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

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

[janetjanet998]

The California Department of Water Resources issued a sudden evacuation order shortly before 5 p.m. Sunday for residents near the Oroville Dam in northern California, warning that the dam’s emergency spillway would fail in the next 60 minutes.

The Oroville Dam is the highest in the nation.

[EarthResearcher333]

Oroville mayor lashes out over dam communications

-- clip: SACRAMENTO, Calif. (AP) — Oroville's mayor said Thursday she knew about cracks in the replacement spillway at the troubled dam nearby and is not concerned, but heaped criticism on state water officials for failing to communicate with her town.

Linda Dahlmeier said the Department of Water Resources should have proactively communicated that cracks were expected but has instead created a "firestorm" in a community that was rattled by sudden evacuation orders last February. Nearly 200,000 people were forced to flee when engineers feared that damaged spillways at Oroville Dam would unleash an uncontrolled wall of water that would inundate her town and others downstream. The crisis was averted.

...

Many residents of Oroville don't trust what they're hearing from the Department of Water Resources, she said, and officials in the agency's Sacramento headquarters have failed to address the concerns of people living in the shadow of the nation's tallest dam.

... "cracks in the hundreds"...

--- end clips more at link http://www.sfgate.com/news/article/Oroville-mayor-lashes-out-over-dam-communications-12396585.php

[KC Burke]

...that anchoring the slabs to the foundation beneath the spillway, a key design element intended to strengthen the overall structure, contributed to the cracking but doesn’t harm the integrity of the chute."

Shrinkage cracks and edge curling occurs in large slab segments supported by subgrade to one degree or another as a large slab cures and hardens. Cure cover retards the curing and helps avoid large cracks but does not eliminate the shrinkage forces.

Large amounts of horizontal reinforcement bond with the concrete as it cures and the deformations of the reinforcement surfaces make the concrete with reinforcement work as a composite material with tensions of shrinkage adding to the forces on the slab.

Now, you take that shrinking plate that is curing and shrinking on that sub-grade and you stitch-anchor it down to supposedly help keep it on the hillside and supposedly help it resist disassembly forces should it segment -- this is what was done with the anchoring bars. However, that pins the segments where it is trying to shrink horizontally at right angles to such anchorage.

The problem we are seeing of some shrinkage cracking is a factor of that sort of design attempt. The factor that would limit this occurrence is to further limit the dimensions of the slab segments and increase the frequency of jointing which has its own severe life-cycle problems of cleaning, and caulking which never last.

I would have preferred the thickness of the slab being sufficient to hold it in place as opposed to that anchorage system -- a difficult issue on this degree of slope -- but, I am just an old contractor -- this is a design issue.

[EternalHope]

Not a civil engineer, but I have to wonder if water in the cracks will shorten the life of the spillway. Freezing, corrosion of any rebar it reaches, etc.

To prevent or reduce this, perhaps some sort of sealant should be applied to the surface after the concrete has completely cured. It would have to be completely dry when applied, so I doubt it could be done until after the rainy season.

[EarthResearcher333]

The Key "Reveal" to this situation is what Peterson from Kiewit noted to sfgate:

"Adjusting the concrete mixture could reduce the number of cracks, Petersen said, but experts need to be careful not to reduce the concrete's strength."

Apparently, FERC is the one that discovered these cracks and then asked DWR to explain it. This begs the question of "why didn't DWR find it first?".

The concrete in question is the special mix "erosion resistant" concrete. By Peterson discussing an option of "adjusting the concrete mixture" reveals that there is some "tuning" that may have been in the design bedrock anchoring/settling assumptions.

OR - there were "unknown" "unknowns" regarding the geologic bedrock settling. Either way, it is truly a PR mess. The mayor is angry. The citizens are now alarmed. And it's possible that DWR may have "fumbled" this from a PR/communications standpoint.

Best to be open and up front early on, just as how the Corps handled the collapsed gate failure at Folsum Dam.

[Jim W N]

Predictable? DWR worried more about PR than doing the job right?

I’m not an engineer, but this whole thing smells like that.

[KC Burke]

I would add there is a stupid quote in your article clips in 4439.

University of California, Berkeley, civil engineering professor Robert Bea said cracking in high-strength reinforced concrete structures is never expected.

My entire life concrete specialists and sensible engineers have always said, "Reinforced Concrete cracks." It is always a question of how much, where limited, how controlled etc. Reinforced Concrete is not an homogenous material entirely uniform throughout.

I don't like the part where they are saying that they already are concerned about a funky Mix Design on the concrete. That shows me that there were questions and issues about this during design and mix approval. I never, never want to place a significant concrete placement where there is no "history" of performance of a specific mix design from the nearby plants with the selected aggregate source and mix. I had a competitor once who beat me out of a big runway job and that idiot used an aggregate sizing that had never been used from that quarry before in his runway mix. The runway failed and was out of service for over a year with millions in repairs.

