Oroville Dam Spillway Failure

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There's something I don't really understand. At first, when the emergency spillway was used, we saw large amounts of erosion. The damaged main spillway was then used again to relieve the emergency spillway. The managers did so, knowing they would destroy their damaged spillway under that force of water.

It took this community a couple of days to find enough old drawings and documentation to show that the weir is solidly anchored to bedrock, and is so heavy that the water won't force it from its place. Assuming a well functioning archive, you'd expect the managers of the dam to have had that info within minutes to a couple of hours. What then did make them fear for a failure of the top of the emergency spillway, if the erosion couldn't have undercut the weir?

I think its pretty simple. Everything was going ok with the release over the emergency weir. Then all of a sudden they noticed erosion begin as the flow increased. That erosion was back cutting pretty quickly toward the weir.

They had an emergency they felt had to be addressed immediately, regardless of what they might know about the data. They felt they could not take a chance. It was actually the Sheriff I believe who made the call.

It quickly became apparent the erosion was likely just weathered surface material, as officials noted the erosion all but stopped after the initial burst.

In a perceived potentially large scale emergency you must act quickly - you have no time to dig thru documents and plans, or spend time discussion ... and you cannot trust anything anyway.

I'm pretty certain they threw every resource they have - including an army of engineers, both inside and out - at it as soon as it was stable ... and they reviewed every shred of data and information they had.

It seems telling they were not more aggressive at the work, and extent if the work, they completed on the bench below the weir ... if they had any doubts they would have spent far more time hardening from the base of the weir out along its entire length ...
 
BUCKS LAKE SWE 17-02-2017 12-32-47 AM.jpg

Is that 800,000 ac-ft range estimate for quantity of rainfall only or does the model include accelerated snowmelt?
A great many of the stations within the watershed show significant significant amounts of Snow Water Equivalent (SWE). Fresh snow may be up to 90% entrained air. This late in the season, after a number of melt/freeze cycles, and the effects of the January storm, there is much as 36" of SWE.

I might have a ballpark model done tomorrow. I'll post it in the other thread. Regarding snowmelt, see my recent post in the other thread - it doesn't seem to make a whole lot of difference, maybe a little. My very rough model will cover snowmelt, very roughly ;)
 
What falls at any single station, including the reservoir isn't a good gauge of what flows into the reservoir, since the drainage basin is a whopping 3600 square miles. But I am finding the basin-wide data I need.

I'm confused. I was not reporting what fell at any one station ... I showed the effect on the inflows and increase in water in the reservoir as a result of that January storm - which all seems to agree was a big one ;-)

How is looking at the ORO data - not an accurate representation of what flows into the reservoir?
 
Its more interesting to look back to 1995 ... appears the reservoir has been to 900' many times ... the number and share of time above 850' is small, but these levels aren't seemingly unprecedented ...

OrovilleDamLevels1995-2017.jpg

Yes, but what's different about this year is it has reached 900 early. Normally, it doesn't reach that level until June or so with the snowmelt.



There's about 3 million ac-ft of water sitting in snowpack, so they are going to have to run the spillway quite a bit.
 
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The spillway headworks has 8 gates.
Then why do we see only 7 plumes in all the photos of the spillway in use? For instance

The turbulence is a result of the piers between the gates, so 8 gates and 7 piers. The water passing through the throat of the gate is essentially laminar when the gate has head pressure.
 
SpillwayBedrock_emergencyWeirSide.jpg
The spillway headworks has 8 gates.
Then why do we see only 7 plumes in all the photos of the spillway in use? For instance...
Looks like the turbulence and "plumes" are caused by the (seven) walls between the gates, not the gates themselves.



I'd guess the force of the flows coming back together forces some of the water upward.
 
Obviously it wasn't planned as good if they rated it for 250k CFS and it failed under 12k CFS in under 2 days. This makes me question if they spent the time to do it right. Or do you think they spent all of the time and were wrong about the hillside?

It didn't fail. Someone thought it might fail.

And the hillside, other than the bench at the base of the weir, performed admirably. Despite the 12,000 cfs flow from the entire 900' weir consolidating on mostly one channel, there was minimal erosion if any once it reached the strong bedrock.
 
Yes, but what's different about this year is it has reached 900 early. Normally, it doesn't reach that level until June or so with the snowmelt.



