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cleo
Social climber
wherever you go, there you are
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Feb 15, 2017 - 10:38am PT
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I'm really curious to know if the regular spillway is experiencing significant erosion uphill. Back to twitter for the latest photos!
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guyman
Social climber
Moorpark, CA.
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Feb 15, 2017 - 10:42am PT
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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.
How about starting from the TOP down.... work your way down to somebody who is competent, put them in control.
If retired.... how about a pension freeze/reduction...
that's the major problem with all this sh#t at the state level, the motto is "I will be retired when the mess hits the blades"
:>)
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TLP
climber
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Feb 15, 2017 - 10:57am PT
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"...when they discovered..." is BS. It was obvious 10 or 12 years ago, even to non-engineers, that the emergency spillway hillside needed to be armored in order to be able to withstand any significant flows overtopping it. Written comments to this effect were made during relicensing. It is certain that anyone with the slightest bit of engineering background, or just an iota of common sense, involved in the relicensing, knew that this was true. It's just as certain that the main customers' (for example, LA Metro. Water District's) desire to avoid paying for this work is the reason it wasn't done. Everyone, including MWD, certainly knew the emergency spillway wasn't viable, but probably figured that inflows would never be big enough, and/or that the main spillway would never suffer any issues, so the lake would never overtop.
It's a funny name, emergency spillway, which we now know doesn't mean "will be overtopped in an emergency" but instead, "if water ever goes over this it'll be a major emergency."
Cleo is 100 percent right on about choss, non-choss, and soil at the site. There must be a nice piece of non-choss that's making that spectacular rooster tail in the breached main spillway, the issue is, can it headcut back up to the spillway structure. And if it's headcutting, which would be the bigger flood: let the main spillway structure fail at the lip, or close it before, and let the emergency one fail. In other words, where's the low point of competent rock between the dam and the hillside the emergency spillway ties into. That's an operations decision no one is going to want to make if the spillway keeps headcutting up. It doesn't seem to be doing that, but it hasn't had 100,000 cfs or more going down it for all that long.
1997 flood was January 2, and is the highest flood of record on many northern/central California rivers and tributaries. Some of them (Merced for example), had similar flood levels on January 3.
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John M
climber
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Feb 15, 2017 - 11:00am PT
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Yes.. the 97 flood started Dec 31st 1996, and went to the 5th.
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Ksolem
Trad climber
Monrovia, California
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Feb 15, 2017 - 11:00am PT
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"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.
Reilly, of course locking the barn after the horses are out is pro-active. Since they cannot get back in, they cannot escape again.
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Cragar
climber
MSLA - MT
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Feb 15, 2017 - 11:06am PT
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Cleo, keep them geo-explanations coming; oh, pics would be coo too!
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guyman
Social climber
Moorpark, CA.
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Feb 15, 2017 - 11:07am PT
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What if we get another MARCH MIRACLE like the one in 1991.... a whole years worth of rain in 30 days.
What then batman?
It would seem to me that SAFETY would be the number one concern.
screw the water.
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Feb 15, 2017 - 11:09am PT
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Lots of excellent info and photos here
Oroville Dam Main Spillway Waterfall Erosion Watch thread...
Since the eroson of the main spillway is the key risk now water levels are under control, I've created this thread to keep track of any changes in the erosion at the "waterfall" location. Inevitably there will be some "head cutting" and the erosion will the move up the hill. However it seems to have stopped since Feb 10, and the hope is that it is now stable with the spillway spilling over a rock-bedded location.
https://www.metabunk.org/oroville-dam-main-spillway-waterfall-erosion-watch.t8402/
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survival
Big Wall climber
Terrapin Station
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Feb 15, 2017 - 11:14am PT
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This morning a CalFire guy showed me pictures of his brother in 1986, standing on the 49 guardrail, above the American confluence, coming down from Cool.
The 49 bridge and the no-hands bridge were completely underwater, by a long ways. Unrecognizeable.
Wow....
