Dam Trouble

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WBraun

climber
Feb 14, 2017 - 05:24pm PT
You guys are gonna scare those poor people living below the dam with all this talk of earthquakes and sh!t going wrong .......
Winemaker

Sport climber
Yakima, WA
Feb 14, 2017 - 05:36pm PT
August, I understand what you are saying about losing the emergency spillway; that is not a dam collapse. The question is, though, if the emergency spillway collapsed, would the erosion from the draining lake just keeping eating into the hillside? My understanding is the concrete emergency spillway is built on top of soil, hence the concern when erosion was evident at the base of the emergency spillway. If the concrete went, what then? How far to bedrock? Would that erosion lead to total failure of the hillside?
healyje

Trad climber
Portland, Oregon
Feb 14, 2017 - 06:03pm PT
You guys are gonna scare those poor people living below the dam with all this talk of earthquakes and sh!t going wrong .......

Too late, and they should be scared.
Kalimon

Social climber
Ridgway, CO
Feb 14, 2017 - 06:34pm PT
Thanks for all the great geology lessons t_tradster!

Thanks everyone for all the other quality images and input, too.

The subsurface composition, combined with the extreme forces at work above, lead to some disconcerting realizations. A dicey situation at best: extreme hydrologic conditions, combined with potentially poor design and inferior workmanship . . . recipe for disaster.

Bless the folks downstream.
john hansen

climber
Feb 14, 2017 - 07:45pm PT
Here is a grab I did from Google earth. Not sure how to link the site directly , but I am sure many of you use it.

If you drag around your mouse it will show the elevation at any given point, of course it does not work on this pic.
If you go to the top of the emergency spillway it reads 901 feet , so very accurate.

If you go along the western, (left) side of the parking lot it rises from the bottom where the road intersection is, at about 905 ft to the upper left corner where it is not much higher at all, 908 or so. There is a short section between that corner between the parking lot and the lake that goes up to 923.

I may revise some of these numbers when I look back at it but I don't think it is more then 1/4 mile from the lake to where it falls down past the end of the road to 875 pretty quickly.






So my idea would be to dig a channel right up that road and the west side of that lot , and thru that one section that is a little higher by the lake (think road cut).

It they went down 15 feet that would be to 890. It would not have to be that big of an opening as it would erode depending on the the amount of
water. Even down to 899 it could prevent over topping the emergency spillway.

en.I am certain they must have geological reports that show the underlying formations and how much erosion might happ

They could also leave 40 feet of undisturbed ground on the lake side, and only finish it at the last resort to keep the the other spillway being over topped.


I know this could cause lots of debris and mud but this is one of those years when there is so much water to flush everything out. I think that hillside would hold in the end.


Just throwing it out there ,,



I think that would be better than many thousands of peoples homes wiped out if that 30 foot wall failed.

Check out Google Earth and let me know what you think.
Winemaker

Sport climber
Yakima, WA
Feb 14, 2017 - 09:08pm PT
I think you'd be totally f*#ked, not knowing what the soil/rock was under there. What's to stop it from just eroding until the lake empties?
john hansen

climber
Feb 14, 2017 - 09:45pm PT
Yes that could be true but it could still remain an option.

And as I said above there are geographical maps for this area


EDIT:


DMT

LOL,,
clinker

Trad climber
Santa Cruz, California
Feb 15, 2017 - 12:52am PT
Ed Hartouni

Trad climber
Livermore, CA
Feb 15, 2017 - 12:58am PT
if you want to explore the geology...

http://mrdata.usgs.gov/geology/state/state.php?state=CA

here in Google Earth (download the kml file)
you can see the mapped faults too!
neebee

Social climber
calif/texas
Feb 15, 2017 - 01:29am PT
hey there say, tuolumne_tradster, and DMT, and all...

as to this:
[quote]The reason I bring this up is that many geophysicists & seismologists suspect that this earthquake was the result of reservoir-induced seismicity...namely the rapid filling of the nearby Zipingpu Dam on the Min River triggered this large earthquake. Dams & reservoirs are not just passive objects that may be vulnerable to failure from a nearby earthquake...they actually induce earthquakes, if the filling of the reservoir is not managed properly.
http://science.sciencemag.org/content/323/5912/322.full[/quote]

that is what i was wondering about, or,
anything similar, either as to the dam area,
or, really (with my limited knowledge) just in general,
as to the conditions 'down under' from drought, rapid
change to soak, etc...


say, ed, main reason, too, that i wonder:
IS all those faults... (you know, if more things
trigger them, as to the moving and slipping, etc,
within, or around them, than we REALLY know) ... oh my...


say, ed...thanks for the share, too...

let's hope and pray, all stays well, in calif...
our beloved calif, land of so many beautiful creations
and scenic views of them...

wow, LINK to the color chart, that
GOES to ed's colored map up there...

https://mrdata.usgs.gov/catalog/lithclass-color.php
neebee

Social climber
calif/texas
Feb 15, 2017 - 01:38am PT
hey there say, ed... man oh man, THIS is really great...

i just looked at texas, and michigan, ...