Now all that being said, I would like to walk the spillway and look at it myself. Cracks are due to many issues. Shrink cracks, "D" Cracks, Plastic Cracks, "Y" Cracks, Sub-Grade swell or subsidence cracks, stress cracks, and on and on.

Most people do not understand that hairline cracks where you still have aggregate interlock are not a really significant issue in many types of horizontal surfaces. This pig is not very forgiving as we have previously found out.

[EarthResearcher333]

I have access to information that I cannot share publicly. There is more to this story and there are affirmations that confirm what was said (individual).

I must maintain confidentiality on this matter.

[The Westerner]

Not sure what you’re referring to in this reply?

Is there anyone at DWR who attempts to tell a straight story? Are the PR folks callous, inept or both?

[KC Burke]

The issue of an erosion resistant mix design being selected for usage caused me to speculate on the risks of special mix designs that might not have a succulent history with the exact aggregate, cement and mix equipment.

ER declined to speculate.

The 2/3 of the finished spillway being in place having cracks raises questions as to ownership management of the project that is currently at half a billion that California is planning to bleed out of the US tax payer.

[EarthResearcher333]

All I can say is that FERC was correct in their surprise and reasons for asking DWR for an explanation. One of the articles mentioned that DWR was planning on holding some community meetings due to the controversy or surprise of what the AP discovered in FERC to DWR communication letters (only gleaning info from the subject "cover letters" on FERC's database).

[EarthResearcher333]

Town Hall turns into "Screaming match" over Cracks

Article clips ------

Oroville Dam neighbors and downstream residents blasted California officials for claiming they should not worry about hundreds of cracks in the newly reconstructed dam spillway.

The California Department of Water Resources (DWR) public presentation to City of Oroville and downstream Feather River residents deteriorated into a screaming match after the state’s dam experts tried to reassure the community that there was nothing to see in the string of hairline cracks that have developed just weeks after finishing the $275 million first phase of rebuilding of the dam’s spillways.

Residents hammered the DWR with complaints, asking why they ought to believe the State of California after officials were not honest with the community regarding the breadth of safety problems that were known for almost a decade.

…

But the Sacramento Bee reported in late November that that cracks were first detected in September “when the first phase was nearing completion.” The Federal Energy Regulatory Commission (FERC), which has federal oversight over the California-owned dam, instructed DWR on October 2 to investigate “cracking of the erosion resistant concrete” and to recommend any further steps necessary to address infrastructure risks.

….

But KQED reported last week that Robert Bea, professor emeritus of civil engineering and founder of the respected UC Berkeley Center for Catastrophic Risk Management, stated: “Cracking in high-strength reinforced concrete structures is never to be expected.” He added that when large volumes of water cascade down the spillway at speeds approaching 90 miles per hour, even small cracks can increase stresses on concrete.

---- end clips more at link

Oroville Dam Neighbors Fear Hundreds of New Spillway Cracks

[EarthResearcher333]

DWR releases CEII "Crack" report - Shows full thickness Slab cracks - other extensive crack patterns - tried to fix in mix ratios during construction

New details & photographs are now coming out on the Oroville Spillway Cracks. These "cracks" are extensive and photos show that some go fully through the thickness of the slabs. (see report and photos)

Perhaps the most significant question, which becomes rhetorical, is "If you knew that it was going to crack as it did, why didn't you use epoxy coated rebar in the lower slab layer?". Simply answering this question is "have you stopped beating your wife" trap. Either DWR knew it was going to crack to the full slab thickness and DWR didn't consider the long term implications of corrosion of the lower rebar - OR - DWR didn't know it was going to crack through the full slab thickness and DWR believed they didn't have to use epoxy coated rebar in the lower layer.

Prof. Robert Bea has been unfairly criticized in other media. Yet the new report buttresses the concerns originally stated by Prof Bea. Massive Oil well structures, constructed of concrete, and within a saltwater environment, requires important specifications to insure a pure intolerance for cracking. These structures also have deal with anchorage stresses for lateral high storm conditions (seas) and including the footing stresses.

Some early youtube shots of the new spillway show water flowing up these cracks to the slab surface. This "water exposure" demonstrates that the slab to base concrete mating surface is resisting in flow routes to the nearest drain(s). Thus "corrosion" of the lower rebar is a given risk from the reported near 200 cracks (plus the unseen ones). This is highly unfortunate. (Rhetorical again ->) IF they were expecting these cracks, they should have used epoxy coated rebar in the lower slab layer as they did in the upper layer rebar (used green epoxy coated rebar in the upper layer).

