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Oroville Dam: Feds and state officials ignored warnings 12 years ago

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Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#21

Post by throwawaydbfif »

Holy shit look at the pictures. Both the regular and emergency spillway are heavily damaged and even more rain is expected Tuesday and in the coming weeks.

They shut the main spillway off because of damage and now they're running it at maximum flow because the emergency spillway is even more damaged. This feels every bit like a hail Mary pass to drain the lake as much as possible before the dam breaks. In another day or two they won't have any spillway left.

This dam is doomed, it seems like one of the rare times media is downplaying the risk... Probably because a lot of people are going to die :(

Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#22

Post by jnsaff2 »

wtallis wrote: post #15
jnsaff2 wrote: post #9

Earlier quoted context omitted.

The outflow hasn't changed so I'm not convinced that the flow over the lip has stopped. #armchairanalysis

The outflow seems to be the ~100000 cfs from the main spillway draining at full capacity, which they opened to 100% early in the evening to relieve the emergency spillway, in spite of the existing damage to the main spillway.

Thank you.

By the way there's an amazing book that has a very gripping account of the Glen Canyon Dam incident and Grand Canyon in general.

http://www.goodreads.com/book/show/15803144-the-emerald-mile

Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#23

Post by wiredfool »

lucaspiller wrote: post #12

> with flows of only 6,000 to 12,000 cubic feet per second In case anyone needs something to put that into perspective, an Olympic-size swimming pool holds around 35,000 cubic feet (1 megalitre) of water.

And the 100000cfs on the main spillway is 5 million lbs/sec.

Edit: oops. Off an order of magnitude.

Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#24

Post by the_mitsuhiko »

throwawaydbfif wrote: post #21

Holy shit look at the pictures. Both the regular and emergency spillway are heavily damaged and even more rain is expected Tuesday and in the coming weeks. They shut the main spillway off because of damage and now they're running it at maximum flow because the emergency spillway is even more damaged. This feels every bit like a hail Mary pass to drain the lake as much as possible before the dam breaks. In another day…

Why does the damage on the spillway matter? Is it fear of erosion if it does not go down the spillway?

Twitter says it's below the emergency spillway level now anyways so that damage shoukd not matter from what i understand.

Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#25

Post by yread »

I was just wondering about it the other day while researching the topic: why are there so many dam failures in the states?

https://en.wikipedia.org/wiki/Dam_failure#List_of_major_dam_...

Since 19th century US has the most (well, at least a lot) dam failures.

Is it because there are so many? Are they privately owned and the owners just count on declaring bankruptcy if it fails? Is it the engineering, the geology, the maintenance?

EDIT: Even such a major project like Hoover Dam was not done properly (it seems grouting curtains were not often used elsewhere) http://web.mst.edu/~rogersda/hoover_dam/Grout%20Curtain%20Fa...

Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#26

Post by the_mitsuhiko »

yread wrote: post #25

I was just wondering about it the other day while researching the topic: why are there so many dam failures in the states? https://en.wikipedia.org/wiki/Dam_failure#List_of_major_dam_... Since 19th century US has the most (well, at least a lot) dam failures. Is it because there are so many? Are they privately owned and the owners just count on declaring bankruptcy if it fails? Is it the engineering, the geology, the…

Is that not a result of have many dams, have higher chance of dam failure?

Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#27

Post by throwawaydbfif »

the_mitsuhiko wrote: post #24
throwawaydbfif wrote: post #21

Holy shit look at the pictures. Both the regular and emergency spillway are heavily damaged and even more rain is expected Tuesday and in the coming weeks. They shut the main spillway off because of damage and now they're running it at maximum flow because the emergency spillway is even more damaged. This feels every bit like a hail Mary pass to drain the lake as much as possible before the dam breaks. In another day…

Why does the damage on the spillway matter? Is it fear of erosion if it does not go down the spillway? Twitter says it's below the emergency spillway level now anyways so that damage shoukd not matter from what i understand.

The emergency spillway was used because the main one was already badly damaged so they shut it off. Now they're saying the damage to the emergency spillway is even worse than the main spillway so their turning the main spillway on full tilt to drain below the level the emergency spillway activates.

The thing is... They drained below the emergency spill way level many hours ago and it's off, but they're still running the heavily damaged main spillway at full tilt. I think it's a last ditch attempt to drain the lake before the dam fails, they just don't want to say it because everyone will panic

Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#28

Post by guelo »

This whole emergency evacuation makes no sense to me. They cut the flow on the main spillway from 100,000 to 50,000 cubic feet per second to push water to the emergency spillway and it immediately started dangerously eroding at only 6,000 to 12,000 cfps. So they cranked the main spillway back up to 100,000 cfps and as I type this the water level has dropped back down well below the top and the erosion danger has passed. The damage on the main spillway looks severe but not at immediate emergency levels. But in the mean time they have unnecessarily caused panic among 180,000 people with no warning and generated national headlines. It just seems like a lot of overreaction.

Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#29

Post by throwawaydbfif »

guelo wrote: post #28

This whole emergency evacuation makes no sense to me. They cut the flow on the main spillway from 100,000 to 50,000 cubic feet per second to push water to the emergency spillway and it immediately started dangerously eroding at only 6,000 to 12,000 cfps. So they cranked the main spillway back up to 100,000 cfps and as I type this the water level has dropped back down well below the top and the erosion danger has pass…

The damage to the main spillway is extreme. Look at the pictures, it's more of a semi controlled waterfall at this point. If erosion moves upstream on the spillway, which it eventually will, once it reaches the gates they will need to stop the spillway or risk the dam itself.

Their emergency spillway is already unusable, so this means just get everyone out and wait for the dam to blow once the main spillway erodes too far back

Re: Oroville Dam: Feds and state officials ignored warnings 12 years ago

#30

Post by Gargoyle »

the_mitsuhiko wrote: post #24
throwawaydbfif wrote: post #21

Holy shit look at the pictures. Both the regular and emergency spillway are heavily damaged and even more rain is expected Tuesday and in the coming weeks. They shut the main spillway off because of damage and now they're running it at maximum flow because the emergency spillway is even more damaged. This feels every bit like a hail Mary pass to drain the lake as much as possible before the dam breaks. In another day…

Why does the damage on the spillway matter? Is it fear of erosion if it does not go down the spillway? Twitter says it's below the emergency spillway level now anyways so that damage shoukd not matter from what i understand.

If the emergency spillway goes, that's 30ish lake-feet of water that would drain uncontrolled. That would likely wipe out a few towns down the river.

I think gp was getting to the fact that the main spillway is eroding as well, and it could reach a point where it was unusable. In that case, with significant rainfall expected in the next week and a good deal of snow melt to follow, there could be huge amount of water coming into the basin with no way to control the outflow, which could result in much worse flooding.

Hopefully that all can still be avoided. It's a bit dramatic to say it's inevitable. It's a possible scenario, but it's also possible the right plan avoids it.

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