'Hazardous Situation' at Storm-Damaged Dam, Tallest in US

BoxheadTim wrote: In reply to alfadriver: From some news reports I saw, the damaged area of the main spillway had been repaired fairly recently. Something caused turbulence in the repaired area, resulting in the damage we're seeing now.

The part that seems to be overlooked is the power of the turbulence. That's a LOT of water, and it did not have to move those slabs of concrete much before what was underneath them really broke down.

Given the heights of the sides, the depth that it was designed to was pretty close- given the pictures that we've seen. So the volume flow estimates were not bad. It's just the strength of the flow that seems underestimated- or completely falsely done at the time.

As for the rest of the comments- poor area- CA struggled through drought for years, and it all comes back at once, which it can't handle. Ugh.

That is a pretty big dam failure. I hope they come up with a decent dam solution, otherwise people are going to be asking some seriously tough dam questions. After the long drought the last thing they need is more dam problems. Too bad the dam engineers didn't fix the dam problems when water levels were at an all time low over the last few years. They couldve turned their dam lemons into dam lemonade. Should I keep going?

In reply to gearheadmb:

Dam punny, are we?

One interesting tidbit is that this dam is something like 50 years old and it's the first time ever that they had to use the emergency spillway. So from that perspective I'm not surprised that things went a bit haywire.

https://www.youtube.com/embed/SBQ-vW6rz_Y?ecver=1

As someone that comes from a state with salt and frost heave, all I could think up is this:

How close to the dam do people actually live? Why would anyone buy a house situated just downstream of a massive earthen dam that is really, really old in a state known for earthquakes? You'd think it would already be a ghost town down there.

I wonder if this will change their mind about succeeding from the union with a FEMA call.

BoxheadTim wrote: In reply to gearheadmb: Dam punny, are we? One interesting tidbit is that this dam is something like 50 years old and it's the first time ever that they had to use the emergency spillway. So from that perspective I'm not surprised that things went a bit haywire.

But it was the failure of the main spillway that made the emergency spillway a necessity, wasn't it? Anything with the name "emergency" in it is obviously not intended for regular use.

pinchvalve wrote: How close to the dam do people actually live? Why would anyone buy a house situated just downstream of a massive earthen dam that is really, really old in a state known for earthquakes? You'd think it would already be a ghost town down there.

I'm not an expert, but they're evacuating everyone downstream on the river. It's not a concern of dam breaching, but more of an uncontrolled flooding along the riverbanks... They're evacuating several miles downstream, so it's possible that even considering this is a 100 year weather pattern, the potential for flooding in this area was presumably pretty low to begin with.

Basically, something something it's a complex sequence of unfortunate events that leads to catastrophe rather than a single, defined issue.

Keith Tanner wrote:

BoxheadTim wrote: In reply to gearheadmb: Dam punny, are we? One interesting tidbit is that this dam is something like 50 years old and it's the first time ever that they had to use the emergency spillway. So from that perspective I'm not surprised that things went a bit haywire.

But it was the failure of the main spillway that made the emergency spillway a necessity, wasn't it? Anything with the name "emergency" in it is obviously not intended for regular use.

Again, I could be wrong, but there isn't a 'main' spillway per se. This spillway is the only one intended to be used, and it's only used in emergency situations. In fact, it had never been used up to this point, where the Sierras are getting HAMMERED with legendary snow and rain amounts.

There's the concrete spillway which has been used before, then there's a designated overflow route that (I believe) is considered the emergency spillway. It's the one running through trees and dirt that they're not really very happy about using.

pinchvalve wrote: How close to the dam do people actually live? Why would anyone buy a house situated just downstream of a massive earthen dam that is really, really old in a state known for earthquakes? You'd think it would already be a ghost town down there.

We moved to SE Idaho well after the Teton Dan break. But that flood went many, many miles. And it was a much smaller body of water than this one is. Then again, there are a LOT of people who live under the Palisades Reservoir.

Here's the History Channel's quick history of the Teton Dam failure http://www.history.com/topics/us-states/idaho/videos/engineering-disasters-teton-dam

Keith Tanner wrote:

BoxheadTim wrote: In reply to gearheadmb: Dam punny, are we? One interesting tidbit is that this dam is something like 50 years old and it's the first time ever that they had to use the emergency spillway. So from that perspective I'm not surprised that things went a bit haywire.

But it was the failure of the main spillway that made the emergency spillway a necessity, wasn't it? Anything with the name "emergency" in it is obviously not intended for regular use.

Pretty much, yes.

"On October 17, 2005 three environmental groups filed a motion with the Federal Energy Regulatory Commission urging federal officials to require that the dam’s emergency spillway be armored with concrete, rather than remain as an earthen spillway and that it did not meet modern saftey standards. "In the event of extreme rain and flooding, fast-rising water would overwhelm the main concrete spillway, then flow down the emergency spillway, and that could cause heavy erosion that would create flooding for communities downstream, but also could cause a failure, known as 'loss of crest control.'" FERC and water agencies responsible for the cost of the upgrades said it was unnecessary and concerns were overblown."

