Emergency: California’s Oroville Dam Spillway Near Failure, Evacuations Ordered

Breitbart ^ | Feb 12, 2017 | Joel B. Pollak1

[EarthResearcher333]

"There appear to be 3 overarching design concepts which have been proposed for rebuilding the main spillway.."

Hi jpal, Query: Where have these 3 design concepts been proposed? Are these early designs that have been released by DWR engineers? Or are they from discussions?

Your insight in the description of the situation is accurate to the engineering challenges they face. I would add that there are additional dimensions to the choices & difficult tradeoffs that are faced. If you were to create a cross-matrix array of the interdependencies of design, funding, politics, time crunch, and the "hand of God via nature - weather", you would end up with a dynamic project that must be adaptable.

On one hand, they must protect the public from catastrophic event(s) - thus the need to emergency repair & armor the Emergency Spillway as there is an unknown to the integrity of the upper main spillway's health.

On the other hand, they must plan for the ultimate restoration to adequate safety factor ratings to the Maximum Probable Flood levels. How they get there from now to the ultimate restoration almost assuredly requires flexibility in interim options.

I wouldn't be at all surprised if an option develops where a "flip" is used to a secondary lower spillway where the secondary lower spillway is built to dissipate the "capture" of the lift and transport it to another form of a dissipation block system @ the Feather river.

In any case, keep the wheels turning... we'll see what is going to be proposed soon. Let's hope the hand of God in Nature will be amenable (for the sake of many below the dam).

and Keep posting...

[alfa6]

A question if you please.

It would appear that the upper portion of the spill way is compromised, most likely fatally, but the DWR is pretty much stuck with it for the foreseeable future.

I have seen on highway overpasses here in KC where the DOT has placed an epoxy coating on the roadway. This coating has been in place for at least 5 years and seems to be holding up rather well. I would guess that this process could be done rather quickly and given the massive amounts of money already spent fairly cheaply:-)

In your opinion do you think this would work as a sealant to stop/reduce water infiltration through the spill way?

Regards

alfa6 ;>}

[EarthResearcher333]

In your opinion do you think this would work as a sealant to stop/reduce water infiltration through the spill way?

High Tech materials are available such as super-low-viscosity (SLV) epoxy for "micro crack healer-sealer" including expandable chemical urethane to stop multiple leak branching sources. These materials have been used exactly for modern dam spillway repairs by reputable & experienced concrete specialization companies.

Oroville's spillway design poses many challenges*. They don't even know why the waterflow continues to discharge for a while after the gates are closed. It's clear that the original construction placed a layer of washable material -such as compacted aggregate & now revealed "clay" in spots - between the bedrock (or less than bedrock) and the slabs. Voiding formed and now there is discussion of "channel flows" (or "piping" in the engineering term) nearly everywhere (to some degree). Look at the "void seam" before they shotcreted the damaged upper spillway.

There is evidence that the "voiding" combined with the "thinning" of the slabs by the drain piping design is causing a flexure of the slabs** when the spillway is used (at a decent flow). This could cause all of the patching at the cracked drain profiles to re-crack.

So the question becomes: (IF the MS needs a superior sealing state to reduce problematic developments) - What are the "flexing" dynamics of the spillway? This will drive the answer to the effectiveness of a technological materials application choice.

btw- there are some amazing epoxies available today. One type that I favor is an aerospace grade epoxy that is used to bond joints in high stress flexing and aircraft grade reliability performance requirements in copter blades. It is expensive & is made by 3M.

*Drains emplaced "upward into the slabs" severely "thinned" the concrete slabs. The slabs severely cracked above nearly every single drain line run on the entire spillway. The 50 yr old spillway design does not have seam "water stops". The spillway concrete pour was emplaced upon a washable compacted gravel bed. Thus large crack volume + seams area per slab drives a pressurized waterflow from spillway operation.

**More flexure means continued failure of concrete surface patching, leading to re-cracking of the patch in addition to surface stresses exposing the seams to spontaneous spalling ("chipping").

[meyer]

I’m far from being an expert in such things, but I think that it’s possible that something of that nature could be used. One of the things that has to occur is that the individual slabs of concrete have to be able to slide in a way that allows contraction/expansion of the concrete based on heating and cooling (not to mention the varying weight of water depending on the amount of spilling taking place). The joints allow this, but might also be allowing some leakage as a result.

