[KaiserJeep]

The Oroville Dam is for water supply, hydropower, and flood control. I have hated it since before I moved here, in the late 1960's it destroyed one of the state's most extensive steelhead fisheries just by being built. They try to pretend by releasing millions of hatchery fish below the dam, but they are clones with little diversity and offer poor sport.

I could stand not having the dam. I could stand not having California be the vegetable supplier of the USA. I could stand seeing Dimmycrats dangling in nooses in Sacramento, especially when they are like Moonbeam.

What discourages most, is the apathy of the sheeple to rank Dimmycrat incompetence.

[hvacman]

How a spillway is SUPPOSED to work:

http://www.redding.com/story/news/local ... /98270214/

They didn't HAVE to use the "emergency" gates, but thought it a good idea to test them. Note that they do test them every 10-20 years, when "opportunities" like this come up.

Oroville never "tested" their emergency spillway. It received its first "test" when it HAD to work when the main spillway blew out. Test result - failure. oops.

[Plantagenet]

$this->bbcode_second_pass_quote('pstarr', 'I')t's fun throwing around partisan blame at the Moombeam, California et.al. but isn't the problem simply an infrastructure one? The Oroville spillway is a 60-year old cement slab on grade that settled. That kind of thing. Planty, these problems are truly not Obama's fault.

[KaiserJeep]

The situation at Oroville dam is very different from San Jose and the Anderson dam.

Oroville is a state dam with a hydro power penstock and a separate main spillway and an emergency spillway. It needs to be attended and operated and inspected and maintained. The budget for this is at the state level, and Lake Oroville is the primary source of irrigation water for California's Central Valley, along with Lake Shasta.

Anderson is a Santa Clara County dam, it has only one spillway and no floodgates, it simply overflows when full. Aside from the fixed and non-operable spillway, it has a 24" diameter pipe used to provide water, or to discard water to keep the lake less than 100% full. When a study showed that it was vulnerable to a medium earthquake on the Calaveras Fault, the level was reduced and the seismic improvements begun, scheduled to finish after 20 years in 2018. It is tiny, about 2.5% the capacity of Oroville, but still by far the biggest reservoir near Silicon Valley.

Anderson will overflow whenever the rain on that part of the valley exceeds the 24" outlet pipe capacity. It is working as designed to work, and was darned near to being upgraded to withstand earthquakes without failures. The flood zone around Coyote Creek has been there forever, Anderson dam reduces the frequency of floods, but was never designed to eliminate flooding.

The thing nobody on the news is telling you is that the flooded areas are almost exclusively low income minority neighborhoods. The first day of the flood was an area called "Little Vietnam", with largely Hmong and Vietnamese and Cambodian inhabitants. The four trailer parks that flooded the second day were largely occupied by elderly people that were of Hispanic, Asian, and Polynesian origins. None of the pricey and toney neighborhoods were built in flood zones. Heck, even the golf courses along Coyote Creek are on high ground and were open today, when the sun shone all day.

[onlooker]

https://www.nytimes.com/interactive/201 ... p=cur&_r=2
America’s Aging Dams Are in Need of Repair

[hvacman]

with the lake drained down to about 840 feet, the DWR has shut off the main spillway gates to give them a few days to attempt to remove the 250,000 cubic yards of concrete, dirt, and rock that washed out and filled up the river channel. This debris created a small dam that backed up water to the base of the dam and prevented the hydro plant from operating - shutting off an 18,000 cfs outlet that the lake desparately needs.

The link below has a brief video that shows the current condition of the main spillway. To get a perspective of the magnitude of the damage to the spillway and the enormous effort that will be required to repair the spillway by next winter, note that the spillway is about 200 feet wide and the concrete base that looks like paper is about 18" thick. A little bondo and tape won't do the job.

https://youtu.be/UyvDPt-HU3g

It is very likely that it will take years to bring Oroville back to full operation (as in allowing it to completely fill up with water). The engineers first have to figure out what failed on the spillway, then how to fix it, then actually fix it. It might be that there is something fundamental (poor design, flawed concrete material, etc.) that would require the entire 3000+foot long spillway to be removed and re-constructed. They also learned that their backup plan of the emergency spillway was not a viable plan, as the almost-disaster revealed. That means fundamentally rethinking the entire emergency spillway design, from the top of the lip down to the river channel. Perhaps they need some gates. Definitely they will have to install a real concrete path all the way to the river - essentially another concrete spillway of equal capacity as the existing.

