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Old 13th Feb 2017, 01:00   #1 (permalink)
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Oroville Dam

Yet another global warming created 'problem'...

The California Department of Water Resources issued a sudden evacuation order shortly before 5 p.m. Sunday for residents near the Oroville Dam in northern California, warning that the dam’s emergency spillway would fail in the next 60 minutes.

Emergency Evacuations Ordered, Oroville Dam Spillway Near Failure


WUWT have been following it for a few days...

https://wattsupwiththat.com/2017/02/...4-feet-to-top/


Latest at WUWT...

"...The “permanent drought” in California, like the now ended “permanent drought” in Texas, is ending. But like the panic about Texas, it is rich in lessons about our difficulty clearly seeing the world — and the futility of activists exaggerating and lying about the science..."

https://wattsupwiththat.com/2017/02/...anent-drought/





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Old 13th Feb 2017, 02:49   #2 (permalink)
 
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Have you ever noticed how small children behave when you catch them in a lie ?
The same temper tantrums are exhibited by those who worship at the alter of global warming. No discussion is allowed. Verboten .


A fish swims into a wall and says "DAM"
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Old 13th Feb 2017, 19:39   #3 (permalink)
 
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Fitliker,
Than you for that very mature analysis. The world is now a better place.
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Old 13th Feb 2017, 20:30   #4 (permalink)
 
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So let us proceed beyond this.

Why is the relief channel, dump system, whatever it is called, in such a bad condition that it fails after not having been used for quite a while (assumed the drought has hit the catchment area of the dam)? Has it not been maintained properly, or has it simply not been designed to handle the amount of water it has to digest now?

A heavy downpour leading to an extraordinarily large influx of water into the reservoir is certainly catered for in planning such a dam and its associated systems, is it not? And if so, was the design fill rate (for want of a better term), and therefore the maximum planned flow rate through the relief system, exceeded in the recent weather?
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Old 13th Feb 2017, 21:09   #5 (permalink)
 
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The initial failure started in the main spillway, which had not been inspected since 2015. The inspection was off site, and "visual" (the concrete ramp was not "walked"). Starting essentially as a pothole, it degraded quickly such that the flow needed to be drastically reduced. The lake filled up, and overtopped an "emergency spillway" constructed of a surface pour of a concrete "gutter", which had no footing. The outfall was native soil, and was washed quickly downriver. Water began to penetrate the underlayment. If it fails (we're not out of the woods) thousands of people could drown as the lake gives up its top layer, fifty feet of water, all at once. People should be fired, go to prison, and the Governor should be recalled. Not likely in Caliunicornia.
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Old 13th Feb 2017, 21:21   #6 (permalink)
 
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In this video, it seems that the main overflow is not one continuous concrete structure, but rather made from, albeit large, concrete plates. A bit like a highway or an apron.

To my laymans eyes, this seems unwise, as the gaps between those individual plates can never be tight. Seeping water will loosen the plates over time, and once one of those is tipped out of its position, it may well be taken out by the stream, leading to the results shown in the same movie...

Am I wrong here? Is this state-of-the-art dam design?
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Old 13th Feb 2017, 21:50   #7 (permalink)
 
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Interested in the true story here I watched perhaps seven or eight news items describing the problem. Each explanation was different. The helicopter flew here and there, but at no time did the situation make any sense, verbally or visually. Finally this morning I saw a shot of the main spillway with a jagged gaping hole in the middle of it. Ah, now if water starts working all of that surface concrete loose, then it could all go in a bad way. Got it. Thanks
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Old 13th Feb 2017, 21:58   #8 (permalink)
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As a result of an illegal alien population estimated at almost 3 million residents. The annual expenditure of state and local tax dollars on services for that population is $25.3 billion. That total amounts to a yearly burden of about $2,370 for a household headed by a U.S. citizen.

Maybe thats why the dump or relief system was not maintained properly ?
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Old 13th Feb 2017, 22:02   #9 (permalink)
 
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Quote:
Why is the relief channel, dump system, whatever it is called, in such a bad condition that it fails after not having been used for quite a while (assumed the drought has hit the catchment area of the dam)? Has it not been maintained properly, or has it simply not been designed to handle the amount of water it has to digest now?
It's correctly termed a spillway (because it "spills" excess volumes of water flowing into the dam. A defined measure of "freeboard" is required, below the top of the earthen dam wall, to ensure floodwaters don't flow over the top and erode the earth in the wall. The spillway is designed to keep floodwaters within the defined freeboard measurement).

The spillway has possibly failed because some engineers have designed and installed a poor design of spillway that is unable to cope with the heavy erosion capabilities of a spillway carrying very large volumes of water.
The spillway is possibly too narrow - or calculations of the potential maximum volume of floodwaters have been incorrect.