I’m not sure that a perfect seal is desired, though, unless the sealing material had enough flexibility to allow for some movement. So maybe perfect isn’t quite the goal, but reduction of leakage and a close eye on outflows through the side drains is more in order.

So there’s my non-answer/musings. :)

[KC Burke]

The spillway upper section just has to last until mid June. If they can get another 80 days out of it until Spring melt and rains are peaked then they can replace the whole dam thing. (That was a bad pun wasn’t it? — blame the Jayhawks)

I don’t think they want new chem coatings in the feather or to spend money for momentary band aids.

[KC Burke]

The spillway upper section just has to last until mid June. If they can get another 80 days out of it until Spring melt and rains are peaked then they can replace the whole dam thing. (That was a bad pun wasn’t it? — blame the Jayhawks)

I don’t think they want new chem coatings in the feather or to spend money for momentary band aids.

[alfa6]

Thanks gents for the thoughtful replies.

I can’t believe I forgot about the expansion issue, will have to give my self a dope smack for that one:-)

Off to work I must go:-(

Regards

alfa6 ;>}

[mad_as_he$$]

Don’t overlook option 4 - decommission the entire system.

“....both spillways to dissipate around 30 GW of power,”

Mind boggling.

[Repeal The 17th]

With that kind of power, and a Delorean,
we could go back in time and fix the spillway
before it became a problem.

[EternalHope]

One additional consideration: the “probable maximum flood” design criteria for both spillways is more than 600,000 CFS. With 600 feet of head, this would require both spillways to dissipate around 30 GW of power, approximately equal to the instantaneous power consumption of the entire state of California.

It seems unrealistic to expect this amount of power to be dissipated in such a small area without some significant collateral damage.

I would take your final statement a step futher: I am CERTAIN most people vastly underestimate just how hard it is to dissipate that much energy.

As an example, and just for starters, you run a high risk of creating your own weather from the enormous amount of spray you are certain to generate. With that much energy to dissipate, it seems highly likely the spray will be energetic enough to generate lightning.

I'll even go so far as to guess this question was never even asked when the dam was designed. I'm not a civil engineer, but it's easy to see how they may not think of it now either.

REAL WORLD EXAMPLE: Way back in ancient history (only slightly before my time), a volcano erupted in Iceland. The lava flow threatened a developed area. Some genius decided the lava could be stopped by dropping water on it.

The Air Force loaded up some aircraft with water and they took off for Iceland.

Then someone spent a few minutes calculating how much energy would be released if all that water vaporized (it would have). The energy release would have been equivalent to a nuclear bomb. Not released in a single split second, but fast enough to be devastating none the less.

The planes were called back while in flight. I learned this from one of my engineering profs while I was a cadet at the Air Force Academy. I have no idea if it ever made it into the news, but it certainly made a permanent impression on me.

[mad_as_he$$]

+1.

https://www.youtube.com/watch?v=4BVQri3aLfg

[mad_as_he$$]

That is the reason I found the small scale flow tests from the design phase so interesting and concerning at the same time. Trying to narrow the flow after the water is released is just poor fluid(s) reality and against common physics principles. If any thing the spillway should get wider. AND who the heck decided to put the drop off in the spillway. It should of been a straight line from the gates to the bottom. Probably was chosen to save moving some additional earth. Well they wound up moving it anyway along with 900,000 additional yards at 100+ times what it would of cost in 1967.

[KC Burke]

The dissipation blocks and the little flip at the end are meant to be energy dissipation features to try and impact the river less. There are even dams with a giant flip ski jumping spllway.

The dam height here means the spillway has to be long and energy generated is huge.

[mad_as_he$$]

Understood. I was specifically referring to the test designs, on the flow model bed, where there were variations of wings or funnel shapes just after the spillway gates. The hump has always bothered since the first time I stood at the base and looked up the spillway in 1982. Very few if any dams in the US have a spillway that long. Extra care should of been exercised in the design.

[Repeal The 17th]

They appear to be slowly throttling back the flow:
http://cdec.water.ca.gov/cgi-progs/queryF?ORO
Hopefully, tomorrow we will be able to see
the upper portion of the spillway held in place,
and the debris in the river is minimal.
(fingers crossed)

[EarthResearcher333]

2014/2015 Dam Inspection Reports: "Long Standing..Wet Area" - midslope dam backside seepage (being ignored?)

