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Dingus Milktoast

Trad climber
Minister of Moderation, Fatcrackistan
Mar 26, 2017 - 08:20am PT
Here's a 'tuned spillway.' My thinking: the loops effectively extend the length of the spillway, widening the gap between the hills. However the engineers anticipated potential turbulence by doing that and so also designed in dampeners, and other means to vary the distance the water tumbles into the spillway chute. Finally the chutes themselves are like a car exhaust manifold, further smoothing out the fluid turbulence such that if you look at the water flow down stream, its super-smooth.

Contrast this with Oroville dam spillway turbulence. Admittedly this is a much lower flow rate. This is Stony Creek over in NorCoast range.



Pretty fascinating design. Check out the stair steps and other 'tuning' features designed to take out standing waves.




Dingus Milktoast

Trad climber
Minister of Moderation, Fatcrackistan
Mar 26, 2017 - 08:26am PT
And a different kind of dam to go with the cool spillway feature- Stony Gorge





DMT
eeyonkee

Trad climber
Golden, CO
Mar 26, 2017 - 01:11pm PT
Damn! Like those dam pictures, DMT.
Dingus Milktoast

Trad climber
Minister of Moderation, Fatcrackistan
Mar 28, 2017 - 06:08pm PT
Pretty fascinating story about that spillway pictured above.

Summary: Built in 3 stages, beginning in 1909. The arches were intended to lengthen the width of the spillway to accommodate anticipated flood discharge of 10,000 cfs. After the first stage was completed a flood severely damaged the lower race of the spillway, eroded down to the "blue shale" bedrock and came within 60 feet of back digging its way to the foot of the spillway structure itself. Sound familiar?

Because the dam was designed with a discharge capacity of 500 cubicfeet-per-second (cfs), which is well below the flood rate of 10,000 cfs, a spillway with a width of around 500 feet was needed; however, the natural width of the saddle was only 300 feet. To provide this additional length, the spillway uses a series of nine piers and semicircular arched weirs. The piers are eight feet wide and the arched weirs are on a radius of 13-feet, 6-inches wide. The whole structure has a radius of 474 feet. This provides a total length of 459.9 feet. After reducing for curvature and “incomplete approach,” the available length is 414 feet


The foundation for the spillway is hard blue shale that is close to the surface of the ground; conglomerate is encountered only at the north abutment

The spillway, on this contract, was completed in July 1910; however, it wasn’t finished. Read on.


At the end of February 1911, it rained, and rained, and rained for seven days leaving behind an accumulation of nearly six inches (5.95) that, by March 7, 1911, had filled the reservoir to overflowing. The spillover caused a maximum flow of 1,820 fps over the crest of the spillway that lasted for 72 hours

The volume and force of the spilled water washed away the surface of the creek bed below the spillway to expose the blue shale. Upon exposure, the force of the water cut deep channels in the shale back to within sixty feet of the apron of the spillway. The water also washed away surface dirt along the sides of the channel exposing the underlying conglomerate. In other words, the storm ruined the spillway’s downstream channel, which resulted in another contract known as “East Park Spillway Extension.” Work on this extension began in August 1911 and the work was completed in December of the same year.

So they added the manifold structure.

The spillway extension is a giant half-funnel whose cone opens at the spillway and converges in “easy curves” to a conglomerate ledge 160 feet downstream that forms a channel whose output is a chute-like opening.
Due to eccentricities in the original spillway, water tended to build-up on the south wall creating run-off problems. To prevent that build-up in the spillway extension, three guide walls leading from the south piers direct water to the throat of the channel at the conglomerate ledge.

In 1914-1915, as a part of the
East Park Feed Canal/Rainbow Diversion Dam project, the spillway was permanently raised 18 inches and provisions made for adding removable 18-inch flash boards, for a overall maximum height increase of three feet. This construction also lengthened the slope and added steps to the piers. This additional height raised the reservoir’s capacity from 40,000 to 51,000 acre-feet.

Fascinating. Happened upon it fairly by accident as access to the reservoir in Colusa county is restricted. We just hopped the fence ;)

Lastly, the article mentions the conglomerate which certainly caught my eye:

The ridge through which the creek cut a gorge is conglomerate. Conglomerate is a clastic sedimentary rock that contains large (greater than two millimeters in diameter) rounded clasts. The space between the clasts is generally filled with smaller particles and/or chemical cement that binds the rock together.



Of particular interest to perhaps mungeclimber (and others)
The entire foundation, the report reads, “is of the hardest kind of conglomerate.”

The report is a PDF and so I can't link the images within but here is the report if you're interested:
http://stonyfordca.org/data/_uploaded/East%20Park%20article%20.pdf


Pretty cool, huh? That spillway is over 100-years old!

DMT
Dingus Milktoast

Trad climber
Minister of Moderation, Fatcrackistan
Apr 1, 2017 - 08:01am PT
Can't say I didn't see this coming. Me? DWR has proven less than competent by creating the Oroville Dam crisis to begin with. Now they want to hide their repair plan in plain sight, citing security concerns. Time we Californios started rolling DWR heads down the capitol halls and get some new blood in this agency....

Oroville Dam documents kept secret by state, federal officials

Citing potential security risks, state and federal officials are blocking the public’s ability to review documents that could shed light on repair plans and safety issues at crippled Oroville Dam.

One of the secret reports is a memo from an independent panel of experts brought in to guide state officials’ repair plans. Another confidential document is labeled a “Project Safety Compliance Report.”

