concrete ridge of the emergency spillway just to the left of the regular spillway. If for some reason if that were to fail, then they'd lose a good earthen portion of the dam and hence the fear of mass flooding and forced evacuation. So the goal is make a quick repair to the boil area so that the emergency spillway maintains its integrity. Another storm is slated for late Wednesday. I'd imagine they'll continue high flow rates out of the regular, concrete spillway to avoid putting pressure on the emergency spillway.

The dam was build/operational in 1963 I believe.