Two small Earthquakes were recorded near Lake Oroville in the last 24 hrs, which appear to be a result of the fast lake level changes, and the subsequent release of pressure from water weight. Note the two yellow dots on the USGS map below:
Source of map, here
JD Elam notes on Facebook:
The predicted earthquakes due to extreme lake level change have started. 2 in the last hour.Ā 300,000,000 pounds of water has been removed in two days, that will cause the earth to jiggle a bit. These were predicted and should not cause any problems.
The magnitude of the quakes were very small, 0.8 and 1.0 on the Richter Scale, and there does not appear to be any threat to the dam infrastructure.
As they say, when it rains it shakes.
0.8 I believe that’s equivalent to dropping a bowling ball.
That’s okay, unless you drop it on your foot.
It was Lena Dunham sliding over the spillway
Let her eat cake.
Oh wait, she already finished it.
Kinda like a burrito byproduct while standing next to the seismometer
DITTO KERRY!!!!!
How many quakes of that magnitude would be felt in that area in a normal week or month?
100s
Sorry MarkW. You did say “felt”. A 1.0 is seldom, if ever, “felt” and quite often not “recorded” by normally positioned equipment. It may be sensed by that equipment, but as there are millions per year worldwide…. But they may have equipment in place permanently (when they built the damn) to measure (and record) very local movement, if not they probably place some strategically around the damn to sense movement specifically during the current situation.
I believe that the threshold for disturbing the vestibular structure of the human ear is about 4.0; nothing below that will be “felt” by humans.
OMG!!! Are they fracking near the dam????? We’re all doomed!!
Harry,
It’s already fracked up…
If I remember correctly M1 earthquake energy release is about 1.75 TNT.
For the rest of the scale multiply that by 32, so M2 = 56 TNT (btw there are more than one million M2/annum worldwide).
Top of the scale M10 calculates to 10^12 * M2.
(I stand to be corrected if anyone has more accurate numbers)
1.75 what? Pounds, grams, kilograms?
Hi Mark.
My wrong. In kilograms (kg).
M1 magnitude earthquake energy release = 1.75 kg TNT
Is there a reference distance? “1.75kg of TNT at (x) meters distance (y) meters below ground, said ground with a composition of (a,b,c) etc”?
Hi there
1.75kg of TNT blast at the hypocentre (focus) of the earthquake.
You would be hard pressed to even feel a 0.8 earthquake.
Very hard pressed. This is the MMI curve for California crust for a Mag 1.0. Below MMI-II, you probably will not even notice it.
http://oi65.tinypic.com/jjy3p0.jpg
They no longer appear on the USGS map. They fall below the 2.5 threshold, so you have to modify the settings, but even that won’t bring them back.
Go to the ‘historical earthquakes’ page for that area on the USGS site and specify >3.0. It’ll show several (half dozen plus or minus a couple.) a year for many years.
And there isn’t a chorus of climastrologists and lame stream media fan boys claiming this all because of gullible warming yet?
Ha-ha! I hope you don’t mind if I use “climastrologist” and “gullible warming”!
Global Warming, or Nobel Gore Bling?
It almost seems that, with a new sheriff in town at EPA, and the executive orders pouring out WRT pipelines and carbon regs, the usual sources for all the “… because climate change!” are shrugging and saying “Why bother?” Silence is golden.
When I saw the name, JD Elam, I thought of Jack Elam the actor who co-starred with James Garner in the movies: “Support your local Sheriff” and “Support your local Gunfighter”.
Your comment caused that thought to break out in a smile. Jack Elam could smile a genuinely crooked smirk.
Of course it’s not gullible warming!! It’s all Trump’s fault… Hey, I know, where those earthquakes are happening, maybe we should name the fault line “Trump’s Fault”… š
SWARM OF EARTHQUAKES NEW THREAT TO OROVILLE DAM!!!
/sarc
Nit Pic … Richter Scale is no longer used .. it has not been used for a long time. Moment magnitude is the current earthquake intensity scale used .. or just “Magnitude”.
Correct the site displays the values as M1.0 and M0.8
Correct. And the Richter Scale was devised for a very specific seismometer, the Wood-Anderson. And interestingly, the Wood-Anderson clipped above a moment magnitude of about 6, so to talk about, say, a magnitude 8 on the Richter Scale makes multiple errors.
