Author Topic: Possible dam failure, flood, near Sacramento  (Read 1447 times)

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Offline Soldier of FORTRAN

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Possible dam failure, flood, near Sacramento
« on: February 13, 2017, 03:46:40 AM »
The Oroville Dam's spillways are near failure, spurring an evacuation order for 100k+ on Sunday afternoon. 



Currently, water's below emergency levels and there's opportunity for repair work but in a few days, they're due to get a lot more rain! 

Picture below, the dam and the spillway.



Here's two recent photos of the spillway's deterioration:



There's also the emergency spillway which is damaged.  It's basically just the hillside further to the left:
 



Weather forecast:




Photo of evacuee:




Here's hoping this is the worst of it

Edit:. I should probably add that there was fear of imminent collapse earlier but we lucked out there
« Last Edit: February 13, 2017, 08:44:38 AM by Soldier of FORTRAN »
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Offline Ah.hell

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Re: Possible dam failure, flood, near Sacramento
« Reply #1 on: February 13, 2017, 09:49:28 AM »
I grew up in the evacuation zone, much of my family is still there.  My cousins even live on the road noted in the picture below, their in the foothills though. 

Something to note, the reason the flood zone is so large, from wiki:

Quote
Over the millennia, the valley was filled by the sediments of these same ranges, as well as the rising Sierra Nevada to the east; that filling eventually created an extraordinary flatness just barely above sea level; before California's massive flood control and aqueduct system was built, the annual snow melt turned much of the valley into an inland sea.


Offline estockly

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Re: Possible dam failure, flood, near Sacramento
« Reply #2 on: February 13, 2017, 11:27:24 AM »
The eminent collapse they feared was of the thirty feet of concrete atop the emergency spillway. Not the dam itself.


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Offline Belgarath

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Re: Possible dam failure, flood, near Sacramento
« Reply #3 on: February 13, 2017, 12:00:15 PM »
The eminent collapse they feared was of the thirty feet of concrete atop the emergency spillway. Not the dam itself.


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Was it the concrete or was it the dirt emergency spillway?  The normal spillway seems to be ok (except the huge hole 1/2 way down)
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Offline Ah.hell

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Re: Possible dam failure, flood, near Sacramento
« Reply #4 on: February 13, 2017, 12:20:56 PM »
My understanding it the fear was that they emergency spillway would collapse.  I'd imagine that they were worried about that because of fear the concrete spillway would also collapse?

Offline estockly

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Re: Possible dam failure, flood, near Sacramento
« Reply #5 on: February 13, 2017, 01:23:47 PM »
My understanding it the fear was that they emergency spillway would collapse.  I'd imagine that they were worried about that because of fear the concrete spillway would also collapse?

There is a 30-foot high concrete section of the rim of the dam (where you see the water flowing over in the videos) just above the emergency spill way (which is basically dirt).  The danger is that the emergency spillway could have (or still could with more rain) erode enough that part of the dam could collapse sending a 30-foot wall of water into the valley, which is much better than the 800-900-foot wall of water some in the press were discussing.

But a 30-foot wall of water is nothing to laugh at.



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Offline Soldier of FORTRAN

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Re: Possible dam failure, flood, near Sacramento
« Reply #6 on: February 13, 2017, 01:45:57 PM »
Yeah, it's the emergency spillway that's of concern. 

The articles I read glossed over the technical details but it sounds like the emergency spillway is taking damage right at the top, and the bedrock's a little deep.  If it goes, not only could the entire thing just disappear but the depth of that notch in the hillside could drop quite a bit.  This is the threat which caused them to issue an evacuation order. 

Whereas the main spillway's failing further down and the bedrock's near the surface so the concern here's mainly the repair costs. 

The actual dam's not under threat.  I've read that if that went, it'd destroy Sacramento. 
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Offline teethering

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Re: Possible dam failure, flood, near Sacramento
« Reply #7 on: February 13, 2017, 01:46:56 PM »
DO NOT WANT :(

Offline Soldier of FORTRAN

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Re: Possible dam failure, flood, near Sacramento
« Reply #8 on: February 13, 2017, 01:51:40 PM »
From yesterday:

Every soup ladled to the hungry, every blanket draped over the cold signifies, in the final sense, a theft from my gigantic paycheck.

Offline estockly

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Re: Possible dam failure, flood, near Sacramento
« Reply #9 on: February 13, 2017, 03:31:51 PM »


This is after the water levels dropped a bit. The curved-top concrete is where the water was spilling over. The emergency spill way is the ground below that you can see has been seriously eroded. The fear is that erosion would weaken the earth supporting the concrete wall. A collapse would release the top 30 feet of water from the lake all at once. The 800-900 foot dam is not at risk.

The frantic fight to keep the Oroville Dam crisis from turning into a catastrophe - LA Times


http://www.latimes.com/local/lanow/la-me-ln-oroville-dam-crisis-20170213-story.html
« Last Edit: February 13, 2017, 06:40:27 PM by estockly »
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Offline daniel1948

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Re: Possible dam failure, flood, near Sacramento
« Reply #10 on: February 13, 2017, 03:48:04 PM »
James Thurber. The day the dam broke.

(click to show/hide)
« Last Edit: February 13, 2017, 03:50:55 PM by daniel1948 »
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Offline wastrel

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Re: Possible dam failure, flood, near Sacramento
« Reply #11 on: February 13, 2017, 04:00:50 PM »
I'm confused about the purpose of posting that...

Offline Crash

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Re: Possible dam failure, flood, near Sacramento
« Reply #12 on: February 13, 2017, 05:03:13 PM »

  I took this screen shot from google maps where I saw the dam emergency spillway starting to fail.  Where the concave buttress  ends, there is just a curb at the water line.  Yesterday evening when the evacuation order was announced the parking lot was submerged and the water was flowing over the curb.  Behind the curb is unconsolidated landfill and it was starting to wash away.    There was a live helicopter feed until sun down and it looked bad but this morning it looked much better. 
  What the main spillway looks like now is a mystery because it has been flowing  since last Tuesday. They have yet to stop the flow again to have a look. 
  I'm beginning to wonder what Shasta Dam is doing right now.  Old timers like to talk about the days before Shasta dam when the whole valley flooded routinely.  Quaint old homes in the older parts of Sacramento are often called  "high water bungalows" because the main living space and front porch is on the second floor.  They are a vestige from when there was always flooding. 

Offline Johnny Slick

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Re: Possible dam failure, flood, near Sacramento
« Reply #13 on: February 13, 2017, 05:31:22 PM »
Well, working out a lot better than the last time a California dam burst, at least.
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Offline Ah.hell

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Re: Possible dam failure, flood, near Sacramento
« Reply #14 on: February 13, 2017, 05:40:17 PM »
I will always mention when this comes up, Mulholland, the engineer responsible for St Francis Dam and the theft of the Owens Valley water for LA, was also involved in 2 other dam failures.

Also, not the last time a damn failed in CA.

https://en.wikipedia.org/wiki/Baldwin_Hills_Dam_disaster 1963.
« Last Edit: February 13, 2017, 05:43:52 PM by Ah.hell »

 

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