There's about 3 million ac-ft of water sitting in snowpack, so they are going to have to run the spillway quite a bit.

Agreed ... I was more referring to the operation - that levels had reached similar levels in the past ... not necessarily the timing ...and yes - they must carefully and actively manage the levels and storage capacity to accommodate that melt. Add that a lot of it is old snow - with lots of water content.
 
Can anyone answer: Why are they continuing to attack the erosion below the parking lot with the extremely tedious, slow and (dare I say) expensive method of dropping bags of rocks by helicopter? Why haven't they pushed that road further so that they could simply fill those area with rocks delivered by truck?
 
I might have a ballpark model done tomorrow. I'll post it in the other thread. Regarding snowmelt, see my recent post in the other thread - it doesn't seem to make a whole lot of difference, maybe a little. My very rough model will cover snowmelt, very roughly ;)

I posted an overview of Northern CA reservoir storage in the other thread. Many locations close to 100% of capacity. I'm not in the neighborhood at the moment, but if I was I think I would be looking for my 10 gallon boots. Roughly.
Cheers!

The forecast thread is here:
https://www.metabunk.org/oroville-w...-inflow-calculations.t8406/page-3#post-201468
 
What falls at any single station, including the reservoir isn't a good gauge of what flows into the reservoir, since the drainage basin is a whopping 3600 square miles. But I am finding the basin-wide data I need.

But I wasn't using inflows ... I was using actual reservoir levels - the change, the increase, in how much water was actually IN the reservoir.

In this measurement it doesn't matter how much rain actually fell (other than generally as a reference - big, small, huge etc) it matter how much the water in the reservoir increased ...

IE: 'there was a big ol storm that dumped a lotta rain in the area ... and (as can be tracked by inflow level changes) this much water ended up in the reservoir during that period.'

For this purpose I'm only looking at the effect the storm at that time had on increasing water level in the reservoir ...

Still not sure why using the change in reservoir capacity isn't a proper measure of that?
 
Can anyone answer: Why are they continuing to attack the erosion below the parking lot with the extremely tedious, slow and (dare I say) expensive method of dropping bags of rocks by helicopter? Why haven't they pushed that road further so that they could simply fill those area with rocks delivered by truck?

There is a finite capacity to get materials to the work area - its a single lane across the main spillway and across the new haul road. The helo's offer additional capacity. I suspect its also because using the bagged rocks has its own value ... they are like a 2500lb boulder - in weight and size - but when placed - their 'elasticity' (smaller rocks in a bag) allows tighter fits than large boulders. A bit of the best of both worlds ...
 
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I have wondered such things but in reality it could equally have been the job of an up and coming young engineer with a lot of talent that did not get as much input as would have liked on the main dam, and did the job on the emergency spillway far better than average. There is just no way to know about things like that and while I wholeheartedly agree that government is sort of incompetent in a general sense, engineers do it because they are into it and think it's cool mostly, and most care about their engineering.

I just want to point out Ken was actually disagreeing with the comment about engineers treating the emergency spillway as an afterthought ... pointing out it could also have been a young engineer who may well have paid more attention and done the work better than average ... its an important distinction that should be noted
 
Have they said how far they plan to drop the water level? What would be the reason to stop at 850' instead of continuing to draw it down to 813.6', weather permitting?
 
Have they said how far they plan to drop the water level? What would be the reason to stop at 850' instead of continuing to draw it down to 813.6', weather permitting?

850 is the design "flood control" operating level for the dam. Reducing much further below 850 requires lower flows due to the intake channel and other considerations. I suspect they will overshoot by a little but then manage outflow to maintain around that level.

The last briefing I saw Fri I believe they noted they expected the storm total inflow to increase level to about 861 ...

Inflows have increased in last 8 hours or so to be consistently around 40,000 cfs ... outflows holding steady at appx 55,000 cfs .... levels still dropping - but only appx 1 inch per hour instead of 4 or more ...
 
Its more interesting to look back to 1995 ... appears the reservoir has been to 900' many times ... the number and share of time above 850' is small, but these levels aren't seemingly unprecedented ...