:O


the various rocks, in the areas, even JUST
within each state, etc is really
something to see, :O
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Feb 15, 2017 - 08:31am PT
This article in Forbes magazine yesterday by David Bressan, a self-proclaimed freelance geologist who works mainly on permafrost in the Eastern Alps...


http://www.forbes.com/sites/davidbressan/2017/02/14/some-geological-observations-on-the-oroville-dam/#4f27830a1925
cleo

Social climber
wherever you go, there you are
Feb 15, 2017 - 08:58am PT
My 2-cents?

DWR rejected the idea of armoring the Emergency Spillway on the grounds that "it's expensive and we're never going to use it - we have a giant regular spillway capable of 350,000 cfs." Even the letter from the Enviromental Groups note the the Emergency Spillway was supposed to be a "temporary" structure until Lake Marysville got built (it never got built).

So, that mindset made them ignore the Geology.

I'm going to be generous here and say that the problem with the REGULAR spillway was probably invisible - a small hole in the soil/rock that developed underneath during 4 years of drought and/or saturated hillslope runoff this year. Maybe only detectable with geophysics or drilling holes. The regular spillway probably hasn't been loaded in 4-5 years - and then it gets loaded, the concrete is unsupported, it starts to crack, water gets in, erosion accelerates, the spillway collapses.

The first day of testing DWR did scale back the flows to see what would happen, and there WAS some erosion creeping uphill... which is bad. So they made the decision to baby the regular spillway to limit uphill erosion, and in the meantime the reservoir filled. The inflow predictions weren't bad - they were a little off, but generally good... the operators just made the decision to run the reservoir up to the rim (and then over a little) to protect the regular spillway.

So the regular spillway ALSO failed due to Geology (I think...)

The operators of the dam may not have realized how vulnerable the Emergency Spillway was (complaints were lodged 7-12 years ago - there's turnover at DWR) After all, it was "supposed to" handle 10' of water over the crest (that's a lot!). But nobody really thought about whether the rock/soil downstream could handle that much water, which obviously it cannot. This is a design failure more than an operational failure.

SO... more geology required in CA civil engineering code and licensure! That's my recommendation!
neebee

Social climber
calif/texas
Feb 15, 2017 - 09:08am PT
hey there say, cleo... wow, thanks for the very good share, here...


say, thread drift, did you get your very late christmas card?
i sent it to your folks, first, but after it came back,
i FOUND an evelope with address? for when you came back into
the country, :)

hope you did!
you are NOT forgotten, :)

say, all... love the geo info, :)

tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Feb 15, 2017 - 09:16am PT
SO... more geology required in CA civil engineering code and licensure! That's my recommendation!
Couldn't agree more with that statement :-)

Here's some more info about the regional tectonic setting...the Oroville dam is located in the Sierra foothills metamorphic belt between two major regional faults, the Bear Mountain and Melones fault zones as shown on this tectonic map of California (in the area designated with horizontal stripes) described as Oceanic &/or island-arc terrane, largely melange. Melange is a geologic term indicating a rock composed primarily of a shale or mud matrix that contains "exotic" blocks (volkswagon to city block in scale) of mainly metamorphic rocks. These rocks generally originate in deep oceanic trenches associated with subduction zones.


Geology and tectonic evolution of the Bear Mountains Fault Zone, Foothills Terrane, central Sierra Nevada, California
Article in Tectonics 10(5):995-1006 · October 1991
DOI: 10.1029/91TC00862
Robert B Miller and Scott R Peterson

