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svelte.
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February 10, 2017 at 8:48 AM #805498February 10, 2017 at 12:29 PM #805507
Hobie
ParticipantPlace your bets: Will they allow emergency spillway to take the water or will they open up the regular spillway 100%?
My bet is they will sacrifice the regular spillway.
Pretty wild situation.
February 10, 2017 at 12:37 PM #805508spdrun
ParticipantThe spillway isn’t the dam itself — it’s just a path for water to flow down. Is there any actual risk to using the regular spillway, other than the need for concrete repairs after the lake is drained?
February 10, 2017 at 1:56 PM #805509no_such_reality
ParticipantDo you think they’d say ‘we screwed the pooch’, even if did?
They say no. They say it’s just the spill way and not the dam, but look at his picture.
I’ll admit I’m not a dam engineer, but high energy water erodes really quickly through soft-ground.
Frankly, I’d be more concerned about the top break, here’s the closeup.
What happens when that spillway is gone from the top break to the bottom of the spillway and basically carved out like a flat wall?
February 10, 2017 at 2:59 PM #805511ParticipantI didn’t see pics of the top break. If I lived downriver from that thing, I’d be considering taking a vacation for a week or two.
February 10, 2017 at 3:20 PM #805512svelteParticipant[quote=no_such_reality]
What happens when that spillway is gone from the top break to the bottom of the spillway and basically carved out like a flat wall?
[/quote]Yeah, I’m pretty concerned that all of the hill downstream could erode away, then the erosion slowly works it way upstream.
As that happened more and more, less hillside would buttress the main earth dam and well you know what could happen when the weight of the water behind the dam overrules the buttress.
Still unlikely I would think, but if it keeps raining…
February 10, 2017 at 4:52 PM #805513svelteParticipant[quote=no_such_reality]Do you think they’d say ‘we screwed the pooch’, even if did?
[/quote]Probably not right away, but there would be a time when they would start evacuating folks. That happened in the 1980s. As I recall, the levee broke at night in the Marysville suburb of Linda.
The most common story I heard about the 1950s levee breach in Marysville proper was that everyone thought the levee was going to break in Yuba City (the two cities are on opposite sides of the river). Car dealers moved their new cars from YC to Marysville. Everyone evacuated YC. Then the levee broke in Marysville. Oy.
It is quite a sight to see when the water rises so high it is at the crest of the levee on both sides of the river. Gives me goosebumps. I go fill my gas tank.
February 10, 2017 at 4:54 PM #805514ParticipantYea, so much depends on the nature and structure of the bedrock anchoring the dam.
Water though is currently flowing into the reservoir at 130,000 CFS, the spillway is currently taking roughly 75,000 CFS out and the dam is basically full.
The dam is 700+ feet high and granted, it isn’t vertical, more like a 45 degree slope and it is water, but with erosion each CFS basically becomes a 8 lb piece of liquid sandpaper.
That’s a lot of sandpaper…
February 10, 2017 at 5:00 PM #805515svelteParticipant[quote=svelte]
The most common story I heard about the 1950s levee breach in Marysville proper was that everyone thought the levee was going to break in Yuba City (the two cities are on opposite sides of the river). Car dealers moved their new cars from YC to Marysville. Everyone evacuated YC. Then the levee broke in Marysville. Oy.
[/quote]I have it backwards – everyone evacuated ppl/cars to YC from Marysville in 1955…then the levee broke in YC. I should have remembered that, I’ve been in homes where the 1955 water line is still visible in closets in homes in YC. At the top of the closet.
February 10, 2017 at 11:22 PM #805516svelteParticipantGreat analysis here…
https://www.metabunk.org/oroville-dam-spillway-failure.t8381/
from the looks of the bedrock shown, looks like we are far from disaster.
February 11, 2017 at 11:07 AM #805520NotCranky
Participant[quote=svelte]Great analysis here…
https://www.metabunk.org/oroville-dam-spillway-failure.t8381/
from the looks of the bedrock shown, looks like we are far from disaster.[/quote]
Probably far from disaster. It looks like the main spill way has about 20 feet of decomposed granite between the manmade concrete chute and the bedrock. Unless at some point the concrete is laying on bedrock directly there is nothing to stop it from eroding all the way to the top. If the operators had to shut the spillway gates could the emergency spill way hold up? Just some questions.February 11, 2017 at 7:48 PM #805521ParticipantI suspect we will find out it’s currently going over the emergency spillway still slow. Looks like it’s doing a pretty good job of removing the overburden from the bedrock.
The water levels have, surprise, messed up their water release plans. They’ve slowed the main spillway and had to shutdown an auxiliary generator that took another 12000 CFS because the concrete broken out of the spillway is backing water up.
Good news its becoming sunny. For three days. Then the longer range forecast says basically 6 straight days of rain in Oroville and up land from the lake.
February 12, 2017 at 6:28 PM #805522ParticipantOroville being evacuated:
http://www.sacbee.com/news/state/california/water-and-drought/article132332499.htmlRight, and 45’s last tweet is whinging about fake news. No word about an actual situation that can potentially kill thousands.
February 12, 2017 at 6:38 PM #805523svelteParticipantA lot more than Oroville is being evacuated:
” The Yuba County Office of Emergency Services asked residents in the valley floor, including Marysville, a city of 12,000 people, to evacuate and take routes to the east, south, or west and avoid traveling north toward Oroville.”
https://www.yahoo.com/news/water-flow-slowing-over-emergency-spillway-tallest-us-204732388.html
“OROVILLE, Butte County — Butte County residents near Lake Oroville, including the entire town of Oroville and nearby regions, were ordered to evacuate Sunday evening after the emergency spillway next to the reservoir’s dam suffered a possible structural failure, officials said.
“There has been severe erosion of the emergency spillway and a possible structural breach that could send uncontrolled water down the stream,” said Chris Orrock, a spokesman with the California Department of Water Resources.Residents downstream from Lake Oroville to the Sutter County line were under mandatory evacuation order. Counties around the reservoir, the second largest in the state, down to Sacramento were warned about the possibility of flooding.
Department of Water Resources officials issued a statement just before 4:45 p.m. that the “auxiliary spillway at the dam was predicted to fail within the hour.”
“Traffic was bumper to bumper as residents of Oroville, Biggs and Gridley headed slowly out of the possible flood zone eastbound on Highway 162.
“This is very serious,” said Scott McClean, a spokesman with the California Department of Forestry and Fire Protection who was in the evacuation traffic. “From what I understand it’s the auxiliary spillway at a point of possible collapse. I’m just trying to get through traffic.”This is serious shit. Luckily the dam proper is not threatened, but still plenty of damage possible from collapse of the emergency spillway…
[img_assist|nid=26221|title=evacuation|desc=|link=node|align=left|width=567|height=473]
February 13, 2017 at 8:48 AM #805531ParticipantHere is a link to the best video image of what was going on at the emergency spillway. http://www.cnn.com/2017/02/12/us/california-oroville-dam-failure/index.html Flows there have receded now ,but by putting the damaged main spillway back on higher flows.
I wonder if there are pumps that could be brought onsite that can even begin to help move this amount of water? I pretty much doubt it. I guess they want to get it down 50 feet in case of new storm flow. Hope they can, and that it’s enough.
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