OrovilleDamLevels1995-2017.jpg

I suppose it's sort of "neat" in a way, that the time I went there in late 2014 it was only about 10 feet above its lowest stage during the timespan of this graph. For me at that time, the lake's level was about 242 feet below capacity.
 
There is a finite capacity to get materials to the work area - its a single lane across the main spillway and across the new haul road. The helo's offer additional capacity. I suspect its also becasue using the bagged rocks also has a value ... they are like a 2500lb boulder - in weight and size - but when placed their 'elasticity' (smaller rocks in a bag) allows tighter fits than large boulders. A bit of the best of both worlds ...

And not only that, but when you pump fast drying grout / concrete on top of those very heavy Hershey Kisses they make very excellent water immovable plugs.
 
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850 is the design "flood control" operating level for the dam. Reducing much further below 850 requires lower flows due to the intake channel and other considerations. I suspect they will overshoot by a little but then manage outflow to maintain around that level.

Can you explain what "flood control operating level" implies? I've seen and understood the graph showing that the output goes down rapidly as the level falls and approaches the 813.6' limit.
 
And not only that, but when you pump fast drying grout / concrete on top of those very heavy Hershey Kisses they make very excellent water immovable plugs.

Which they'll be unable to do until they push the road over there to get cement trucks and pumpers to the site. And if those bags are so much more valuable than just loose rocks, wouldn't they also be loading them onto the trucks for the repairs they're currently doing?
 
Someone else can probably describe it far better - from the CA AWR:


For federal projects, or as a condition of federal cost sharing on other projects, USACE (U.S. Army Corps of Engineers) prescribes rules for operating reservoir space dedicated to flood control.

By mid-October each year, Lake Oroville storage must be reduced to a specified level within the range of a maximum flood control pool of 750,000 acre-feet and a minimum flood control pool of 375,000 acre-feet. The allowable level within the range is recalculated each day, using an index that reflects the wetness of the watershed and the likelihood of heavy runoff from any incoming storms. As a wet season, such as in 1997-98, progresses the allowable storage tends to coincide with the maximum flood control pool.

When high inflows occur, water is temporarily held in the flood reservation as necessary to maintain reservoir releases within prescribed limits that are designed to prevent downstream damage. The downstream flow limits set by the USACE for Lake Oroville are 150,000 cfs north of Honcut Creek, 180,000 cfs above the mouth of the Yuba River, and 320,000 cfs south of the Bear River.

While water is being stored to maintain releases within target levels, reservoir storage may exceed the level allowable under the flood operating criteria, a condition known as "encroachment" into the required flood reservation. The USACE criteria recognize that such encroachment will occur and establish release criteria for such conditions.

Reservoir operators must balance the conflicting objectives of controlling the current flood event and preparing for a possible future one: the encroachment is eliminated when downstream conditions permit.
Content from External Source
 
A deep erosion channel cut by 15k cfs, that headcut its way toward the emergency spillway, is circled in red.
erosion of e smillway overview.jpg
A photo taken from within this hole shows the rock.
brecciated bedrock.jpg
As opposed to the competent gray sheeted dikes composed of diabase, this rock appears to show breccia, which can be formed in a fault. However, in this setting situated at a mid-oceanic ridge, there is another process that forms breccia. Mid oceanic volcanoes at spreading centers erupt magma, whose flows can form rocks known as pillow lavas. The rapid cooling by seawater causes rapid cooling on the exterior surface, called chill margins, can produce glass, with chunks often breaking off that tumble down and form piles. Here is a video of this process, note the chunks falling off.
Source: https://www.youtube.com/watch?v=hmMlspNoZMs



At some point later, as the plates continue to pull apart, magma forces its way up and through the accumulation of overlying basalt, forming the sheeted dikes. This results in the juxtaposition of compositionaly similar, yet characteristically different material very near each other. More reading on ophiolite basalts and sheeted dikes here http://jersey.uoregon.edu/~mstrick/GeoTours/Josephine Ophiolite/JoOphiolite.html#Basalt
smartville ophiolite strat column anotated.jpg
Stratigraphic column from Menzies http://earth.geology.yale.edu/~ajs/1980/ajs_280A_1.pdf/329.pdf

Water circulates through the oceanic crust near the spreading center, being drawn down close to the hot magma where it is super heated and gains many minerals. This hydrothermal fluid follows paths of least resistance, such as a pile of brecciated rock, where it interacts with that rock causing alteration. Here is a diagram:
vents2.gif
http://oceanexplorer.noaa.gov/explorations/02fire/background/vent_chem/ventchem.html
This hydrothermally altered basalt can be very weak, as the modest flows that carved this channel have shown.