Abstract
The Late Jurassic-Early Cretaceous Bear Mountains fault zone (BMFZ) is the westernmost strand of the Foothills fault system in the Western Metamorphic belt of the Sierra Nevada. The tectonic significance of this 300-km-long fault zone has been downplayed in the past, but we contend that it is a major discontinuity within the Foothills terrane. The BMFZ is an ˜ 5-km-wide shear zone consisting of slate-metagraywacke-matrix melange that experienced intense polyphase deformation and metamorphism. Small-scale structures indicate reverse slip along most of the extent of this steeply east dipping shear zone. A host of lithologically diverse tectonic blocks are enclosed in the BMFZ. Blocks of sandstone, metavolcanic rocks, and plutonic rocks of intermediate composition have counterparts in the adjacent eastern and western zones of the Foothills terrane, whereas other block types are exotic. Exotic blocks include ultramafites that locally contain pods of gabbro, garnet amphibolite, greenschist, sedimentary breccia, and volcaniclastic rocks. The breccia is composed primarily of clasts of amphibolite and minor garnet-bearing impure quartzite (metachert?); it probably accumulated at the base of fault scarps. The exotic blocks comprise a broadly ophiolitic assemblage similar to that inferred to form basement to the Foothills terrane, and they record a deformation prior to incorporation in the slate-metagraywacke matrix. Amphibolite blocks and quartzite preserved as clasts within the breccia probably were deformed during overthrusting of oceanic lithosphere in a setting similar to that beneath the Tuolumne ophiolite east of the BMFZ. The presence of exotic blocks implies large-scale mixing and large displacements in the BMFZ, as do differences in stratigraphy across the fault zone. Metamorphic grade does not vary significantly across the BMFZ, however, suggesting that dip slip did not exceed several tens of kilometers if the fault zone originally dipped gently eastward as we propose. There is no direct evidence for major strike slip along the BMFZ as has been proposed by others; any such slip must have occurred before the reverse-slip related structures of the zone. We thus interpret the BMFZ as an intra-arc reverse fault of moderate to large displacement, with possible earlier strike slip, that incorporates ophiolitic basement showing an older, complicated history.

My understanding is that the fault lines shown on the map that Ed Hartouni posted ^^^ located to the west of the Oroville dam are segments of the Bear Mountain Fault Zone. This fault appears on the geologic map that I posed ^^^ also. If you look at the map that I posted ^^^ RE the Smartville Ophiolite you can see that there are ultramaphic rocks associated with the Melones fault zone, these are largely Serpentine. Needless to say, these rocks have come a long way from where they originated to where they are today.
Ed Hartouni

Trad climber
Livermore, CA
Feb 15, 2017 - 09:18am PT
In the run-up to the emergency spillway overflow, dam and DWR officials publicly vacillated about whether to use it or not.

not sure this is correct. The flood control rule book limits the flow that is allowed from the dam downstream.

the charts that they use as the rule to how much flood control capacity is required averages the precipitation over the previous 6 weeks.

I haven't done all the numbers, but it is possible that last week's intense storm was outside of the planning basis for those rules (which haven't been updated since the dam was first constructed, and is based on the knowledge of California climate in the then recorded history).


you can get the flows, etc, from this site:
http://www.spk-wc.usace.army.mil/reports/archives.html


I haven't gone back and calculated the release the rules required...
Reilly

Mountain climber
The Other Monrovia- CA
Feb 15, 2017 - 09:26am PT
"This is an aggressive proactive attack to address the erosion," said Bill Croyle, acting director of the state Dept of Water Resources.

Proactive? Really? Spoken like a true bureaucrat, sir.
John M

climber
Feb 15, 2017 - 09:46am PT
Obviously they were loathe to use it even then.

They had no need to use it as the main spillway was not damaged at that time and was perfectly capable of handling those flows. Everything changed when the main spillway became damaged.

Edit: Everything changed again when they discovered that the emergency/auxillary spillway was incapable of doing its job. Should they have known that it was poorly designed? I believe so, but then I am no expert. but even a none expert can tell you that compacted soil erodes fairly quickly with water. As far as heads rolling. There is a good chance that the people in charge back when they were sued over this are now retired. So whose head should roll? People inherit messes.
cleo

Social climber
wherever you go, there you are
Feb 15, 2017 - 10:34am PT
HELLO NEEBEE!

Yes, I got your card, thank you! I've been meaning to respond!

cleo

Social climber
wherever you go, there you are
Feb 15, 2017 - 10:37am PT
I see the geology maps - I don't find them all that helpful in this case. I'd love to see a site investigation report from the construction.

We went out to the site and there was more than one lithology - it ranged from hard metamorphic (meta-volcanic, I guess ... looked metamorphic from across the river) to softer semi-consolidated reddish rock - maybe a pyroclastic tuff with hillslope colluvium. In climbing terms, there was, Choss, Not Choss, and Soil at the site. The Choss and Soil are highly erodible!
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