Oroville Flood

Very latest! Emergency spillway now being used....

http://www.sacbee.com/news/local/article132154774.html

on 42 I posted video of this 8 hours ago

No, you posted a link 6.5 hrs ago, and mine is clearly better....

ok it just seems that long

I agree too, except that he only mentioned the city of Oroville. If that dam were to catastrophically fail, Oroville would hardly be the only city affected. Gridley is only about 12 miles downstream, and is about 100 feet lower; Yuba City and Marysville are another 12 miles downstream, and another 40 feet lower. I've already mentioned the 1955 Yuba City flood. There are several other smaller communities along the way.

Then it's only another 40 miles to Sacramento. Most of downtown Sacramento has an altitude between 15 and 25 feet above sea level, while the altitude of the surface of the river is currently just under 30 feet ASL (http://www.water.weather.gov/ahps2/hydrograph.php?wfo=sto&gage=sacc1), before any dam break. There are levees to channel the river and "protect" low areas, but there is no way those levees would contain the flow from a broken Oroville dam, and it is inevitable that if the water rises to flow over the tops of the levees, then shortly thereafter, the levees will start failing entirely, and then...

The Yolo bypass around Sacramento is already flooded, so it would probably not help much...

This all sounds like the aforementioned ''serial disaster'' to me, from now, through the effects of the snow-melt, in July, 2017...

With which part?

I would have to say Scott Cahill makes a dam good answer there, and is making dam good sense. This is no laughing matter. If my family lived there, it would be time for a vacation somewhere far uphill of that mass of water.

Erosion

http://wwlp.com/2017/02/11/oroville-dam-rushing-water-takes-out-land/?anvt=83

That's a strange source for information on the event! ...but I have found an incredible dearth of local sources that are current, so that's understandable.

The few local sources are so plagued with advertisements, that it is extremely difficult to follow a story, or even find it. I briefly saw a headline about DWR Drone footage of the flow in the emergency overflow, but lost it before I could click on the headline.

There is also a LOT of misinformation. I've seen a number of articles talking about "allowing" or "opening" flow into the emergency overflow. There is no control whatsoever of that flow, other than controlling flows through the normal gates and the power station to lower the lake level. If the lake fills to the 901 foot level or higher, as it has now done, there is nothing they can do to limit the flow over the emergency spillway.

One somewhat comforting observation: the flow over the berm of that emergency spillway appears very uniform. This means that after sitting there unused for nearly 50 years, it is still quite level; no significant settling has occurred.

I've seen plenty of video of the emergency spillway flow into The Feather, looks very reddish like clay. It's been reported they're releasing full tilt for 40-50 hours to lower the pressure before the next storm is due on thurs. I think the chute is a total loss, I'll be rather curious to see the ruts.channels carved due to the emergency flow paths.

and yes I know the 2nd flow is 100% unregulated....if high enough it just goes over.

https://www.youtube.com/watch?v=OD3JEoQwD1U

The good news is that the side channel that undercut the normal spillway has washed everything down to bedrock, so it should be straightforward to add to the spillway based on that?

Seriously, it reveals something the original engineers did not take in account, and also provides a good solution to the issue at the same time.

I'm usually quite an optimist but that's getting challenged today. if this dam blows I would expect the base of the emergency spillway to be the lynchpin.

https://youtu.be/oQxVmKnBgvc

WOW! That video is indeed scary! That the parking lot appears to have become part of the emergency spillway is extremely troubling.

HOWEVER, I take some degree of comfort observing that there is a large block of rock separating the flow from the damaged spillway into two streams. This means that there is indeed bedrock there, so presumably the majority of erosion has already occurred, and the flow can be continued through that spillway and get the lake level down before the next series of storms arrives.

Fortunately, current forecasts indicate considerably smaller rainfalls in this next series than occurred in the previous series.

I don't think the main spill will be in play if we see a failure. they just never expected to even use the emergency so the slope is giving up up it's soil fast.

don't forget we still have Spring runoff coming

I don't think they have any choice! I suspect the erosion from water flowing over the emergency spillway will be vastly worse than that from the damaged main spillway. Fortunately, the upper half of the main spillway, including the gates, appear to be holding, so as soon at the soil is washed down to bedrock below the break, further erosion should be minimal.

They urgently need to clear the river at the base of the dam, so they can restart flow through the hydroelectric facility, even if they don't generate any power. That's the ONLY thing they can do to reduce the flow through the main spillway and/or prevent continued overflow through the emergency spillway. I know very little about what might happen to the turbines and generators spinning with no load, but if they must be sacrificed to save the Sacramento Valley and Delta, so be it!