“300,000,000 pounds of water has been removed in two days”
An acre foot of water weighs about 2,719,000 pounds (325,851 gal/AF times 8.34 pounds/gal of water). I have seen estimates of at least an acre foot/sec. So # of seconds in 1 day = 24 hr/d times 60 min/hr times 60 sec/min = 86,400 sec/24 hours. So I calculate over 234 billion pounds/24 hours, if my math is not wrong.
Somewhere Robin Williams is smiling about a big dyke protecting this thing …
Actually she’s cracking up under the strain…
Is there a little Dutch boy in the house?
What’s relevant is the change in water depth behind the dam and the speed of change, not the rate of change in volume extracted. What is the plan area of the reservoir water behind the dam? Just dropping the water to the spillway channel inlet out of the dam would involve only a few metres depth change at most. What is the design’s emergency drawdown rate?
Typo! I meant … channel invert (level)
How did you ever land a man on the right moon working with such complicated units of measurement?
They did all their calculations with slide rules š
Working in traditional units requires a substantially higher level of intelligence than working in SI units, and that’s why we got to the Moon and no SI-using country did.
Well for one thing, most Imperial units can be divided by 3 without having to truncate any asymptotes. š
Ah, Timo beat me to it. š
Neil
Metric
300,000,000 lbs = 136,077,711 Kg = 136,077,711 litres
Divided by 2 = 68,038,855kg/per day = 1,133,980 per hour
divide this by the surface area and you have a better idea of the weight impact.
One of the advantages of metric is that 1 litre = 1kg
Ozonebust February 16, 2017 at 12:32 pm
One of the advantages of metric is that 1 litre = 1kg
one disadvantage is believing it.
Weight of water vs milk. Weight of water that drains across different mineral deposits.
While in a liter or Gal. the difference is small enough to ignore, but once you get into the million weight numbers it can become a problem.
mchael
Mike
I will bear that in mind when ordering a large mineral water
1 litre of water equals one kilogram. Now try dividing that by three.
300,000,000 lbs of water in 2 days? Do the maths: that’s roughly a 50 metre cube of water – hardly earth-shattering or earth-quaking for such a massive volume behind the dam!
More’s gone in than came out. The last rain storm added 750,000 acre feet, more than has flowed out.
Must I point out that the earthquake was caused by global warming ! Where are my fellow trolls when you need them ?
Sarc
I was in discussion with someone some years ago now who believed aCO2 driven climate change was responsible for an earth quake swarm in Wellington, New Zealand.
300,000,000 lbs of water is about 135,000 cubic meters, not 50.
Oh, I get it. A cube that is 50 meters high.
I find it curious that one of the mini-quakes is just above the emergency spillway and the other is along the flow path from the emergency spillway below … strange coincidence?
The old diversion tunnels created when building the dam waking up? One of them had some serious repair in 2015.
I was wondering if it was possible to reactivate those old diversion tunnels? Or were they filled with concrete?
There were earthquakes after the dam was built and filled. Check it out.
On Aug. 1, 1975, there was a magnitude 5.7 quake near the dam on the north-trending Cleveland Hills fault, part of the Foothills fault system.
This can happen when reservoirs initially fill up over previously dry land, and the water finds its way into small faults and lubricate them to the point of minor slippage.
10 on the Richter scale should not be called an “earthquake”.
We need another word. Like “tremor” or “ground whimper”.
I know that technically 1.0 and 8.0 are both earthquakes but it’s misleading.
“There’s a cat in the garden,” is true if the cat is a tabby or a tiger.
But it pays to know the difference.
“10 on the Richter scale should not be called an āearthquakeā.”
ātremorā or āground whimperā seems a bit soft for a 10, no?
Check out this link. There was a 5.8 quake at the Orville Dam in the 1970’s. The second largest induced earthquake in recorded history in the USA.
http://temblor.net/earthquake-insights/oroville-dam-is-also-at-seismic-risk-2538/
Missing decimal, I believe. Or comma, for Europeans.
Correct. Missing decimal.
I meant 1.0.
Has there ever been a 10?
9.5 in Chile largest measured. Alaska 1964 was 9.2.
Salvatore
“The scientists said that the weight of the water actually clamps the fault tight” – dont you love it.
M Courtney February 16, 2017 at 12:12 pm
Has there ever been a 10?
not in our history. Thankfully.