All of this takes time and money - a lot of both. There will be finger pointing and lawsuits aplenty. And the winter rains of 2017-2018 will start again in just 7-8 months. IMHO, based on how the wheels of government turn, Oroville will not be "fixed" for several years.

This very-wet winter has broken California's second-largest reservoir. Those who depend on it for their summer water may wish that the drought had continued a little longer.

[dohboi]

In the discussion of the emergency spillway, some were wondering what the nature of the bedrock was. Does the erosion under the demolished section of the main spillway suggest anything to you about that issue.

It looks to me as if some of the 'bedrock' is fragmented enough that it did indeed get eroded by that volume of water. But maybe I'm misinterpreting what I'm seeing. If that is the case, though, does it imply that using the emergency spillway again would be even more dangerous than some thought.

[Cog]

Looks like a metamorphic rock. Some sort of schist. Its not particularly consolidated by the looks of it. Lot of fractures along and through the bedding planes. Its been a long time since my undergrad days in geology but I seem to remember it being a sort of crappy sort of rock that crumbles. Maybe our resident geologists can weigh in on this. Which sort of makes sense if you have ever encountered its sedimentary predecessor shale.

Here is a science paper on the geology of the Oroville Quadrangle.

https://archive.org/stream/geologyoforo ... h_djvu.txt

"Bedrock Series"

Unnamed Metavolcanic Rocks

Two separate belts of dark-colored, massive to
schistose, amphibole-bearing metamorphicphic rocks, be-
lieved to have originated as basic to intermediate vol-
canic rocks, were mapped. On the basis of stratigraphic
relations and degree of metamorphism, it is considered
probable that they represent the oldest rocks in the
area. The rocks of the two belts may be equivalent
to one another, but because of dissimilarities between
them, they are discussed separately.

[dohboi]

Thanks, Cog. That was my impression, too. But of course I didn't have the proper terminology for it.

[hvacman]

I don't know anything about the specifics of the rock under Oroville's main spillway, but it sure eroded away in a hurry, with 100,000 cfs blowing through it. See before and after photos below. You can see the debris in the river bed below it. There really isn't much good "Bedrock" under most of the valley and lower foothills of the Sierras. Most of this stuff is the remains of former inland seas. You have to get up pretty high before you get to where the granite is.

The emergency spillway never had more than 12,000 cfs flowing over it. If this is the same stuff that is under the dirt at the top of the emergency spillway, the damage that would have happened if they ever actually did have the "design" emergency overflow of 150,000 cfs, without even any concrete to protect it, would have eaten up the mountain and taken out footings under the lip - no wonder DWR engineers feared an eminent catastrophic failure.

[hvacman]

oops...forgot to attach photos.

[vtsnowedin]

That is going to be a nice fat construction project for the area concrete contractors to bid on.

[Cog]

$this->bbcode_second_pass_quote('vtsnowedin', 'T')hat is going to be a nice fat construction project for the area concrete contractors to bid on.

[dohboi]

I had heard hundreds of millions, but now I'm thinking billions!

[hvacman]

$this->bbcode_second_pass_quote('Cog', '')$this->bbcode_second_pass_quote('vtsnowedin', 'T')hat is going to be a nice fat construction project for the area concrete contractors to bid on.

[Cog]

If this were not an emergency situation you could probably spend $50 million or so. But the time constraints drive the cost way up. I'm going to take a wild stab here and say about $500 million or so to get the emergency dam armored up, dredging the primary river channel clear, and repair the regular spillway. That is working 24/7 from now until job completion.

The power plant is only capable of discharging 12.5K cfs. That is not enough discharge to prevent the dam lake from filling up again. You can't discharge through the regular spillway while its under construction obviously, so you are stuck with the emergency spillway.

[dohboi]

Whether it's hundreds of millions or billions, I can't help wondering how much wind or solar could have been built with those funds.

(And yes, I know this is as much if not more a dam for water management as for electric generation...it just doesn't seem to be doing a great job of managing water flow right now...just sayin'...)

[vtsnowedin]

People are just throwing big numbers out there to get the funds coming down the pipeline. One story says 200 million but I don't see that in the pictures even if they demo all the original spillway and start over. Another story says the hole is 250 feet wide and 45 feet deep with no mention of width. But say they have 250 by 250 by 45 of hole to fill. That would come to 100,000 cubic yards and at $200/CY would cost 20 million$. Of course there will be some Fam Dancy enguneerin that will cost heap much.