Many spillways are carved out of solid rock areas near the dam, which rock can normally resist heavy erosion caused by large volumes of water being carried away.

If solid rock is not available, then the spillway is normally concrete-lined with a sizeable thickness of concrete, and a design width, that can carry away huge volumes of floodwaters without any problem.

Then you have the "lowest tenderer" problem, common with many projects. A low-ball tenderer may provide a substandard level of construction, that may have hidden weaknesses, that are not picked up until the pressure of floodwaters exposes them.
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Old 13th Feb 2017, 22:05   #10 (permalink)
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We have one of the largest (UK) reservoirs near us.

In December 2015 it overtopped - although they had been drawing down for several days,the inflow exceeded the capacity of the outflow.

Although the discharge coincided with cataclysmic rainfall across the region, the tiing of the discharge merely prolonged the downstream flooding of settlements (flood defences were overtopped) rather than being the cause of the overtopping.
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Old 13th Feb 2017, 22:36   #11 (permalink)
 
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Two Problems

1. The main spillway appears to be built over fill in the mid section. Ground movement from natural and spillway seepage left a section unsupported. Things tend to cascade from there.

As long as the upper spillway is on bedrock and /or does not become subject to retrograde erosion, it will most likely not breach.

2. The water found a path around the emergency spillway over the parking lot

Erosion around that corner would likely be catastrophic
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Old 13th Feb 2017, 22:53   #12 (permalink)
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I participated in the construction of an 'earth dam' for a reservoir.

The valley was closed off by constructing a 110ft high dam from clay which was compacted layer by layer (my task was to test samples for shear strength after it had been compacted).
The clay core was edged with sandy earth and then covered with stone facings so that the water did not erode the structure.

There was no rock within the dam wall structure (apart from the stone facing). The clay was found further upstream (at the head of the reservoir) and 'borrowed' by scrapers before being transported to the dam location and laid. Subsequent passes of laden scrapers effected the compaction.

With regards to filling, the rate of inflow was underestimated, and once the concrete 'plug' had been cast to start the fill, the level rose faster than anticipated and the final stone blocks were placed by workers wearing wellingtons.
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Old 14th Feb 2017, 00:42   #13 (permalink)
 
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Onetrack sums it up pretty well. It's clear that the sheeting on the spillway has failed. There could be several causes, including poor design, construction not in accordance with the design, under-estimation of the design flood or incorrect operation so that spillway flows exceeded the design capacity.

I've seen one other spillway have a similar sheeting failure, but in that case, it was possible to operate the spillway gates so that the damage didn't propagate.
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Old 14th Feb 2017, 01:57   #14 (permalink)
 
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Engineer on news tonight, says the concrete bits are safe despite there being some minor damage, it's the earthen part that's in danger. As I'm not an engineer, I'll take his word for it.
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Old 14th Feb 2017, 02:07   #15 (permalink)
 
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People should be fired, go to prison, and the Governor should be recalled. Not likely in Caliunicornia.
Since ever when did Politicians and Government Workers take it in the Neck for malfeasance or misfeasance....ever?

In that matter....California has no monopoly on the lack of adverse action against those guilty of such conduct!
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Old 14th Feb 2017, 02:14   #16 (permalink)
 
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Westie,

The flow will disburse before Oceanside, not to worry.

GF
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Old 14th Feb 2017, 03:50   #17 (permalink)
 
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Hope so, I passed on flood insurance.
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Old 14th Feb 2017, 15:27   #18 (permalink)
 
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SAS,

"In that matter....California has no monopoly on the lack of adverse action against those guilty of such conduct!"

Noted. However, California is currently under virtually hard left political sway. We are also extremely polarized. Though Sacramento is eighty percent Democrat, the State as a whole is roughly fifty fifty, the difference being the Democrats are far better at stealing taxes and using the ill gotten gains to reelect themselves, perpetually.

One major f up away from civil unrest. Cali looks Democrat, but the rest of us are pretty pissed off.....
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Old 14th Feb 2017, 15:28   #19 (permalink)
 
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Where I live, our house is judged to be in a flood risk area due to the proximity of the Calavon river, and we are required to have flood insurance. At an altitude of 150ft above the river the requirement is clearly bonkers, but because someone drew a line on a map decades ago we have to comply. French bureaucracy, eh !
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Old 14th Feb 2017, 15:39   #20 (permalink)
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Some years ago, the Environment Agency published an on-line 'extreme flood' map.
As I live in an area which is subject to river flooding, I studied the map.
I spoke to the EA 'flood manager' and told him that, if their map was accurate, the water would be flowing down my chimney (and as my house was a three-storey house that had never been flooded in 275 years, that would be 'unusual'.
He confessed that they had simply drawn a line parallel to the river.

The current extreme flood map, produced with historical data provided by me, represents reality and this was reflected in the recent '150 year event' that we experienced in December 2015.
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