Possible hydrothermal alteration.
yellow hues.jpg

Further troubling the situation is the dip of the layers is towards the emergency spillway and main spillway gates. So even if the spillways are on competent bedrock, there are possibly incompetent layers extending under them.
big hole.jpg

Layers of altered material extend deep under ground (outside blue lines). This hillside is at the north end of the parking lot, 1968.
back parkinglot 1968 anotated.jpg

In regards to Steven Ward's simulation, with the parameters of his fail being 600m x 25m, I see it as a possibility, however slim. Imagine the main spillway fails to the extent that it is shut off, and a train of AR's arrive after the one currently over the horizon. Without steel reinforcement, bolted to the bedrock, and under slab drains, the current concreting, under sustained flows over a 100k cfs for extended periods, will be like putting a band-aid on a gangrene leg. Imagine the average flow of Niagara falls at 85k cfs going over, things would deteriorate rapidly.

Headward erosion could migrate from the yellow zone, into the green zone, unleashing the blue arrow. As flows continue, the ogee weir gets undermined, goes over the falls, taking the main spillway gates with it. Unlikely, but possible.
possible progressive failure.jpg

Considering the incompetence of the bedrock below the emergency spillway, both spillways should be sunk much deeper into the ridge.

The theory of sea floor spreading at mid oceanic ridges was first proposed by Harry Hess in the 1960's (http://www.mantleplumes.org/WebDocuments/Hess1962.pdf). I doubt whether any geologist working in the late sixties would have been able to fully understand the geology at Oroville dam in those terms. However, how they didn't foresee the weakness of rock below the e spillway is strange.

All photos images not cited are from http://pixel-ca-dwr.photoshelter.co...yfg/G00003YCcmDTx48Y/Oroville-Spillway-Damage
 
Which they'll be unable to do until they push the road over there to get cement trucks and pumpers to the site. And if those bags are so much more valuable than just loose rocks, wouldn't they also be loading them onto the trucks for the repairs they're currently doing?

Trucks are more valuable to move rock. And, how do you get them outta the truck? Just dumping them defeats the purpose - the helos are pretty good at precisely placing them to minimize voids.

As to the cement trucks they don't need much of a road ... and the pumpers are typically offroad capable and have long reaches. I bet they could also use fire type water drop bags to deliver grout by helo as well if they put their mind to it ...
 
The use of helicopters to me indicates they are in full speed ahead every method possible frame of mind. It is risky to run helicopters over ground crews. It is very risky to fly helicopters below the altitude they can safely initiate an autorotation maneuver if they lose power (though the UH-60 is twin engine specifically for that military requirement).
UH60autorotationenv1.jpg

This shows that at the altitudes and speeds the helicopters are working they have little chance at choosing any landing area and very little ability to flatten then reverse the pitch on the blades, drop the suspended cargo if present, drop altitude and use that to accelerate the rotors then increase pitch on the blades and flare for a landing. Flying low and slow in a helicopter is its most vulnerable position.

The insurance for this, I am not sure how that works but helicopter and construction sounds incredibly expensive to me.

Can anyone confirm or deny these admittedly non expert opinions?
 
The use of helicopters to me indicates they are in full speed ahead every method possible frame of mind. It is risky to run helicopters over ground crews. ...
(snipped)
The insurance for this, I am not sure how that works but helicopter and construction sounds incredibly expensive to me.

Can anyone confirm or deny these admittedly non expert opinions?

They have the two helo's (when I was observing them on video), staggered, So one is over the lake, and one is over the Dam side, perfectly tag teaming. They are also staggered by height so not flying level. So 1/2 lap per minute or so. One rock every minute arriving.

The crew are flying in a designated formation approach, like clock work. They are offset in altitude. The bags are used specifically where they are needed most, now. The trucks will prob build a road over to there as we discuss this. Once they declared emergency, this has been handled professionally.