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skcreidc
Social climber
SD, CA
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Feb 15, 2017 - 11:18am PT
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Some 20% of all dam failures are due to piping (internal erosion caused by seepage). Spillway weirs are one of the structures that fail via piping. This type of failure typically has nothing directly (or very little) to do with geology, but rather the slow constant water pressure, or head, placed on an earthen construction holding back water. The actual Oroville dam is a zoned earthen construction and should be resistant to this kind of hydrologic attack. But the spillway weir is another story and may be constructed differently. At least so far I have not found any details on the spillway construction. This is just me bullshitting at this time and the people working on the problem should have the construction specs at their fingertips. But to me, the potential for it to be a piping problem based on placement is high.
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John M
climber
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Feb 15, 2017 - 11:25am PT
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But to me, the potential for it to be a piping problem based on placement is high.
If it were a pipping problem in the ESW, then wouldn't there be water running, seeping after they stopped overflowing it?
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TLP
climber
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Feb 15, 2017 - 11:29am PT
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Great link, tradster! Very good photos and text, about as reassuring as we're likely to see. It's very sobering to see the teeny tiny size of the rock bags they're placing, one slowly by one, in the context of the vast expanse of just plain soil and the new Oroville Falls (which must leap a good ways up the list of tallest cascades/waterfalls in Calif.).
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neebee
Social climber
calif/texas
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Feb 15, 2017 - 11:34am PT
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hey there say, great cleo!
came back fast, got to run now... busy busy busy, :))
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G_Gnome
Trad climber
Cali
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Feb 15, 2017 - 11:37am PT
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And what happens when Lake Shasta overflows later this month. Will there be similar problems showing up there?
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skcreidc
Social climber
SD, CA
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Feb 15, 2017 - 11:54am PT
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John M. Yes, if there is no seepage then it is probably just erosion of the spillway itself, perhaps exacerbated by differential settling. What few photos I have seen, it is hard to tell if there is any seepage as it could stay underneath the concrete apron following the contour of topography. Scary thought is that over the past week I have been getting what little updates on the dam I get here, lol. So I have missed a lot of potentially pertinent information to be sure.
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Feb 15, 2017 - 12:21pm PT
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to Cleo's point, the geologic maps posted ^^^ are useful for understanding the regional scale distribution of geologic units and structures. This photo shows the scale that is relevant to the
erosion of the main & emergency spillways. As you can see, there is a great deal of variability in the distribution of soil, weathered, and unweathered bedrock. Rather than being a uniform mass of solid material, the bedrock is highly fractured and sheared...more like Mt Dana and Mt Morrison than Fairview dome ;-)
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healyje
Trad climber
Portland, Oregon
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Feb 15, 2017 - 12:34pm PT
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I think it was again a mistake not to take both spillways back down to rock and build them back up. Way more expensive though.
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skcreidc
Social climber
SD, CA
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Feb 15, 2017 - 01:24pm PT
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TT, unfortunately that scale mapping does not do us much good for any real eval, but you probably already know this. At the scene evaluation is critical, and we need to trust those at the scene doing the eval. That scale mapping is only good as a cursory start to an evaluation. There should be core and borehole samples as well logs from the initial investigation. I used to be a hard core hydrologist and geologist and traveled extensively over the years.
Not even knowing the site though, green schist is notorious for being unstable due to the inconsistency of secondary alteration and consolidation as well as fracturing.
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rick sumner
Trad climber
reno, nevada/ wasilla alaska
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Feb 15, 2017 - 02:08pm PT
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It's indisputable that the Dam is already in failure mode. The project was originally rushed along by papa Moonbeam with intentional or unintentional lack of adequate coring to determine the degree and extent of heavily fractured bedrock susceptible to erosion in the main and emergency spillway areas. Additionally, it seems, the 100 year rainfall/melt potential of California's long term climate was ignored. This dam should have been pared with another upstream to accommodate the possible fill potential, without resorting to emergency releases,
during a 100 year event. Any study this design was based on is phony science ( much like current catastrophic anthropogenic global warming)
that is verging on a capital punishment level crime. The only thing separating downstream communities from wide spread losses of property and life is luck at this point. If you're not a heathen say a prayer.
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