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The water was turned off on the primary, concrete spillway today so that the damage could be evaluated.

The damage so revealed is... breathtaking. With another month of rainy season to go, adding to that the melting of the large sierra snowpack yet to come, the danger from spillway failure is likely still acute:

https://www.youtube.com/watch?v=UyvDPt-HU3g

And (in this video, especially note how close to the upstream floodgates the damage has progressed):

https://www.youtube.com/watch?v=UpMkBTFxKrc

When the damage was initially discovered, it was mentioned that the original damage occurred approximately 2/3 of the way down the spillway, towards the river. This appears to be no longer the case - these new videos appear to indicate that the concrete spillway has eroded upstream towards the floodgates, to the point that now only a little more than half of the entire original spillway remains intact.

And when the floodgates are again opened (and water releases resume), as indeed they must be because there are still inflows to the lake, the concrete spillway will continue to erode towards the floodgates.

The initial damage to the concrete spillway, and that portion of the spillway itself that was originally damaged, is no longer there. The damage gone, along with a very large portion of the lower part of the spillway. There is a large canyon where this portion of the spillway used to be.

I am not sure it will be possible to effect reconstruction and repairs of this primary, concrete, spillway before the next rainy season arrives, generally in October. Construction could not start until the rainy season is over, and inflows into the lake have ceased (because the spillway would need to be shut down) - which probably means April. About six months of repair time.

The concrete spillway has eroded upstream to where the hillside is very steep, creating a dynamic waterfall from the spillway into this new canyon, undercutting the concrete under the waterfall and causing erosion to progress upstream towards the floodgates even further.

There is still an "evacuation warning" for the city of Oroville (but not for the city of Yuba City). The reason: "if something should go wrong, people need to be prepared".

Department of Water Resources Press Conference 2-27-17:

https://www.youtube.com/watch?v=OL1bb8w04Qw

This is extremely odd. If something "goes wrong" for the city of Oroville (requiring an evacuation of the city of Oroville), the exact same thing will be "going wrong" downstream for the city of Yuba City about an hour or so later.

But, so far as I can discover, there are no evacuation "advisories" or any other kind of evacuation statement for the city of Yuba City.

I live in the city of Yuba City.

Stay tuned.

Anne

Here is a slideshow of the damage from our local Sacramento television station:

http://www.kcra.com/article/10-photos-show-extensive-damage-at-oroville-spillway/8987693

As I see it, April isn't a true start date because around then or soon after snow melt will begin filling the lake again! Pretty amazing damage from kcra helicopter tonight.
Velda

I've seen it, time and again, when it comes to man vs. Nature. Nature always wins. I agree with Velda in that snow melt is going to cause a delay in repairs. That damage really is extensive. It's too bad that they can't just let the water make it's own channel, but of course it would in time undercut the dam itself, sooo........ Fingers crossed for a slow snow melt and dry weather for awhile for you.

The power of moving water.....

MandysMom wrote:As I see it, April isn't a true start date because around then or soon after snow melt will begin filling the lake again! Pretty amazing damage from kcra helicopter tonight.
Velda

Oops. Velda is 100% correct. Thanks, Velda!

The rains in our area will generally stop sometime very late March/early April. Which is about the time, more or less, that the snowmelt begins in ernest.

And, um, snowmelt from the highest passes of the Sierra often will continue until mid-June (or later) until the snowpack has completely melted. It is not unknown for snow to fall at the highest elevations in June as well!

So. . July-August-September to effect repairs. . . Three months, more or less. Hopefully, more.

I am not an engineer, and I have nothing at all to do with DWR. But looking at what remains of the concrete spillway as it stands, the hillside between the spillway and the actual dam structure has been eroding. . . towards the dam structure. That is a lot of hillside, so it is probably pretty safe. Probably. . .

But if you look closely at the slideshow (link above) there are tiny white dots above the damaged spillway in some of the photos. These are people. This gives one an idea of the massive scale of the damage. It may be that this spillway may not be able to be repaired, and that a new spillway will need to be constructed elsewhere, perhaps in the parking lot area next to the emergency/auxiliary spillway.

The cost of both, either replacement - or reconstruction and repair - will be truly astronomical.

Anybody wanna buy a nice home in Yuba City?

Anne

Photos on news today were interesting. Massive around the clock effort hauling out the mound of dirt, rock, and concrete at the foot of the damaged spillway. Currently the pile blocks the river flow which is needed for outflow from the power plant. They hope to restart the power plant by Friday but that's a lot of material to haul. Once the power plant is up, they will be letting out about 13,000 CFS of water. It's scary but interesting to see all this coverage. Another interesting tidbit was an ongoing operation to rescue fish trapped in mud puddles as river flow decreased. These are baby fish of endangered species who were born in the river and are just babies. So many different things happening.
Velda