Home Forums Hunting & Shooting Hunter's Campfire Oroville aux spill to fail within the next 60 min!!

As of this morning, they've canceled the evac order for now.

Yep - it's definitely a fluid situation.

Good read (s),....and the BEST pics yet

Link: http://www.forbes.com/sites/davidbr...ations-on-the-oroville-dam/#6ea5a5c91925

Link: http://blogs.agu.org/landslideblog/2017/02/14/oroville-dam-site/

Some Geological Observations On The Oroville Dam


David Bressan , CONTRIBUTOR
I deal with the rocky road to our modern understanding of earth

Opinions expressed by Forbes Contributors are their own.
After copious amounts of rainfall in California in the last weeks, the artificial lake of the Oroville Dam is now filled far above its normal capacity. To hold the lake level at a maximum of 20 feet below the crest of the dam, the additional water can be discharged by a main spillway and an emergency spillway. Last week, cracks and a 300 feet wide hole suddentlyopened in the concrete of the main spillway. After a first inspection of the damage, a discharge test to lower the water level in the lake was undertaken, which caused more damage to the spillway. Reducing the discharge slowed down the damage done to the main spillway. However, Lake Oroville has been rising in response to the reduced outflow at the rate of about half a foot per hour in the last week.

Discharge test February 11, 2017 at the Oroville Dam. In the background the concrete weir and the emergency spillway are visible. The main spillway is already damaged and running water started to erode the left bank of the spillway. Image by William Croyle, California Department of Water Resource, work is in the public domain.
Discharge test February 11 at the Oroville Dam. In the background the concrete weir and the emergency spillway are visible. The main spillway is already damaged and running water started to erode the left bank of the spillway. Image by William Croyle, California Department of Water Resource, work is in the public domain.

As planned, as the lake level rises, the water pours over a concrete weir into the emergency spillway, which is parallel to the main spillway and has a capacity of 15,000 cubic feet per second. However, the actual inflow into the lake is still twice as much as the limited outflow. The unforeseen amount of water (the emergency spillway had never been used since the dam was completed in 1968) started to erode an area of earth downhill the weir.

Discharge test February 11, 2017 at the Oroville Dam. In the background the concrete weir and the emergency spillway are visible. The main spillway is already damaged and running water started to erode the left bank of the spillway. Image by William Croyle, California Department of Water Resource, work is in the public domain.
Discharge test February 11 at the Oroville Dam. In the background the damage done by erosion in the emergency spillway is visible. Image by William Croyle, California Department of Water Resource, work is in the public domain.

The actual danger here is that the headward erosion will erode the slope up to the base of the weir, causing the collapse of the concrete wall of the emergency spillway. (The Oroville Dam itself is at no risk of spillover or even collapse, however). This worst-case scenario would send a 30-foot-wall of water down the Feather River, a tributary to the Sacramento, flooding areas along the Feather and Sacramento River.

According to available geological maps, the Oroville Dam is build on the Smartville ophiolite, consisting of dark grey, steeply-dipping and strongly foliated metamorphic rocks. Once of volcanic origin, erupted in an ancient sea, the rocks were uplifted and metamorphosed during the formation of the Sierra Nevada.

Geological map of Lake Oroville with the Oroville Dam in the lower left corner and geologic legend. Rocks of the Smartville ophiolite in green, tectonic faults are depicted as black lines. California Department of Water Resource, work is in the public domain. Thanks to user @may_gun for the links.

This description seems to match the rocks visible in published photos of the main spillway damage. Some comments have also suggested that the first hole in the main spillway developed above an altered zone of rock, as its more brownish coloration would suggest. Altered rock is more permeable and prone to erosion than massive rock. It's possible that water infiltrated below the concrete of the spillway, eroding the weakened rock until the concrete collapsed into the forming sinkhole. Which means that now running water can directly erode the bedrock, causing more damage (this possible explanation can however only be confirmed by a direct investigation of the exposed rocks).