Just an FYI - A persistent, long existing, seepage wet area on the midslope area backside of the main earthen dam is noted in the 2014 & 2015 Oroville Dam Inspection Reports. A photograph of this location was included in the 2015 report where the inspector placed a red arrow in the pic to denote the green vegetation from the wet area. The safety Inspector recommended that this should be investigated**. Recommendations included taking measures, if needed, "to ensure the long term stability of the slope". The picture description stated that this was a "long standing…wet area". A prior June 2014 Inspection report also noted this "wet area" and that "Staff should continue to monitor the mid-slope seepage at the left side of the downstream slope". It continues: "A means of monitoring the extent of the seepage area should be implemented".

What would seem odd is that the same recommendations are made in 2014 AND 2015, but with no apparent change in action. You would expect that the 2015 report would include the status of the implementation of "monitoring" as recommended in the 2014 report. So why wasn't any action taken? Why is the 2015 report stating "this should be investigated"?

Then 2016 rolls along with the drought and the left side of the dam "seepage" area has dried up. Yet no discussion of the recommendations from 2014 and 2015. The 2016 report just states "The long standing seepage area at mid-slope on the left side of the dam has dried up due to the prolonged drought." i.e. infers that this issue has been sidelined as it went away due to the drought (and low water levels eh?). Let's hope that this issue doesn't recur in the midst of the Spillway crisis now that the water levels in the dam are above "mid-slope".

**note: Oroville dam uses a thick shell barrier of an inclined compacted clay core as the water barrier of the main dam. Any presence of water seepage or "wet areas" on the downstream face of the dam could infer a leakage or crack within this water barrier.

Oroville Dam Inspection Report June 2014 - mid-slope seepage & monitoring the "extent"

Oroville Dam Inspection Report 2015 - Wet Area Mid-slope on Dam (Picture 4)

Oroville Dam Inspection Report 2016 - seepage area dried out from prolonged drought

CA Division of Safety of Dams Inspection Report 2014 - Recommendation to implement a method to "monitor the mid-slope seepage" on the backside mid-slope of Oroville's earthen dam

CA Division of Safety of Dams Inspection Report 2015 - Stronger Recommendation to "investigate" wet area "to ensure the long term stability of the slope"

CA Division of Safety of Dams Inspection Report 2015 - Inspector picture with red arrow pointing to wet area that "should be investigated"…"to ensure the long term stability of the slope"

CA Division of Safety of Dams Inspection Report 2016 - "*never mind*"… the wet spot has dried up due to the prolonged drought…!?!

[Repeal The 17th]

Hard to orient myself in those pictures.
Is this in the main dam structure?
(not near the spillway where you noted the wet spots in the hydro-seeding)

[abb]

http://www.sacbee.com/news/state/california/water-and-drought/article141054803.html

March 27, 2017 12:37 PM
Oroville Dam spillway shut down again as state officials work on long-term plan

By Dale Kasler and Ryan Sabalow

dkasler@sacbee.com
OROVILLE

The operators of Oroville Dam acknowledged Monday they might not be able to permanently repair the dam’s battered main spillway in time for the next rainy season, but said they’re confident the fractured structure will be usable.

Engineers expect to have this summer’s repair plans largely in place by early next week for the concrete spillway, said Bill Croyle, the acting director of the state Department of Water Resources.

“If I have anything to say about it, we’ll have a spillway to use by Nov. 1,” Croyle said, referring to the expected start of the next rainy season. “Whether that’s a permanent or temporary structure, it hasn’t yet been decided.”

snip

Monday’s briefing also served to announce that the dam’s operators were again shutting off the water flowing down the spillway. The structure had been releasing water at about 40,000 cubic feet per second since March 17. The releases would be dialed back to zero by Monday night and could stay that way for the next 15 days.

Croyle said the shutoff will enable DWR crews to dredge more debris from the Feather River channel at the base of the spillway and make additional repairs to the dam’s hydroelectric power plant. The plant was shut off temporarily Monday as well, although Croyle said it was expected to resume releasing water Monday afternoon.

snip

[EarthResearcher333]

"Is this in the main dam structure?"

Yes. The views are of the backside of the big earthen dam. It's the last place you want to see water seepage & wet areas on an earthen dam.

[WildHighlander57]

Where is that in relation to the front of the dam?

It looks like the power substation is downslope on the right, so I think it’s on the front.

Bad news, if there’s seepage on the main dam itself.