Photo found here
Posted on 02/12/2017 4:26:47 PM PST by janetjanet998
Edited on 02/12/2017 9:33:58 PM PST by Admin Moderator. [history]
The Oroville Dam is the highest in the nation.
Agreed. The bandaids haven’t been effective. Maybe for occasional use, which is the history of this spillway, but the kind of use it has had this year (and will have again soon), that’s just not good enough. And really, considering the cost of a complete failure (people live and work downstream), a quality spillway is what’s needed.
It’s going to be a very interesting spring - they’ve done a fantastic job of getting things in order after the major wash-out. But the spillway will be used again, and they will have to work out how to rebuild/replace it.
Oh, I appreciate your input and observations. You and others have done a great job of illustrating the situation in-depth.
“... they’ve done a fantastic job of getting things in order ...”
-
The worker bees have been busting their tails over the last month.
All of the rock/concrete on the emergency spillway...
and a million cubic feet of debris removed from the river...
24/7 rain or shine.
Bravo to them.
That is a downstream view of the broken slab with shotcrete beneath it to mitigate further erosion.
An Oddity: A large rock has impressive (large) root complex on top of it. How these roots survived after the massive carving & pounding of this canyon is interesting. Keep in mind the distance - it is large (rock and roots). (see image in post 2444 by Repeal The 17th to see the relative size of closer workers).
I suspect the heavy rock trapped these roots underneath it following hillside vegetation erosion near the upper spillway break. For the roots to remain after the hydraulic forces + the rock debris pounding on the roots is impressive. note: I do not believe that this is a mass of rebar.
This image shows a good view of intact "Load Transfer Bars" left in the Sidewall Slab. This evidence confirms the missing design detail -of these load transfer bars- in the original construction blueprints. Discussion links 1 & 2 on FRposts below.
The size/length of these "intact load bars" answers another question on the broken junction of the sidewall slab and remaining main slab that is pulling away from the upper main spillway. An "illusion" was created by concrete remaining around the hidden load transfer bars. The remaining concrete was left attached to the left sidewall slab but this remaining concrete is not part of the sidewall slab but is part of the main slab that fractured away. Thus it created an "illusion" that the joint between the two slabs was a "beveled" type. (see third FRpost link below, circled section in post image).
These "Load Transfer Bars" confirm the "bonding force torque" link re: the downslope sliding of the failing Upper West Sidewall and the adjacent spillway slab (sliding & slight rotation). Hopefully the new drilling & subsurface repair work will have stabilized this section from further movement when the spillway is put back into use.
West Sidewall Spillway load transfer bar evidence - photo..
Missing Detail of joint between wall footing and spillway slab.
Beveled Expansion Joint (hidden Load transfer bars?)
Intact Load Transfer bars in Sidewall Slab (broken section of upper Main Spillway) + odd creature/item in canyon ("multi-legged creature in the canyon lagoon…")
A few more images have been added...
1. You can move 1 million yards of material in short order if you are willing to burn some serious diesel.
2. They got very lucky with the weather.
http://www.chicoer.com/article/NA/20170218/LOCAL1/170219704
David Little: Many have seen this dam story before
Posted: 02/18/17, 10:39 PM PST |
Evacuations began at 4 o’clock in the afternoon because of fears heavy releases from Lake Oroville would flood the city.
It was a tough call to evacuate but the state was saying there could be 10 feet of water in parts of Oroville. The city manager said playing it safe was wise. “We hope this will all be just a nightmare tomorrow but we can’t take the chance,” he said.
People evacuated, spending the night in evacuation centers. Eventually they got to go home. The city didn’t flood. They were fortunate. But people who went home were told they should not unpack and should remain ready to evacuate.
Afterward, the county complained about a lack of information and communication from the state Department of Water Resources. In Sacramento, politicians vowed to do all sorts of things. They would shore up the levees, manage water levels in the lake better, and one north state legislator vowed to get that reservoir built at Sites, which would take pressure off the system.
Sounds like last week, doesn’t it?
Wrong. It was 20 years ago.
On New Year’s Day in 1997, most of Oroville was evacuated. Some of the evacuation centers were as close as Oroville High School — residents were just told to move out of low-lying areas around the levees because the river was expected to go over them.
The weather this year, as bad as it seems, was much worse in 1997. There was a one-week period where everything was flooded.
People were being evacuated in Tehama, Hamilton City, Durham, Yuba City and Marysville. Butte Creek cut a new channel in the canyon. Highway 70 above Lake Oroville was badly damaged. No valley communities were spared. Roads, bridges and a section of railroad were washed away. It was relentless.
The inflow to Lake Oroville on New Year’s Day was 328,000 cubic-feet per second. By comparison, the peak inflow to Lake Oroville this month was 190,000 cfs.
