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Reilly
Mountain climber
The Other Monrovia- CA
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Lemme get this straight, the guys on the ground have safety harnesses on while the guys
above do not? How does that logic work? No wonder this will take forever.
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August West
Trad climber
Where the wind blows strange
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Apr 10, 2017 - 11:00am PT
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http://www.mercurynews.com/2017/04/07/oroville-dam-dwr-unveils-plans-to-replace-damaged-spillway/
As the department switches into recovery mode, it’s looking at three phases going forward, with about 60 percent of the design complete, Croyle said. DWR plans to repair and replace the top part of the spillway by next winter, allowing for a total outflow of 270,000 cfs, said Jeanne Kuttel, DWR chief engineer.
That includes drains, walls and some foundation rock, in order to meet modern dam design standards, Kuttel said. The next phase will focus on the lower spillway, which will be replaced with stronger concrete. Roller-compacted concrete, or RCC, is used at dams across the nation, she said. The department expects to have bottom portion of the spillway able to handle 100,000 cfs by Nov. 1, so that would be the maximum capacity for the structure for the season.
At an afternoon press briefing, DWR Acting Directory Bill Croyle said the lower portion of the spillway would also be repaired by Nov. 1 to withstand a maximum outflow of 100,000 cubic-feet per second.
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Next year, the department plans to bring the lower chute capacity to match the top portion’s capacity of 270,000 cfs, Croyle said.
The third phase will involve reinforcing the emergency spillway with RCC.
I didn't think they would be able to fully repair by this fall. Will be interesting to see how much they lower the lake level since the main spillway will only be able to handle (assuming the emergency repairs are a success) 100,000 cfs and they won't want to use the emergency spillway.
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Apr 10, 2017 - 07:43pm PT
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In this NPR interview, UC Davis Geology professor Eldridge Moores (John McPhee's guide for Assembling California) explains that the Oroville Dam main spillway was built on weathered, incompetent rock. Eldridge is a world renowned expert on Ophiolite Sequences, including the Smartville Complex.
They did not anchor the spillway in fresh rock.
It seems to me that even a student of geology could have told them that they were going to have an erosion problem here.
https://ww2.kqed.org/science/2017/04/07/how-incompetent-rock-led-to-the-oroville-dam-crisis/
Photos from the DWR website of ongoing geologic characterization using continuous core drilling at the emergency spillway...
In search of the illusive Saprolite ;-(
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healyje
Trad climber
Portland, Oregon
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Apr 12, 2017 - 08:24am PT
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Seriously? C'mon, it doesn't require public records to figure out what happened - it's not rocket science - it was completely shite, lowball design and construction and the state's refusal to do anything about it ever since. This was all laid out well enough in the past when those evil environmentalists tried to get the dam fixed back in 2005.
As to the announced fixes, the publicly released remediation documents are more than clear and the the plans for both spillways are well within today's engineering norms.
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Apr 12, 2017 - 09:21am PT
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The NewsDeeply article claims that the geologic material beneath both spillways that failed is Saprolite (chemically weathered bedrock) and that the vulnerability of this material to erosion was not recognized back in the '60s...that sounds like a croq of sh*t
Saprolites have traditionally been associated with iron-rich bedrock that has been chemically weathered in place to thick soil in tropical climates +/-30 degrees latitude of the equator...
The Saprolite did it! ;-(
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Apr 12, 2017 - 09:30am PT
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I think the emergency spillway came dam(n) (no pun intended) close to failure...which would have been an enormous disaster...this is why there are so many drill rigs up there doing geologic characterization right now to better understand the 3D distribution of "soft" bedrock and the vulnerability of the emergency spillway to failure.
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August West
Trad climber
Where the wind blows strange
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Apr 12, 2017 - 11:04am PT
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DMT,
That they freaked out at what they saw and ordered an evacuation was reasonable. Better safe than sorry.
I don't think the entire 700' dam was in danger of collapsing in a matter of hours like the Grand Teton dam did back in the 70's.
When they went back to using the main spillway, the lower part suffered a lot of damage but the upper part never eroded back upstream toward the crest.
The emergency spillway is off to the side of the dam on top of a big hill. The 30 foot concrete spillway could have suddenly collapsed and it would have started to erode the soft material away (like what happened to the lower part of the main spillway) until it got down to sturdier rock. However, I'm not sure if it would have eroded over to the main dam or not. But if it did, I would imagine that it would have taken at least days, not hours. After the first surge of water from the 30' concrete spillway collapsing, there would have been time to evacuate.
But the secrecy is BS. I'm wondering if the price tag for repairs is going to be secret? Wouldn't want ISIS to know how badly tax payers are being hit for a poorly engineered dam.
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Ksolem
Trad climber
Monrovia, California
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Apr 16, 2017 - 11:02am PT
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So it looks like the cost of 118 miles of bullet train could fix this dam about 230 times. Damn!
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Brandon-
climber
The Granite State.
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Apr 16, 2017 - 11:26am PT
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Kiewit will probably get the contract, they're undertaking huge projects all around N America.
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Ksolem
Trad climber
Monrovia, California
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Apr 16, 2017 - 12:03pm PT
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I've been thinking about that emergency spillway. Let's call it a "back-up" spillway. All of a sudden we have a climbing analogy.
I started climbing at the Gunks. My mentor was a French Canadian guy. For the most part Clog hex nuts, stoppers and the occasional fixed pin were the tools of the day. When he was setting up an anchor he would insist that his back-up piece was at least as good as the rest of the anchor. "Doesn't make much sense to have it the other way around now, does it?"
Hmmm.
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neebee
Social climber
calif/texas
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Apr 17, 2017 - 09:32pm PT
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hey there say, ... always enjoy seeing this pop back up...
also, say DMT... thanks for the other link...
really ENJOYED that!!
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Kalimon
Social climber
Ridgway, CO
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Apr 18, 2017 - 07:20pm PT
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$275,400,000.00 is pretty cheap in expensive California.
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healyje
Trad climber
Portland, Oregon
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Apr 19, 2017 - 02:13pm PT
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And DWR has refuted key points of that independent report and is of course doing their own investigation. Boldly denying the concrete was too thin and that there wasn't enough rebar is just plain stupid. I'd have given top DWR officials a pass if it weren't for ignoring the warnings in 2005 and now these comments which by themselves should cause the their removal.
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Apr 19, 2017 - 02:39pm PT
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...and don't forget that Saprolite had not been recognized as a vulnerability back in the 60s ;-(
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Charlie D.
Trad climber
Western Slope, Tahoe Sierra
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Apr 21, 2017 - 07:39am PT
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^^^ Yikes, in the end it all comes down to some humans making decisions or not.
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August West
Trad climber
Where the wind blows strange
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Apr 21, 2017 - 09:20am PT
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DMT. I agree. They built a cheap emergency spillway on the assumption it wouldn't ever be used.
Given their conflict of interest, they should not have had the final say on beefing up the spillway in 2005.
And it should be criminal to so favor ag interests over flood safety for 200,000.
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