The helo's also are a sign to the public that everything is being done, who had been ordered to evacuate due a risk in the loss of control of the E structure. I expect they keep working on the E spillway LONG past the point it needed any more work done on it. This is now also a political event in front of America. Everyone is watching.

Disclosure: former wild land firefighter. hand crew. 4 seasons. 7 US States. Have been flown to remote fires by helos hired for the job. One of my fav pilots rolled at 103% of throttle and would throttle up to 108%. Everything, is a design spec.
 
They have the two helo's (when I was observing them on video), staggered, So one is over the lake, and one is over the Dam side, perfectly tag teaming. They are also staggered by height so not flying level. So 1/2 lap per minute or so. One rock every minute arriving.

The crew are flying in a designated formation approach, like clock work. They are offset in altitude. The bags are used specifically where they are needed most, now. The trucks will prob build a road over to there as we discuss this. Once they declared emergency, this has been handled professionally.

The helo's also are a sign to the public that everything is being done, who had been ordered to evacuate due a risk in the loss of control of the E structure. I expect they keep working on the E spillway LONG past the point it needed any more work done on it. This is now also a political event in front of America. Everyone is watching.

Disclosure: former wild land firefighter. hand crew. 4 seasons. 7 US States. Have been flown to remote fires by helos hired for the job. One of my fav pilots rolled at 103% of throttle and would throttle up to 108%. Everything, is a design spec.

As a Californian that has has seen a home leveled and felt the heat of an out of control fire, THANK YOU FOR YOUR SERVICE!!!

I agree with your assessment, just wondering what the actual administrative burden is of using aerial construction. How much risk assessment is changed, how much DWR operating insurance goes up from counting up minutes with a particular method of moving rocks.
 
A deep erosion channel cut by 15k cfs, that headcut its way toward the emergency spillway, is circled in red.
erosion of e smillway overview.jpg
A photo taken from within this hole shows the rock.
brecciated bedrock.jpg
As opposed to the competent gray sheeted dikes composed of diabase, this rock appears to show breccia, which can be formed in a fault. However, in this setting situated at a mid-oceanic ridge, there is another process that forms breccia. Mid oceanic volcanoes at spreading centers erupt magma, whose flows can form rocks known as pillow lavas. The rapid cooling by seawater causes rapid cooling on the exterior surface, called chill margins, can produce glass, with chunks often breaking off that tumble down and form piles. Here is a video of this process, note the chunks falling off.

Further troubling the situation is the dip of the layers is towards the emergency spillway and main spillway gates. So even if the spillways are on competent bedrock, there are possibly incompetent layers extending under them.
big hole.jpg

Layers of altered material extend deep under ground (outside blue lines). This hillside is at the north end of the parking lot, 1968.
back parkinglot 1968 anotated.jpg

In regards to Steven Ward's simulation, with the parameters of his fail being 600m x 25m, I see it as a possibility, however slim. Imagine the main spillway fails to the extent that it is shut off, and a train of AR's arrive after the one currently over the horizon. Without steel reinforcement, bolted to the bedrock, and under slab drains, the current concreting, under sustained flows over a 100k cfs for extended periods, will be like putting a band-aid on a gangrene leg. Imagine the average flow of Niagara falls at 85k cfs going over, things would deteriorate rapidly.

Headward erosion could migrate from the yellow zone, into the green zone, unleashing the blue arrow. As flows continue, the ogee weir gets undermined, goes over the falls, taking the main spillway gates with it. Unlikely, but possible.
possible progressive failure.jpg

Considering the incompetence of the bedrock below the emergency spillway, both spillways should be sunk much deeper into the ridge.

Your position however disregards the documentation that shows the builder went to extra effort and expense to identify competent bedrock below the spillway, and overcut and backfill with concrete any imperfect areas.

Your position also presumes that the engineers and builders at the time did not understand the composition of rock in the area, which I think is pretty preposterous. The properties you note are not new discoveries. More, or perhaps most, importantly these experts spent decades excavating and working int these areas.

You also discount that most, if not all, your yellow area, and indeed most of the bench, and slope to the access road, has been filled with competent rock and grouted - in some places as much as 25 or more feet deep. Also that a less robust version of this rock and grouting was done at the base of the weir at the main spillway end - where the weir is nearly 60 feet tall ... and performed without erosion.

At minimum this armoring has moved any erosion downslope to the access road and beyond.