Also fortunately, the forecasts currently show the next storm series to be colder than the previous series, so it won't be melting snow like the previous storms did.

I still say it was a wise choice to choose to live where I do!

I think they're gonna lose it

They honestly didn't think floodwaters would ever breach that car park? What is the difference in height between that and the emergency spillway? A couple of feet?

Looking at the construction of that chute, the terracing below the E.S. - and we know damn well any water spilling over it is going to chew that soil up like it wasn't there - and this whole dam is beginning to look like a bad joke. Let's hope there's some bedrock down below the E.S. and that car park or that water is going cut its own gorge.

That dude is really laying it out there as to what might be about to happen. Just another fine example of amateur hour government (demothugs) in power, and what they produce every time they are in place - pure chaos, ineptitude, and totally ignoring their job while they politik.

Video footage of the E.S. yesterday afternoon:

they say the emerg spill should stop flowing in a day or two, will any soil be left?

https://youtu.be/fA52L0eabNo

http://www.kcra.com/article/water-flows-out-of-emergency-spillway-at-lake-oroville-drop/8734513

massive soil erosion posted today

https://youtu.be/HLmkLhiPN1A

Time to bail out!

http://www.krcrtv.com/news/local/butte/evacuation-orders-for-low-levels-of-oroville/330519833

A hazardous situation has developed with the Oroville Dam emergency spillway. Officials say that operation of the auxiliary spillway has lead to severe erosion that could lead to a failure of the structure.

Failure of the emergency spillway structure will result in an uncontrolled release of flood waters from Lake Oroville.

.................OROVILLE, Calif. (KCRA) —

An evacuation has been ordered for low-lying levels of Oroville and several areas downstream from Lake Oroville, the Butte County Sheriff's Office said.

"Officials are anticipating a failure of the Auxiliary Spillway at Oroville Dam within the next 60 minutes (5:45 p.m.

Live coverage

https://www.youtube.com/watch?v=vwIst1YiMdo

That road is gone!

That little road is inconsequential. The impending failure of the emergency spillway is NOT!

It is really fortunate that we still have a few days of dry weather before the next storm series. Supposedly, the water coming over the emergency spillway is currently down to about 2 inches deep, and they just said (KCRA TV) that the level of the lake is dropping at about 4 inches per hour, so the flow should stop within the hour. At this point, whatever erosion occurs at the bottom of the main spillway must be accepted as inevitable, hopefully to avoid losing the emergency spillway.

On the other hand, if an edge of that parking lot has eroded below the top of the emergency spillway, we could still have major problems. Hopefully, the current evacuations will turn out to have been only precautionary. If not, I still fear for downtown Sacramento.

Officials say erosion not as bad as they thought

apologies for the lousy drawing. when the base of a hill erodes too much the weight of the top of the hill pushes in a downward force ( green arrow), this causes the base to blow out( purple arrow) and you have a big slide. this has been my fear since the water went over the top this morning

Is this cross-section in way of the emergency spillway, the controlled spillway, or somewhere else? Have any cores been been taken to assess soil saturation?

Your drawing is a good drawing for any hillside slope, whether it has a spillway, or not...

Amen...

Straight outta Bureaucracy 101 training ?...

Three days later from the original posting, there has yet been no flood. Of course, day 4 may be different, but this headline is still premature. (And any sensible person hopes that it remains so.)

there are about 200,00 people stuck in traffic jams right now that wish they had been following my thread

one doesn't know the damage you can't see. when it fails, you'll know it.

That's why the evacuation precautions are taking precautions.

FEB 13 2017.

Base if emg spillway once the flow stopped.

http://www.kcra.com/article/water-stops-spilling-over-oroville-auxiliary-spillway/8736758

better shot of same taken morning feb 13th 2017

That is better, but the links are better still.

You still haven't told us what your landslide/slumping drawing represented. Please do.

For the record: I think the plan that's currently unfolding to make helo drops of bags of rocks is completely hare-brained. It's nice to see effort but its a complete waste of time, it's all for show

Can't they construct a (very large) siphon tube or several smaller tubes that would not only bypass the hillside, but continuously lower the level of the lake until all repairs are made?

Of course doing that might be against california's strict water usage laws.

Ordinarily, powerhouse discharge would do this, but apparently that is now restricted by debris.

..and that's why they need to implement a siphon sooner rather than later. It would be time and money better spent than bags of rocks.

I don't think the water cares about those measly bags of rocks. It will sneeze those little boogers out faster than you can say ah-choo.

Sorry, but a siphon can only lift water over a barrier whose height is less that the height to which a vacuum can lift water at the local atmospheric pressure and temperature. At sea level and ordinary temperatures that height is just under 34 feet. At the 900 feet altitude of the dam, the distance will be a bit less.