Some poor engineer is as about to get fired.

I ahve been following this on Pirate.

This is the real issue

If that undermines the concrete lip enough for it to let go, that's a 30' wall of water.

I don't remember how I ended up watching this a few months ago (wandering around on Youtube I guess) but here's a quick video on the dam construction:

https://www.youtube.com/watch?v=p_5udzKfLQM

Usually, the main spillway is used to regulate pool level. They use it to draw the lake down when storms approach so that water can be released in a controlled manner, over a period of days or weeks, to stop downstream flooding.

The emergency spillway is a low spot in the dam for overflow when the main spillway fails or cant keep up with the influx of water. They are never used willingly. In this instant, the main spillway has failed and been closed to stop a dam failure. The lake level has now topped the emergency spillway. The problem with the emergency spillway is there is no way to regulate the flow. They seldom have control gates. Once the lake tops the emergency spillway, they can't stop it or control it. It's going to dump all the water, all at once. The emergency spillway is topped, there is more rain coming. They can't stop the flooding that is going to happen. Hence the evacuation.

Just to add insult to injury, there are reports of erosion problems with the emergency spillway. They can't stop them, they can't shut it off for repairs. They better be doing emergency repairs to the main spillway so they can put it back in service ASAP to draw the lake levels below the emergency spillway.

It's my understanding they're using the main spillway anyhow to get that level down. Sure, it's eroding further but it's preferred to having the emergency one undermine the dam.

It looks like they are being reasonably successful at lowering the level. They want to drop the level 50 feet in order to do repairs (after the winter rains I would assume). The huge releases are causing flooding issue down stream as you can imagine.

For those who wonder why they did not bother to fix the dam before hand. The state has priorities, and would rather spend on something like this:

California's bullet train is hurtling toward a multibillion-dollar overrun, a confidential federal report warns

(almost every aspect of which is a complete fail and wildly over budget... but lets push ahead shall we...)

Osterkraut wrote: "On October 17, 2005 three environmental groups filed a motion with the Federal Energy Regulatory Commission urging federal officials to require that the dam’s emergency spillway be armored with concrete, rather than remain as an earthen spillway and that it did not meet modern saftey standards. "In the event of extreme rain and flooding, fast-rising water would overwhelm the main concrete spillway, then flow down the emergency spillway, and that could cause heavy erosion that would create flooding for communities downstream, but also could cause a failure, known as 'loss of crest control.'" FERC and water agencies responsible for the cost of the upgrades said it was unnecessary and concerns were overblown." Some poor engineer is as about to get fired.

Those damn (pun intended) environmentalists always sticking their noses in other people's business and making expensive regulations and recommendations.

NEALSMO wrote: Those damn (pun intended) environmentalists always sticking their noses in other people's business and making expensive regulations and recommendations.

They are also responsible for the Delta Smelt issue: http://news.nationalgeographic.com/2015/04/150403-smelt-california-bay-delta-extinction-endangered-species-drought-fish/ which is requiring California to literally dump a large percentage of it's fresh water out to sea (through the delta). I think it's something like 20% (not sure). Needless to say, this is a HUGE problem.

Of note, the farming of almonds is not helping either, they take a huge amount of water to grow.

java230 wrote: I ahve been following this on Pirate. This is the real issue If that undermines the concrete lip enough for it to let go, that's a 30' wall of water.

Thanks, that's the best illustration I've seen of the issue, and I can see how the choppers droppin' rocks would actually help. Look at how much erosion there is already! That road is toast as is the parking lot.

There is a decent sized town right below that dam, good percentage of the 200,000 they are telling to evacuate reside there. There is not as much concern about the whole dam going as there is the emergency spillway failing. If that part goes, my understanding is that it drops the lake 30 feet. We are talking about a 15,000 acre lake, so that is about 45,000 acre feet

Some of the nicest roads in California up above that damn dam, Feather River Canyon has nice little two lane that winds down to the level of the dam. Have some pictures of a neat little red Bugeye Sprite upside down in the ditch next to that road around someplace.

Keith Tanner wrote: It's my understanding they're using the main spillway anyhow to get that level down. Sure, it's eroding further but it's preferred to having the emergency one undermine the dam.

They are running the main spillway at max rated output, 150k cfs.... Also running the powerhouse outlet at max capacity. Input has slowed now and levels are dropping slowly.

its gonna need some serious repairs too.

They are still running main spillway at full tilt.

Here is the "patch job" they did in 2013, thats where the hole opened up again.

Toebra wrote: If that part goes, my understanding is that it drops the lake 30 feet. We are talking about a 15,000 acre lake, so that is about 45,000 acre feet.

Actually, 450,000 acre feet.