Fault size, length seems to be one of the controlling factors.
Best advice, do not live near long deep fault lines.
michael
IIRC The old Richter Scale went up to 12. At that theoretical magnitude, buildings would be launched into the air and the ground would move up and down in waves.
“drednicolson February 17, 2017 at 8:09 am
…and the ground would move up and down in waves.”
That already happens at lower magnitudes, P and S waves. During an earth quake you can feel it. Largest quake I experienced in New Zealand was about a 6.5 and being thrown from bed. Very interesting experience.
quick question: do any of you REALLY believe what the govt is telling you?
Short answer: No. Long answer: Heck no.
At 100,000 cfs enough water will have been released in 40 hours to supply all of LA for a month. In 20 days it would be enough for an entire year.
So much water is being released that California actually needs. Really unfortunate.
There is still a “mess” of water in them thar hills… the southern reservoirs should be filled up by this run-off; that is L.A.’s problem.
They could have watered every lawn in Beverely HIlls with that much water. Most unfair.
Well there’s nowhere to put it so they have to let it go.
That’s exactly the problem – California doesn’t have enough places to store water.
Poor little California Delta Smelt – all washed out to sea.
It would be interesting to see the repair work they have managed to do in the past few days. I hear they have been working hard but don’t seem to find any visual coverage of the results.
I have been looking for spillway(s) repair results lately, and no results yet…
There is a long story and many pictures and video on the Daily Mail.
Is it any wonder that thing fell down, what an utter and total hash of units being used, acres, ponds, feet, cubic feet per second.
The more you .look, it was pretty damn lucky you actually hit the bleedin moon in 1969 – don’t tell me, you were actually aiming for Jupiter and just spun it to make it look like a ‘Moon Landing Success’
Lucky you hit anything!
Lets try:
An acre foot is about 1200 tonnes of water.
If the dam is releasing 100,000 cubic feet per second, that’s about 3000 tonnes per second
Maybe now, seeing 3000 tons of sh1t *per second* hitting that poxy slab, we can appreciate why it crumbled.
If 1000 millimetres of rain falls on one square kilometre, that is 1 million tonnes and to a first approximation, that is 250 acres and 39 inches deep
It makes it now easy to see how Karl disappeared The Pause, turbulence in the intake ;pipes of the ships warms the water – exactly as Joule did his experiments.
So, we’ve got 3000 tonnes= 3 million kg falling what? – 200 metres out of that dam.
Energy= mgh = 3e6*10*200 = 6e9 Joules (per second) or 6 gigaWatts or just over 8 million horsepower for petrol-heads.
No matter, 4200 Joules will warm 1 kg by 1degC, so the water at the bottom is just less than 0.5 degC warmer than at the top.
Holy H Kow, I’ve just found the missing heat!!!! and the metric system means I didn’t need a supercomputer to work it.
(please recognise the tongue in cheek here, I do luv you all dearly, even Griff, mwaaaaah) and not a single polar bear lost even a single whisker in all that)
Their spelling of English and its pronunciation are also appalling, and they drive on the wrong side of the road.
could this be expressed in football-field cubits please , that would make it much easier for common people to understand. I just how many Olympic swimming pools is that ?? I’m lost. š
And all that energy which is pounding the spillway, how many Hiroshimas is that?
Almost 7.
Furlongs per fortnight.
I prefer the hand-stone-fortnight system – you can put the decimal anywhere you want and nobody can figure out for sure whether you’re right or wrong.
Peta from Cumbria, now Newark February 16, 2017 at 11:46 am
Actually we didn’t start crash spacecraft into Mars until NASA went metric. Russia/USSR always used metric and were piledriving things into Mars from day one.
michael š
Touche’, mon ami!
Or the earthquakes could be due to Global Warming through the Caterpillar Effect. (or maybe not)
California is always having earthquakes
Califormia is always having droughts, they’re never happy.
I think (don’t know for sure) that these small earthquakes are just a coincidence…it’s California…
Well not always. Sometimes their menu includes downpours with a side of mudslides followed by a failing dam for desert. Oops, I dropped an ‘s’ but it still works in a punny sort of way.
Wildfires followed by mudslides the next time it rains.
Almost as if old M.Nature is trying to tell them: “Stop building big expensive houses on mountainsides and fault lines, you retards!”