To do any significant good, for this task, the pipe would have to be large in diameter, and we'd need many of them, because the flow rates would be small. The practical lift distance will be reduced by the diameter of the pipe, so if you choose a 4 foot pipe, the lift distance is reduced to something under 30 feet.

By the time you could get these siphons constructed and installed, they will presumably have the level of the lake well below the 870 foot level (the lowest the siphons can operate) simply by letting water out through the normal gates, as they are now doing.

You got me there.. I've done some math and upgraded to 16" impellers and 24" diameter flexible discharge tubes @~ 175 hp / 900 rpm / 25' head. and the number of pumps/tube required exceeds the available supply to overcome the 30/40,000 cubic feet per second flowing into the lake. GA from me

the power of water

this is what they want to fill in with rocks in bags via helo drops

What is that structure? It looks way narrower and less tall than the spillway chute. Neither of the "play" triangles activates anything, so no information is conveyed.

That's a concrete road that used to go across below the emergency spillway. They were using it today to dump rocks and to pump concrete...

I thought that might be it, but I didn't yet find the matching curve in the road. It looked pretty new, too.

it's the curve just above center , to the left of the gates and main spillway in this image:

Image from Apple Maps.

Most of the straight section north and west of the curve got washed away.

Thanks. I see it now. The tongue(s) of erosion inching upward toward the concrete part of the emergency spillway seem now to be of highest concern, especially if coming rains raise the lake level again.

I suspect the controllable spillway should be considered as expendable toast, under the circumstances. There will have to be expensive repairs later, but letting it go could minimize the immediate threats.

How close the erosion came to the weir.

update footage: mostly drone with a pretty detailed explanation. its shown on a small laptop but is informative.........Includes good shots of the helo bags being placed in the large holes at the base of the emerg spill.

Note: the blackhawks have a 9,000 lbs. lift capacity.

https://www.youtube.com/watch?v=XKW_YG1jq8A

Best drone view of emerg spill as it was eroding.

https://youtu.be/VBP-4ah3U6s?list=PLeod6x87Tu6eVFnSyEtQeOVbxvSWywPlx

I hope that all are well and also safe in this time.

I have two thoughts to share.

On the controlled spillway, I wonder if there has been water coming through fissures in the bedrock of the mountain, creating hydraulic pressure underneath the concrete and allowing it to then be compromised. We'll probably kow the outcome in a few years.

On the emergency spillway and the creeping of that undercut, does anyone know whether the authorities are taking the opportunity to raise the overflow surface locally at that point (even by just a foot or so) to reduce the concentration and duration of flow at that (now nearly compromised) point. That would require much less material and be more effective than filling the void in the hillside. (Just my modest opinion from my farming background.)

Casting a 1 foot high, 1 yard wide "pimple" across 60 yards would only need 20 cubic yards of concrete. Even with rough formwork would take less than 24 hours and is an engineering solution to the hazard.

Your first thought is indeed conceivable, and that water could either come from the water detained by the dam or simply from rainwater. Any such water may have been slowly washing away soil from under the spillway over a period of nearly 50 years, removing support for the concrete.

Unfortunately, most evidence of such erosion has now been carried far downstream. Perhaps they will be able to find evidence of it under the still intact portion of the main spillway. They need to use something like sonic testing or ground-penetrating radar to find out.

I disagree with your second idea. First, such an increased height would increase the level over the original design parameters, increase the pressure on the main dam, and increase the probability of collapse of the dam proper.

Second, that added berm would not only have to extend the length of the emergency spillway, but also across all of the parking area and its entrance to the hillside beyond. Of course it would have to be higher where it crosses the parking lot, to ensure that water only flows across the spillway.

Third, in a major storm event with the main spillway shut down or at reduced flow (as occurred to cause the recent disaster), all your "pimple" would do would be to delay overflow for a few hours, and make the results of a collapse even more disastrous.

I like to know what the details of the reports 10-12 years back, when it was reported there will be problems.

I had meant the "pimple" to be local to the area of the emergency spillway related to the scouring erosion and not the total length, so the effective TWL would be unchanged as water could still overflow along the rest of the spillway and only flow in that area if the level became 1' above the current level. Local reduction in scouring of that particular area.

I did not understand the limited length concept from your previous post.

Since the entire hillside was just soil over bedrock (with a considerable amount of the soil now gone), and was never shaped to direct the flow in any particular channel, raising any part of the emergency spillway would just concentrate the flow in some other narrower area and reduce the total flow for a given lake level. Thus the lake level would go higher for a while, take longer to come back down, and the now concentrated flow would scour a different part of the hillside with greater local flow.