The secrecy on the part of state dam operators prompted state Sen. Jim Nielsen to call for an immediate oversight hearing.

“I’m alarmed and on the verge of outrage. We have an absolute, significant public safety concern,” said Nielsen, a Republican who represents thousands of residents who were evacuated when it appeared the dam might flood the region in February. “We need to know what cause they have to believe that there’s such a (security) risk, or is that just cover-up?”


Of course its a cover-up. Faulty design, greedy water delivery customers and ineptitude on both dam operators and DWR emergency response all require secrecy to preserve the jobs of the dumb sonsabitches that created this emergency. Duh.

Read more here: http://www.sacbee.com/news/state/california/water-and-drought/article141963119.html#emlnl=Morning_Newsletter#storylink=cpy

DMT
T Hocking

Trad climber
Redding, Ca
Apr 1, 2017 - 08:26am PT
Stoopid Californians!

See more here; :)

http://www.bing.com/videos/search?q=Wet+Hare+1962&&view=detail&mid=A3C4D9B4C9DA5E786617A3C4D9B4C9DA5E786617&FORM=VRDGAR
rottingjohnny

Sport climber
Sands Motel , Las Vegas
Apr 1, 2017 - 08:51am PT
DMT.. sounds like a cover up but we all know any misdeeds will be handsomely rewarded...
Reilly

Mountain climber
The Other Monrovia- CA
Apr 1, 2017 - 09:10am PT
Nothing like living in a mature democracy, huh? Makes me feel warm and cuddly.
I'm wating for Guvnor Moonbeam's response, but I'm not holding my breath.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 1, 2017 - 09:41am PT
My contacts in the drilling and geophysical logging industries tell me that when they're not using the Oroville Dam main spillway there's a drilling and subsurface characterization campaign going on involving multiple drill rigs that are continuously coring the geologic material beneath the spillway and running optical televiewer logs in the boreholes to identify any other areas of decomposed or highly fractured amphibolite bedrock. In addition to inspecting and describing the rock quality characteristics of the core retrieved from the borehole, an optical televiewer is deployed in the borehole that records a high resolution, oriented, digital optical image of the borehole wall. This is critical information for any interim spillway modifications and the permanent spillway replacement design.





One of the latest concerns is the brown colored water flowing on the left side below the broken spillway. This may represent piping or undercutting and erosion of decomposed bedrock beneath the spillway. Photo posted on DWR website Mar 27, 2017.



This is what that area looked like before the shotcrete. Note highly sheared/decomposed bedrock on the left side corresponding to the where the brown colored water is flowing shown above. Similar sheared bedrock is also evident in the middle of the spillway where the guy is on his knees...


The extent of that sheared/decomposed bedrock material, especially if it extends back up to the top of the spillway, is a bit disconcerting.
Reilly

Mountain climber
The Other Monrovia- CA
Apr 1, 2017 - 10:03am PT
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.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 9, 2017 - 04:56pm PT
http://www.water.ca.gov/oroville-spillway/pdf/2017/a3186 Oroville Spwy Recovery_v5.pdf

Oroville Dam Main Spillway design concepts...


Current Emergency Spillway design being considered...

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 9, 2017 - 09:03pm PT
https://www.newsdeeply.com/water/articles/2017/04/07/oroville-disaster-may-have-been-caused-by-weak-soil-under-spillway

THE DESTRUCTION OF Oroville Dam’s main spillway in February likely occurred because it was built on highly erodible rock, according to several experts interviewed by Water Deeply. If confirmed by a forensic investigation now underway, rebuilding the spillway will require a much more expensive and time-consuming effort.
August West

Trad climber
Where the wind blows strange
Apr 10, 2017 - 11:00am PT
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.
...
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.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 10, 2017 - 07:43pm PT
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 ;-(
Dingus Milktoast

Trad climber
Minister of Moderation, Fatcrackistan
Apr 12, 2017 - 08:17am PT
Mums the word. Terrorists lurk don't you know. Sheesh. DWR is hiding the truth; no surprise. They knew of these troubles long ago, is my guess.

Gov. Jerry Brown’s administration is using federal security regulations written to thwart terrorism to deny public access to records that experts say could guide repairs to the Oroville Dam and provide insight into what led to the near catastrophic failure of its emergency spillway.

The administration also is blocking public review of records that would show how Brown’s office handled the February crisis at Oroville Dam that led to the two-day evacuation of nearly 200,000 Northern Californians.

Read more here: http://www.sacbee.com/news/state/california/water-and-drought/article143990719.html#emlnl=Morning_Newsletter#storylink=cpy

DMT
healyje

Trad climber
Portland, Oregon
Apr 12, 2017 - 08:24am PT
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.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 12, 2017 - 09:21am PT
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! ;-(
Dingus Milktoast

Trad climber
Minister of Moderation, Fatcrackistan
Apr 12, 2017 - 09:26am PT
What is obvious to me is the dam was far closer to failure than the press releases indicated. When the Butte County sheriff got a look at the actual situation he freaked the f*#k out and ordered the evacuations. The admins don't want the post-panic-anger pointed at them

DWR and the Brown Admin now know that this panic and the resulting Dam Fear threatens not only their control over the Oroville situation but also the massive Twin Tunnel L.A.-Water-Grab project as well.

Must not let the voters know... must not!

DMT
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Apr 12, 2017 - 09:30am PT
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.
August West

Trad climber
Where the wind blows strange
Apr 12, 2017 - 11:04am PT
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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