A bit of a quiet day in California. This is the last 24 hours, …http://earthquake.usgs.gov/earthquakes/map/#%7B%22autoUpdate%22%3A%5B%22autoUpdate%22%5D%2C%22basemap%22%3A%22satellite%22%2C%22feed%22%3A%221day_all%22%2C%22listFormat%22%3A%22default%22%2C%22mapposition%22%3A%5B%5B31.50362930577303%2C-127.99072265624999%5D%2C%5B42.42345651793833%2C-109.9951171875%5D%5D%2C%22overlays%22%3A%5B%22plates%22%5D%2C%22restrictListToMap%22%3Anull%2C%22search%22%3Anull%2C%22sort%22%3A%22newest%22%2C%22timezone%22%3A%22utc%22%2C%22viewModes%22%3A%5B%22map%22%2C%22list%22%5D%2C%22timeZone%22%3A%22local%22%2C%22event%22%3Anull%7D
With all the fake news out there especially with CNN ( certainly not news), I would stay away from there until this last storm passes as a precaution !
Bravo Sarah! Certainly Not News…spot on!
Just spit-balling a few potential alarmist headlines:
Man made structure and actions triggering earthquakes.
Gia fights back.
Nature cracks under human meddling.
Rapid drawdowns often destabilize reservoirs banks because the water in the soil cannot drain out fast enough and there is no supporting water pressure from the reservoir. A large enough collapse could itself create a displacement wave that would overtop the dam. This actually happened in France some years ago. That dam was a concrete arch and survived. Earthen dams do not survive overtopping.
Sorry for repeating myself but…
Emergency spillways are not ādesignedā for use. They are a designed weakness in the structure to create a designed failure mode and path. Think of a frost plug for analogue.
A earthen gravity dam WILL fail if overtopped. To avoid using such language the weakest or lowest point is given the name āemergencyā spillway. When the dam overtops, the dam HAS failed. The overflow undercuts at the desired point and the reservoir drains. That is how it is āsupposedā to work. It is the design feature.
The E- spill doesnāt do much for the people downstream but it DOES save the majority of the main dam and powerhouse. No small achievement ā mucho $$$ GK
GK, I think your theory has some holes in it. 1) What would be the value of a collapsing feature that isn’t under control, but just happens at the whim of a storm? It wouldn’t be hard to design in a real “fuse” that would be under the engineers’ control; a spot that could be dynamited. To have a random collapsing feature with 100K’s of people living downstream would be Dam Stupid. 2) The federal guidelines specifiy that the emer spillway’s drainage route can suffer significant damage if used and still be acceptable. That’s damage, as in trees washed out and the hillside gets some gullies, not a collapse.
Another thing that makes me suspect the accuracy of your statements is the certitude with with you express them.
Woody, I understand your skepticism considering all the misinformation outputted. Public releases are not useful to an Engineer. A designed failure mode is part of dam construction and the E-spill is that design. To suggest that a total dam failure is preferable to a partial failure would be bad engineering.
I will admit the language I am using is blunt, but it is the truth. The e-spill is merely a plug for the reservoir and designed to fail (by eroding [failing] the plug) before the main dam fails.
And, yes my main engineering experience is nuclear, but I have some with hydraulic (dams) and thermal experience also. Dam construction, is basic, at it’s core. GK
Pressure cookers have those little plugs, which blow when reaching a certain high pressure so that the entire pressure cooker doesn’t blow up in your face.
Exactly. This is a film of such a ‘made-to-fail’ plug failing; it allowed a ‘controlled’ release of water.
Here tis…
https://dailytimewaster.blogspot.com.es/2017/02/breach-of-auburn-coffer-dam-in-1986.html
Finally, someone gets it. Thx for the excellent video. Hope everyone watches and cleans up the misinformation. GK
With the principal spillway designed for a 100 year Return interval event, and the emergency spillway designed for a half PMP or PMP event, Use of the emergency spillway cannot be called a failure.
Uh-oh.
Maybe the little quakes are timed when the work crews are up top dropping large
boulders and bags of rocks from a height that is enough to make the ground
move a little. They are dropping with helicopters and large dump
trucks. Whenever a large enough truck loaded down goes by at speed, I can feel
the earth shake a bit. I sure hope that dam holds long enough to allow
California to get out of the way! Iām beginning to think that large hydro
projects store too much energy to be safe, no matter who controls them.