Metamorphic rocks often cause engineering problems, as such rocks are often folded, resulting in tectonized/fractured areas in an otherwise stable rock mass. Also, the particular structure (the geological correct term is texture) of such rocks poses a problem. Metamorphic foliation forms when elongated or plate-shaped minerals (like micas) are forced by tectonic pressure into a same alignment. Between the minerals the parallel surfaces of the foliation form weak zones, prone to break. If such surfaces are tilted entire packets of rock can easily slip and be washed away by water.

With the emergency spillway the problem is similar, even if the erosion mechanism is not quite the same. The ground around the weir consists of rammed earth (soil consolidated with heavy construction machinery), but the ground of the emergency spillway consists of backfilled soil. This is a cheap and effective method to build dams, but it's also prone to erosion by fast flowing water, especially if the soil becomes soaked with it. Thus, the running water of the spillover is washing away soil, earth and rocks, forming deep gullies. The erosion front is creeping upslope as water flows down the slope.

The great problem now is that neither of the spillways can be used to control the water level in the lake without increasing erosion and damage in one of the spillways. During this storm, using the spillways as much as possible while trying to limit the discharge as much as necessary to slow down the ongoing erosion, the lake level was lowered by 8 feet a day and areas downhill the dam were evacuated as a precautionary measure.

If only the internet had been around at the time the Oroville Dam had been built. Them stupid engineers coulda just came on the fire and asked ol' Crossfire which way is up.

thank you for that admission.

Sycamore

If you're suggesting that the crowd of buffoons that put their "stamps' on the pathetic, miserable piles of schiddt that their work represented when that abortion was commissioned, you're dead right.

GTC

I see what you did there.

I'd venture that a rapid loss of the record snowpacks ( say by WARM rains) are going to verify the bolded.

The question of the day being, can the gates / turbine inlets at the dam,cranked wide open, in synch with the main spillway weirs keep the level of that lake BELOW the level of the headwall that comprises the auxilliary spilloff area. I call that a spilloff area cuz' calling it a "spillway" is a phoucin' joke,....and has been a source of confusion in defining WTH is going on up there from the get go.

GTC

Musta' been bothering you no end.
Hope you're sleeping better now.

Now tell us that you've got the BEST handle on what's gone on over there, and go back to sticking pins in your Ronald Reagan doll.



GTC

Evacuation is changed to a warning -- down from an order

They can go home

Crossfire,

I have read they had to shut the flow off through the turbines because the debris and flow down the main spillway has reversed the the flow in the river below the dam and the generators will be damaged because the water cant flow out?

Not sure if this is true and I have no knowledge about such things, just passing on what I read.

This is Higbeans back yard maybe he has more and better info?

Definitely wonder WTF will happen. This is plenty bad enough already - don't need to go full-on third World. Getting very little confidence from the bags of pebbles in the wake...

I would like to point out, AS AN ASIDE, that I have a KOM Railroader hat...

Given what that last post regarding the geo-morphology of the "bedrock" posits,....IF that lake starts running over that spill wall, bags of pebbles aren't gonna' mean jack diddly schidt, and we'll likely see a very bad situation.

Unseasonably cold and DRY weather would be welcomed.

GTC

This evening I finally returned to my friend's home that I've been staying with for the last two months. I'm currently about a mile away from the Feather River in Gridley California.

SCARY SCHIT !!!

Especially since my buddy's wife works for the DFG and has friends that work for the DWR. There's a whole nother story about what occurred that hasn't been told ... yet.

FWIW, it was psycho getting out of here on Sunday.

WOW - Tell us something juicy!

And the "whole nother story" is what ?

Basically, more damage that what's being reported and how close to the schit being spattered all over N Ca it really was.

I heard things today that made my skin crawl.

That's all I have to say about that.

Was it Masons?

Russians...

Thanks, Forrest!