The outflow in 1997 was 160,000 cfs. The peak last week was in the neighborhood of 110,000 cfs.
The difference, of course, is that in 1997 the spillway wasn’t broken.
Twenty years ago, the problem was high runoff. There was a concern then that the emergency spillway might be needed if the lake overflowed. It was noted in news stories at the time that the emergency spillway had never been used. It wasn’t needed.
This time around, the regular spillway broke and the emergency spillway was needed, then erosion in that ravine had dam operators concerned that the concrete wall that holds back 20 feet of lake would collapse.
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It’s good to know the levees in Oroville can handle 160,000 cfs of water. But nobody knows if they can handle a 20-foot wall of water, even if it would disperse as it flowed downstream.
Articles from this newspaper at the time show the aftermath was probably very similar to what will happen this time around — a lot of promises from politicians, some kept, many forgotten.
Gov. Pete Wilson set up one of those ballyhooed multi-agency task forces. The state tried to restrict building in flood plains, which the real estate and building industries fought. An Assembly member from Shasta County, Tom Woods, talked about a sales tax — yes, a Republican considered raising taxes — to fund levee repairs and Sites Reservoir. Of course, it didn’t happen. Rep. Wally Herger and others railed about elderberry beetles and other endangered species that slowed levee projects.
On these issues and others, some things changed, some didn’t.
The levees on the Feather River did get improved, just in time for this year’s floods. Sites Reservoir, which would have allowed Oroville and Shasta to be kept at a lower level this winter, still isn’t built. The DWR never did anything to shore up the emergency spillway, insisting all along that it was fine.
Let’s hope those multi-agency task forces and blue ribbon independent panels come up with real solutions this time.
Editor David Little’s column appears each Sunday. Contact him at 896-7793 or dlittle@chicoer.com.
I guess this "Curious Item" (Post 2447) *may* be this new DWR closeup picture. I've never seen such "snake looking" twisting of such a variety of rebar before. The closest would be the twisted rebar exposed from the crunched columns in the Oakland Cypress Street Viaduct after the 1989 Loma Prieta earthquake.
Wild.
Rebar Creature in Canyon.
Crunched columns & rebar from 1989 Loma Prieta earthquake (Oakland Cypress Street Viaduct).
That’s a lot of rebar - and it illustrates a rather violent demise of that section of the spillway! Water can be a real monster!
Of interest, the last two hours show less inflow to the Oroville reservoir than outflow, resulting in a slight reduction in water level.
http://cdec.water.ca.gov/cgi-progs/queryF?ORO
Could be where the wall rests atop the wall footing.
Standard construction practice is to place the footing first, with plenty of rebar sticking up to tie the wall securely to the footing. Then the wall forms are built around those ties after additional wall reinforcing rebar is placed.
Also, the tie rebar will need to be set off center toward the backfill face, so as to resist the overturning moment forces of the backfill.
I think I can explain the twisted ends for any interested — I know you understand it.
Usually, rebar is lapped something like 30 multiples of its diameter. This number goes up or down depending upon the thickness and placement in the design. It is tied together in that lap with annealed tie wire which has no strength after assembly. The deformations hold it from tension forces and the stressed are communicated because of development in bond of the lap.
When the initial break comes to the whole reinforced concrete member, the member bends and concrete crumbles at the break. As the forces continue to move part of the broken structural member, the crumbling continues until the bar is exposed enough to either expose laps that now separate or expose small counts of bar the the shearing of separation. These bars have become brittle from the repeated bending after the initial break in the member.
So what you end up with is bar bent to show where the member remnants were twisted in position at the time that the lap bar separated holding the broken piece in place. As the broken “wing” doesn’t break all the bar at once, the bars are twisted in different places as the wing finally separates.
And a news release - selection of Forensic Review Team for the Oroville Dam Spillway incident. Includes resumes.
http://www.water.ca.gov/news/newsreleases/2017/031517ferc.pdf
You know, I saw short drops and spikes in the water flow during my review of these tables the last month and I think they may be where smaller lakes above shut down their outflow or turn up or down a turbine.
Here's the drain pipe that was emplaced in the bedrock prior to coating a layer of shotcrete. The last photo referenced (posts 2,432 & 2,433) was at an angle where the drain pipe appeared to be truncated to the wall surface. This new shot proves the pipe has not been cut flush.
note to the curious: This piping is to allow any water- that may penetrate from within the bedrock - to drain beyond the shotcrete repair/re-inforcement. While the spillway is in operation, the water could develop a "pressurized" force via the water pushing against the shotcrete inner wall and risk compromising the shotcrete repair.
How long is is supposed to take to get that 6th turbine back on line?
Anybody know?
Well, if it had been me, I would have cut them off short to
keep the water from pounding on them, but hey, what do I know?
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