Latest reported news is they have reduced the flows over the primary spillway to drop the downstream river levels sufficiently so they can clear snags and debris from the outflow areas below the turbines. The chunks of concrete from the primary spill way are ‘damming’ the outflow stream from the turbines. They very much want to get the turbines running again, both for the electrical generation as well as adding that flow volume to the total available via the spillways, in readiness for the next deluge that looks to arrive there Mon – Tues. The generators add about 13,000 cubic feet/sec (CFS) to the overall flow rates. In the mean time, they are still releasing about 80,000 CFS and the lake levels continue to drop, albeit more slowly. Reservoir water height was 867 ft at noon today.
http://www.sacbee.com/news/state/california/water-and-drought/article133078564.html
Those levels are strange.
\When they were already at draining at 100.000 cfs, they were equating that to between 3 and 4 inches per hour in level reduction.
At 4″/h, that’s 8ft/day.
At 11am on 2/15 level was 878. 25h later it was 867.
How do you drain 11ft when it should only be about 8.3ft in that time frame?
Yes, also mentioned was 1ft/2.5h, = 4.8″ per hour
That still only equals about -10ft.
Total reduction:
901 -867 = 34ft.
Not counting the hours on Sunday, that makes 3.5 days of drainage, or 10ft/day.
That would confirm the 4.8″…
Still strange IMO.
As to GK comment:
That overtopping = failure is correct, but that’s WHY an emergency area is provided that prevents the BULK of the dam from being overtopped, by allowing a small PORTION of it to be overtopped at a somwwhat lower level.
That portion is SUPPOSED to be strong enough not to suffer from the problems of overtopping at the main parts of the dam.
Obviously this failed, if that meant-to-be-overtopped section had erosion damage so quickly, and couldn’t even withstand a rel. modes flow of 13,00cfs for more than a very shot time.
12 years ago, 4 envirnmentals DID petition for a reinforcement of that emergency flow-path, but the government (typically) claimed that wasn’tt necessary at all.
Obviously again they were wrong, and these groups were actually right for once.
Surely that had good data and evidence to make this claim, so at least it must have been reasonable.
More serious is the general design issue:
The spillway was only designed to allow 150,000cfs of drainage.
Yet the highest ever level of inflow into the lake was 250,000cfs.
Some failsafe method:
For the worst case scenario (a close to full dam with a WHITE swan inflow rate) to rely upon the emergency spill-way to drain 100,000cfs is ridiculous, and so typcial of engineering in the US in general.
Remember the New Orleans levees?
Their design maximum was at something like 20-25% of what the Dutch do for their North Sea dams.
Even the dams along the lower Rhine, for ex. in Cologne have higher strength than New Orleans ever did, and these can’t be affected by any storm surge.
But hey, screw the people…
Finally a question for those here who know the dam better than I:
The main spillway drains down the hill on the left of the dam, and hits it relatively high up.
How far below the top does it actually drain?
Is there no drainage from much further down, other than the 13,000cfs provided by the power station?
That doesn’t seem very smart, if for what ever reason, a level reduction by hundreds of feet were ever needed….
Remember that surface area increases as the depth increases. Therefore a rate that produces 4 inch per hour reduction at one depth will produce a greater rate of decline at a shallower depth. There should be a depth volume curve available somewhere that would show you the volume stored at each depth.
Moderator
I prepared a reply to this comment but word press will not allow my reply to post for some unknown reason. I may have flagged some sort of security action. My reply comment has been blocked since yesterday’s above comment. Could you check your end for a more mundane possibility. It seems to hang just on the dam related topic. GK
[it simply got flagged by the spam filter due to word combinations – you made over a dozen identical comments, and all got flagged. The most recent one is now posted, and the duplicates deleted. -mod]
Too many questions for me to tackle, but I will try to clarify the e-spill aspect.
The Beauty of the E-Spill\Plug system:
E-spill is a passive system – it requires no gates, pumps, strainers, power or human intervention or initiation to operate.
E-spill operation is reactive to dynamics – the greater the overflow, the faster the plug erodes (hours to days). The time from e-spill overtopping to plug erosion is dependent on the volume rate. THERE IS NO MAXIMUM E-SPILL FLOW RATE. All talk of e-spill max flow rates are a distraction. Undercutting destroys the dam horizontally until level drops and it achieves any flow rate it damn well needs.