You note, but don't acknowledge, that almost all the erosion is in the weathered surface area rock. In fact the erosion on the flat bench below the ogee weir at the parking lot end that authorities were so worried about ... that was rapidly backcutting toward the weir, was reported to have stopped its rapid advance and erosion shortly after the evac decision was made. Indicative that it was the weak weathered surface layer rock, and once it was eroded and more competent subgrade rock was encounter the back cut slowed and/or stopped. Keep in mind this rock has been exposed to the elements for 50 years

You also I believe fail to consider the base of the ogee weir is well below existing surface grade. There is at least a 12' wide apron or "toe" on the downslope side of the weir, that is shown as 6' thick. Then there is the bedrock foundation which is reported grouted and concreted as necessary. The backcut would have to be substantially deep to cut under the bedrock and weir itself.

I think you discount the clear presence of blue-green bedrock exposed during the event. The entire channel from the access road down to the river is shown to be blue green bedrock, and despite that nearly the entire flow from the emergency weir consolidated and flowed down this channel, there was minimal erosion and seemingly none in its base.

We also have photo evidence of exposed blue green bedrock at appx the 850 elevation to to the emergency weir side of the main spillway at the top - immediate adjacent to the emergency spillway.

We know the main spillway end of the emergency weir's base next to the main spillway (and the 850 elev exposed bedrock next to it) is at least 11' below existing grade there. This means the bedrock foundation begins at appx 836 elevation. We also know existing grade on the reservoir side is appx 875 - meaning the base is nearly 40' below grade on that side.

From my limited knowledge of the area and information in these threads, including from you, this is an upthrust area and these seams are vertical in nature. We can see this by numerous photo examples including from you. As such, as i understand it, it would be unlikely to find a seam below existing bedrock.

We know there were no seams like this in the bedrock foundation of the ogee weir - as the builders noted they removed any marginal rock and back filled with cement. Again - I fully trust these engineers and the like were fully competent having worked with and on this site from the 1950's and then thru the years of massive excavation and construction - including tunneling - throughout the area, and well understood exactly what they were working with.

Test borings were done, including in the spillway area down several hundred feet as well. Add that to the clearly identified areas where competent bedrock is exposed and I believe there is high confidence in the locations of bedrock in the area.

Again these were highly experienced and competent engineers and builders. To me - a suggestion they did not fully fully and completely understand the subsurface conditions - does not seem credible.

I DO have concerns with the parking lot extension of the emergency spillway. It is embedded just 4' in the ground. And absent the access road it is a shard drop from the bench below it - which was eroding as it sloped to the road.

That said your "green area" assertion fails I believe to consider that the grade on the reservoir side of that end of the ogee weir is within appx 6 feet of the top of the ogee weir - at 901 elevation. AND that it is appx 500 feet of flat ground at mostly that higher elevation, before reaching deeper water. The shallow depths over that 500+/- feet would see a moderate flow even in the chance a backcut migrated that 500 feet to deeper water ...

Your scenario that a backcut around the end of the ogee weir would topple it is simply not in my opinion credible.
Again - there is existing grade nearly to the top of the wall on the reservoir side there. And we know there is competent bedrock below it. Any backcut would migrate away from the end of the ogee weir due to all these "hardening" factors.

Last ... the same construction reports that informed us of the extent of extra effort and expense builder incurred in insuring competent bedrock below the ogee weir, also tells us a few more important relevant facts:

"Emergency Spillway. The grout curtain was continued under the left reach of the emergency weir near the upstream face, and formed drains are used under the downstream half. The crest of the emergency weir to the right, which is only 1 foot above the excavated channel, is keyed 2 feet into the foundation. Both weir sections were checked for overturning and shear friction safety factor and found to be satisfactory.

In part of the emergency spillway, an additional 10 feet of excavation was required to reach acceptable foundation rock, resulting in considerable additional time for excavation and placement of the backfill concrete to subgrade.

Approximately 90% of the chute foundation required blasting to reach grade
"

My opinion... YMMV

Areas we know good bedrock is identified:

Bedrock-EmergSpillway_1.jpg Bedrock-hillside.jpg
 
They have the two helo's (when I was observing them on video), staggered, So one is over the lake, and one is over the Dam side, perfectly tag teaming. They are also staggered by height so not flying level. So 1/2 lap per minute or so. One rock every minute arriving.