As I see it, there are only a few choices: 1. Armor the natural channel(s) recently gouged out by the water and raise the sides of those channels to restrict the water to that/those channel(s). 2. Shape the hillside to guide the water into a chosen channel(s) and armor or pave that/those channel(s), 3. Armor the entire hillside.

I believe the wisest path would be a combination of #1 and #2, but that would probably take longer than #1.

Together with any of the above, they need to raise and reinforce the wall along the parking lot so water only flows over the spillway. This would require either a water-tight gate at the entrance to the parking lot, or raising the road at the parking lot entrance.

Good article on Engineering360 about the dam:

http://insights.globalspec.com/article/4201/highest-dam-in-the-u-s-faces-threat

That article does include some views I hadn't seen before. In the last image:

You can pretty clearly see the advancing edge of the erosion. It is clear that if that erosion (they called it a hole) had been allowed to advance further so it undercut the spillway, then water would have started going underneath the spillway, possibly causing collapse of the spillway, and definitely causing an uncontrolled surge of water.

I haven't seen any comment yet on whether the concrete weir of the emergency spillway extends down to bedrock all the way across. If it does, what looks like alarming erosion might be stopped.

(A sideline personal curiosity I have about all this is that a geology professor I once had, Howard A. Coombs, was a prime geological consultant on many Washington dams and nuclear facilities. I do not know if he had any input into the Oroville project.)

True! It certainly should be connected directly to bedrock, but I get the impression, since they never armored the hillside, that the original designers never expected the emergency spillway to actually be used. Of course it would still not have been used if the normal spillway had not failed.

I have a copy of an original feasibility study for the dam. When I have time, I'll see if I can find out who the geologists were (I presume there was more than one).

In plan view, the dam is arched a bit. That is a common feature in tall and/or thin-shelled concrete dams with geologically strong abutments, but not so common in earthen or other dams relying principally on their own weight to resist upstream pressure.

Correct, which is why I have suspected that the designers were depending on that (hopefully) geologically stable bedrock to maintain the position and integrity of the dam.

I have just noted in another thread (started today) that there is was a third line of defence (bypass valves for the dam) that aparently were confirmed as "failed" in 2009.

Maybe there is some investigation of how they might be restored at this time.

Thanks! WOW! I hadn't heard about that/those! If true, it's another case of terrible judgement and shortsightedness. Eight years without repair is totally inexcusable and unacceptable. This is especially true considering that the drought had the lake at extremely low levels, so the pressures in the areas of concern were at their lowest.

Perhaps these bypass valves are/were intended to bypass the turbines of the electric power plant. If so, they would presumably use the same exit channels used by the water from the turbines. Those exits appear to be in usable condition, although I understand that the concrete and other rubble washed down from the main spillway has blocked that channel, such that the turbines can't be used.

I think the turbines are still in service, but cut back severely due to the issue with partial blockage of the turbine exhaust channels downstream of the plant.

What is the thread's title? In a quick look, I didn't find anything that fit.

"Will It or Won't It? The Oroville Dam's Potential Collapse", the featured post on today's Daily Digest.

I looked only on the All Threads list.

You had me at "C4"..

Your "solution" (probably) creates additional challenges that the whole state would need to understand.

Most such valves are at "Scour" level within the dam. The outlet point would probably be at the same level as the power station outlets and the flow rate (with the nominated blaockage from downstream debris) would probably flood the hydro plant. If the vale and control mechanism are damaged beyond use, then you are talking about total draining of the dam. Then, all river flow would continue through that orrifice until an alternate outlet was commissioned, coffer dam or similar built to isolate this outlet for repair and so on.

In the meantime (years) the services provided by this dam would be reduced to merely a flow control device,no storage, no power generation etc. The country would lose the economic benefit the damprovides.

People closer to the total situation would be weighing the risk benefit and might even decide to breach that valve but probably not in the way that you described. In an clay/earth core dam such actions could enable coring along the pipe with catastrophic effect.

Does anyone here know the style of valve that was installed and the configuration. There should be a secondary upstream (Normally open) valve to enable service on this valve that is normally closed. The upstream valve would not be suitable to control flow (meant to be operated only in no-flow condition) But might enable access for less drastic modifications such as install a smaller diameter valve that can be controlled.

If valve move just enough to restart the previous seep, then that's good. We have "frozen" valves that need to be "exercised" up to 30 times before movement happens. If there is some movement, then each cycle allows the hardware to work through. Of course, my 1500mm valves are of significant scale different that Oroville.