E-spill cannot misfire – Water overtopping the e-spill will ONLY occur if ALL CONTROL over level is lost. The dam will fail, but in a dozen different ways. E-spill guarantees the dam will fail in one specific designed way… period.
Not over sensitive – the e-spill is hardened to tolerate small flows for short times for accidents or other brief excursions. Care is needed when re-enforcing as you cannot defeat the prime purpose. At last weeks overtopping rate 80-100 hrs seemed like the plug failure rate (they ran about 40 hrs and it was about half way through) Some capability has been restored by recent re-enforcement.
E-spill fails the dam – saves the main dam and powerhouse… nothing else survives especially downstream. However the e-spill is for equipment/infrastructure protection mainly… investment NOT people. It DOSE give extra time for evacuation but evacuation should be complete BEFORE overtopping occurs. Why this didn’t happen is unknown to me.
The big negative is that even a designed failure is still a huge disaster. The authorities do not want the public to know any of this and are the main source of misinformation. Someone else with actual numbers will have to field the rest of your questions. I have nothing more to say. GK
jdp…The dam will be doing good to withstand earthquakes and rain . whats left ,meteors,hail, lava, wind,, must watch the water table to see if earthquakes did not cause a rupture.
jdp…If by tomorrow the Reservoir water height level is down to 550 ft, then look for a rupture.
jdp…A good chance of more earthquakes.
There is a rock quarry in the immediate area. Blasting perhaps? A magnitude 2.3 on the 8th; the same day as the concrete spillway flume damage began. A shock induced crack that rapidly opened up? A strange coincidence.
Go to USGS here. Click “Interactive Map”, select Satellite top right and zoom in. What time did the breach in the spillway appear?
If the quake is generated by blasting, then the USGS map states that on their daily map.
According to this the breach was discovered on Tuesday the 7th. The day before.
Native American lore states that massive rain caused by Gods Crying. Is California doing something to upset the Gods? Also Earthquakes are God’s way of shaking us awake for bad behavior. Any issues in California upsetting the God’s?
It’s the wrath of God punishing the State because we voted for Hillary instead of Trump.
Does anyone know if they filed the proper environmental impact statements? I think they are leaving themselves open for years of lawsuits.
If it is the dam construction you are referring to, there was not an EIS process when it was designed in the 1950’s and built in the 1960’s. That process did not begin until the 1970’s.
I’m pretty sure Mike is talking about the coming floods.
I’m going with Mothra.
You can’t go with Mothra, those two little fairies have already taken the available seats.
maybe California wont have to leave the USA after all..just break off from the continent
Yeah – continental drift. California continues going Left!
The predicted earthquakes due to extreme lake level change have started. 2 in the last hour. 300,000,000 pounds of water has been removed in two days, that will cause the earth to jiggle a bit. These were predicted and should not cause any problems.”
And if your wrong and people die? WHO GOES TO THE GAS CHAMBER????????
Those who said that California was soon to be all dessert.
Yeah, or the dam is shifting from undercutting.
Filling a discreet basin inert days with megatons of water (specific weight 1, but sheer mass does it)
must have Effects on geology in the blink of an eye.
Tell me.
Would water, resulting from the heavy rain after years of drought plus the high pressure dammed water, seeping down cause movement and lubrication in fault stresses thus increasing chances of stress relief?.
Massive quakes like that would send the anti-frakking community into a tail spin!
G. Karst,
The logic here escapes me.
you keep saying that the e-spillway is designed to fail.
That is not true.
It is designed to be overtopped before the rest of the dam gets overtopped.
Hence the lower level of the lip at that e-spill point as compared to the rest of the dam.
Why would the failure of this section of the dam actually ever be necessary, let alone desirable? If constructed in a way to really reflected the ultimate worst-case scenario, it could would fulfill its funtion of maintaining a level of about 901 or so feet, period.
It is certainly possible to design that emergency pathway in such a way, i.e. permit continuous drainage at that section without the undercutting erosion just seen.
That could include extending the e-spillway wall much farther down in the hillside (which would allow more surface erosion without undercutting problems, or by doing what the petition from 12 years ago asked for), ie in effect buildingg a reinforced auxiliary spill-way, rather than the unreinforced one.)