The crew are flying in a designated formation approach, like clock work. They are offset in altitude. The bags are used specifically where they are needed most, now. The trucks will prob build a road over to there as we discuss this. Once they declared emergency, this has been handled professionally.

The helo's also are a sign to the public that everything is being done, who had been ordered to evacuate due a risk in the loss of control of the E structure. I expect they keep working on the E spillway LONG past the point it needed any more work done on it. This is now also a political event in front of America. Everyone is watching.

Disclosure: former wild land firefighter. hand crew. 4 seasons. 7 US States. Have been flown to remote fires by helos hired for the job. One of my fav pilots rolled at 103% of throttle and would throttle up to 108%. Everything, is a design spec.

Yep ... pictures from Friday- still working - in the rain ... and they are not kidding around:

BB_Oro_Spillway_damage-0664_2_17_2017.JPG
 
That photo may offer a better reason for why they don't/can't push the road further. The erosion channel just above the one circled looks to be as deep or nearly so, and not something they're going to fill in a couple of days.

* Edit *

But it another photo just above, it looks like they have that channel taken care of. Can't quite say it's completely filled in, but it's been stabilized with rock and cement.

 
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Further troubling the situation is the dip of the layers is towards the emergency spillway and main spillway gates. So even if the spillways are on competent bedrock, there are possibly incompetent layers extending under them.
big hole.jpg

I'm not sure what is troubling about it ... that there's a hill son ... you can go up and down 'em ...
... and the emergency weir sits on the top of the hill ... and that would be the down direction ... ;-)

Oh, and as to the parking lot? most of it was originally 920 to 940 elevation - just under 900 now ...

20170215_50overlay.jpg

20170215_NewLabelsOldMap.jpg
 
I'm trying not to overthink the current situation.

The auxiliary spillway did not fail.

Did it perform as well as it was designed to do, no. I'd give it a fail, not an epic fail mind you.

It was it's 1st test after all.

The prudent thing to do was done.

Save lives because "we" don't know exactly what's going on or is about to happen.

If the powers that be are trying to fix the situation as best as they can in anticipation of Murphy's Law they should throw whatever tools are safely available to them in the present to fix the problem short term.

(A whole lot of water is yet to come through that choke point in the months that come).

Plenty of finger pointing will come soon enough.

You can fix and repair dams, human lives lost you can not undo.
 
That photo may offer a better reason for why they don't/can't push the road further. The erosion channel just above the one circled looks to be as deep or nearly so, and not something they're going to fill in a couple of days.


The erosion area above the red circle is fully filled and armored with concrete. It was filled over the course of a couple days last week.

Pretty much the entire area from the emergency weir to the access road is filled and hardened with concrete.

Plus what the accomplished yesterday and today ... judging by the cement trucks lined up the work they did was pretty major ...
 
I'm confused. I was not reporting what fell at any one station ... I showed the effect on the inflows and increase in water in the reservoir as a result of that January storm - which all seems to agree was a big one ;-)

How is looking at the ORO data - not an accurate representation of what flows into the reservoir?

Average rainfall over the entire 3600 sq mile basin correlates to what flows into the reservoir. To do any kind of rough comparison of this storm vs the last, you need that number.
 
850 is the "flood control" elevation ... their normal drawdown minimum.

And we should all remember that this reservoir is an integral part of a state water control project which provides both flood control, and water availability (and electricity). Flood control prevents taking the primary spillway out of commission for an extended period and letting the emergency spillway retard (incapable of "control") the flood. Water provisioning prevents draining the reservoir so that the primary spillway can be dry for several months.

Snowpack in the watershed is far above normal at this late stage of the season, so there's plenty of water available. But it's not easy to predict the demand for it over the next several months since so much of that demand is agricultural and seasonal precipitation forecasts have variable consistency and confidence.
 
That's the road over the dam, isn't it? It certainly looks like it's capable of two-way traffic.

That isn't the problem - it is the road across the main spillway to get to the emergency spillway side and the haul road onto the emergency spillway benchFL_Oroville-2490_02_14_2017.jpg KG_oro_spillway_damage-11907_02_13_2017.jpg ...
 
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