Erosion has created a 300-foot-deep hole in the concrete spillway of Oroville Dam and state officials say it will continue grow.
State engineers on Wednesday cautiously released water from Lake Oroville's damaged spillway as the reservoir level climbed amid a soaking of rain.
Situated in the western foothills of the Sierra, Lake Oroville is the second-largest manmade reservoir in California after Shasta....
This has been a great Thread- I have been getting a completely different story from the news. When it comes to engineering topics- the news is "Fake"- or at least incompetent/clueless.
itsmoked: On your statement that these projects originally were for flood control, check this out. I recall in the 60's hearing talks by a famous engineer who had opinions on several subjects including water projects, his main specialty. Adolph J.Ackerman complained about the wishful payment plans for these projects and mentions the Feather River project as a planed major source of drinking water, not flood control. He predicted funding failures.
Here is part of a paper on this subject and a portion about Ackerman.
If you've ever been involved in anything that made the news, you know that they get pretty much 95% of everything kinda sideways with alternative facts when they rush to report on anything, a mixture of ineptitude on the topic of discussion and framing the story for the most clicks possible. I wish I didn't have the experiences that led me to know that.
But has been done in this thread is that people have looked back to earlier information, and compared various sources. This is called research, and there isn't much of it these days.
When I lived in OK the dams were for flood control, any other use was viewed as very low priority and there was enough backing to keep it that way.
In CA we have flood control, power generation, drinking water, AG irrigation, and recreation all fighting over how to operate the dams. Good luck.
We have the advantage here of looking at everything in less than real time. Moreover, as engineers, we have our STEM education that helps in the analysis, which a typical journalism graduate doesn't necessarily have, and I don't have a deadline, other than self-imposed, to process the available data.
Oroville Dam was part of the Central Valley Project, which was to control spring floods and provide a year-round water source for farming further south of the delta. As with most projects of this type, multi-functionality always sells better than single-functionality. Therefore, the ability to supply drinking water and generate electricity simply adds to the appeal of the project. The CVP plays a major role in allowing the southern half of the Central Valley to be part of the agribusiness of California.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
Regardless of the primary and secondary intents of the facility, I think we can dispel ourselves of the notion that somehow "brinkmanship" in operation (AKA playing chicken with the water levels) contributed to this disaster.
The spillway failed at a third of its rated capacity. That seems like a pretty routine operation to me.
Here is an interesting protect for the geotech engineers here. Google EARTH SEARCH the Oroville, CA area and examine the valley trends around the area, as well as look at the closeup photos of the regular spillway when dewatered. What I interpret is the bedrock there is folded "beds' probably metamorphic rock each bed with variable hardness. The direction of the discharge from the spillway failed area follows the apparent weaker rock zones leaving the failure zone. Thus, future migration of that main spillway failure erosion likely will not head for the earth dam. It also might explain "Why the failure is there?" What do you guys think? Armchair engineering, but interesting none the less.
With respect to how fast the dam filled - that's how it goes with large dams in a major rainfall event.
Back in about 2008, Gladstone (a major industrial city in central Queensland) was getting very close to running out of water - being affected by the same extended drought that impacted Brisbane and Wivenhoe Dam, 500 km to the south. The major industrial consumers had been put on notice that their allocations from Awoonga Dam would be cut drastically in a few months. I was working on some big projects to reduce water consumption (e.g. installation of dry heat exchangers to replace conventional wet cooling towers, substitution of sea water cooling in place of fresh water, etc) which were being fast-tracked - orders for major equipment and stainless steel piping were placed before civil / structural design was beyond concept layout stage in several cases.
One Friday afternoon we got a phone call from the site office that it was "pi$$ing down" (a very Australian colloquialism!) and they were heading home.
The near-empty 770 giga-litre Awoonga Dam over-topped the spillway before Monday morning, and the projects were all cancelled within a week.
azcats: per the link I posted above there is data going back to late 1999. There was a peak flow of 32K cfs in March 2011. I'm guessing that's combined flow including the flow through the power plant. Prior to that was the highest observed flow of 80K cfs in January of 2006. There were a couple of 40K cfs releases that year as well. Otherwise, combined outflow rarely exceeded 20K cfs.
If anyone can find any pre-2000 historical data that would be neat to see as well.
As someone who works on little parts I can barely pick up with my fingers and have to look at through microscopes all day long, I find the scale of these dams mind boggling. This particular statistic on the repair of the emergency spill way especially so:
"California Department of Water Resources continues to examine and repair the erosion with construction crews working around the clock, placing 1,200 tons of material on the spillway per hour using helicopters and heavy construction equipment."
1,200 tons per hour = 2,400,000 pounds per hour or ~58 million pounds per day. Where do you find 58 million pounds of rock? I suppose it's better to look at it on a volume basis, that equates to about 13,000 cubic yards per day depending on what type of rock they are using. How much can one of those helicopters lift?
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