The inadequacy here is not due to a planned failure at this point, but because they pretended that what they built would withstand anything that could be thrown at it in a worst-case scenario. The federal and state responses, brushing of the concerns of the petition claimed exactly that, that the e-spillway is sufficiently strong for a worst-case, and nott needing more.
Self-serving worst-cases of course, so as not to spend more money.
Engineers of a different mind-set, take the worst-case, and then do a 1.5-2x increase (see Roebling comment below).
The mentality is similar to the Tappan Zee Bridge (whose intended life-time was a reidiculously short period, and being of the same type of construction as the Minneapolis bridge, we see what that can mean).
I mention the TZB, because its from the same era of design as this dam.
Compare that to the Brooklyn Bridge.
Still standing after 133 years, because Roebling set no date for its demise, it was supposed to last indefinitely, and still going strong.
When they finally replaced the main suspension cables after a century, they were found to be in such good shape as to have not needed it.
And question again out of curiosity, how far below the 901 ft line does the main spillway drain?
If you cannot understand Trainer’s excellent video… I don’t know what else to say?!
https://dailytimewaster.blogspot.com.es/2017/02/breach-of-auburn-coffer-dam-in-1986.html
Thx to Trainer February 16, 2017 at 1:28 pm GK
They where small yes, but think when they are exaggerated by global warming or worse with climate change.
No one knows where it can lead, but for sure it might be much worse when all is concidered.
If the sky is not falling down, maybe the ground is.
G. Karst –
First off, I really enjoyed the video of controlled failure of an erosion plug at Auburn coffer dam. Every engineering geology and geotech engineer student needs to see it. However, I suggest that the Oroville scenario is somewhat different.
I have spent some time studying an aerial photo taken after the emergency spill. Whereas the Auburn coffer dam plug was clearly introduced fill, the Oroville emergency spillway appears to be built on insitu rock. This suggests that the design was based around a scenario where a sheet of water would spill down slope as though the surface was similar in nature to concrete.
The structure of the rock surface and the embankments of the erosion channels are consistent with metamorphic rock. There appears to be an upper bed (layer) through which the water cut channels rapidly. The floor of the channels appear to be a harder material. I say this because the channel walls are of a rather regular depth. This is consistent with metamorphosed lava flows, or subsurface sills – or even sedimentary sequences i.e. different layers with different properties. There is also the possibility that there is no layering and that the water cut though the weathered (rotten) ārindā. But, usually weathering is very inconsistent in depth.
Therefore, I speculate using this limited evidence that Oroville was not designed with an erosion plug. It was designed with a natural spillway surface that proved to be too weak. The danger could be that once the concrete structure was undercut there would be a rapid catastrophic failure resulting in a wall of water rushing downstream, rather than a progressive discharge as seen at the Auburn coffer dam.
Just one manās (geologist) analysis š
Do not get hung up on the word “plug”. The plug can either be natural or man made. It varies. in this case the majority of the plug is the emergency spillway itself. ALL dams are big plugs. in an extreme emergency Do you want to pull the big plug or the small self sizing plug
It took civilization centuries to learn a important reality:
ALL DAMS WILL EVENTUALLY FAIL
So we put out tenders for a new dam and powerhouse and we get two applicants:
– a geologist and an engineer. The geologist says he is building the dam on billion year old bedrock’s and he will build a structure which CANNOT fail, even when and with overtopping. I cannot tell you how it will fail because… IT WILL NOT FAIL
– an engineer says ALL DAMS CAN FAIL, if the unforeseen happens, and it will fail quickly if overtopped. Mine will fail like this and you will be back in business shortly after.
Who are you going to hire?
Well… for centuries we went with the geologists. Google famous historical dam failures to find out how that worked out.
Modern earthen dams have gone with the engineer. Just one man’s observation. GK
GK
Who would I employ? Well, find me a dam construction team that does not include:
Engineers (electrical, fluid dynamics, mechanical, structural, geotechnical)
Geologists: Engineering, structural, seismologists, geophysical
Others: Hydrology e.t.c.
The profession of engineering geology was first acknowledged in the US. It is an essential part of any team to analyse and predict the behavior of sub-surface materials
Remember that a dam has to be linked to natural materials. Below is an example of what happens when the geological studies get it wrong. In this case a slope toe was weakened by saturation. As I recall there was some seismic activity involved too