Of note: Notice the use of uncertain terms in the report (i.e. "theory", "could have", "likely caused"..). These terms wouldn't be used IF DWR fully expected the cracking outcome if you listen to the recent explanations given to the public.

Newly classified CEII report released (with a noted full page or pages "attachment" redaction):

http://www.water.ca.gov/oroville-spillway/pdf/2017/20171102_DWR_TM_SRT-FCO-DOC-09_CEII%20Redacted_Att1.pdf

--- Article (link below) clips: (emphasis mine)

Brown wrote that most of the cracking was likely caused by the vast amount of restraints, including the underlying leveling concrete and slab anchors. That theory was supported by mapping which showed most of the cracks between anchors, he said. Thermal shrinkage could also have been a contributor, though not likely the main reason because the difference in temperature between the top and interior of concrete panels was negligible, according to the report.

Cracking could also have been a result of plastic shrinkage, “usually associated with the rapid loss of moisture caused by a combination of factors that include high air and concrete temperatures, low relative humidity, and high wind velocity at the surface of the concrete.”

In that case, what begins as shallow cracks can turn into deep cracks later, according to the American Concrete Institute, which Brown cited in the report. At the end of the memo, it states that the department would expand its investigation into the cracks and look into modifying the curing process or making changes to the concrete mix, such as using shrinkage-reducing admixtures, which Assistant Professor Feraidon Ataie, director of Chico State University’s concrete industry management program, suggested in a previous interview with this newspaper.

Professor Robert Bea with U.C. Berkeley’s Center for Catastrophic Risk management said on Monday he found two of the pictures, figures one and three in the report which show thin and long breaks in the concrete, significant and “very scary.”

“I hope no one will believe that this type of cracking — not the crazing at the surface of the concrete — is ‘to be expected,’” Bea wrote in an email. “I have helped design, construct, operate, and maintain some very large reinforced concrete structures. These structures had many more ‘restraints’ than the re-constructed spillway. Significant cracking was not tolerated. If found, it was immediately ‘fixed’ and then monitored to be sure that the ‘fix’ had been effective.”

A DWR spokesperson could not be reached for comment before the deadline for this story.

--- end clips more at link

Article: Oroville Dam: Formerly classified memo describing spillway cracks now public

http://www.chicoer.com/general-news/20171211/oroville-dam-formerly-classified-memo-describing-spillway-cracks-now-public

Newly released CEII doc by DWR - shows extent of areas of "cracking" - photo of new slab surface.

Newly released CEII doc by DWR: Full thickness Cracking in new slab - exposure risk to corrosion of unprotected lower rebar layer from upward penetrating water.

[abb]

This ain’t gonna end well.

[mad_as_he$$]

Whoa! I was expecting some surface checking.

[EarthResearcher333]

You found a key to the problem.... someone had a duty to QC the conditions in the midst of the construction. Here is the "revealing" critical line in the DWR report:

---------

Cracking could also have been a result of plastic shrinkage, “usually associated with the rapid loss of moisture caused by a combination of factors that include high air and concrete temperatures, low relative humidity, and high wind velocity at the surface of the concrete.”*

---------

*(exact weather patterns/extremes at Oroville during construction)

This official statement directly infers that QC DID NOT know these variables during construction (or was poorly monitoring them).

This was DWR's responsibility. The other responsibility was QC feed back to Kiewit on early problems. Then it was a combined responsibility to figure out the proper action(s) (Mix? QC? or too late by then?).

Other nagging question(s)... Why was it that FERC was the one to officially discover this cracking? (FERC immediately asked DWR to explain the cracks & have DWR explain why).

Why didn't DWR notify FERC first? Did DWR think it wasn't anything to worry about? (competency? miscommunications? PR concerns?).

DWR has another town hall coming up..... Like abb said "This aint going to end well".

[mad_as_he$$]

Very disturbing turn of events. The finger pointing on this will be epic.

I was actually rooting for DWR to pull this off successfully, in the interest of public safety.

[KC Burke]

Much of this is consistent with concerns I mentioned earlier. The critical items in my opinion are mix design specified and the amount of anchorage attachment to the rock or sub-base roller compacted substitute.

The one thing I want to comment on with these cracks being full slab is that to me it is LESS indicative of the ambient temperature / humidity curing issues due to slab thickness.

Most of us deal with slab or thicknesses that are much thinner, even in roadbed construction. This thickness acts as its own protection to inner and lower levels and the lack of dry granular sub-base also means that accelerated drying would have produced surface cracks only — not full thickness. To me that is the least important of the issues.

In August or the first of September, the time schedule should have been stopped and the cracking problem dealt with to the point of resolution. Now they cannot determine what to change until they restart next year. I am somewhat tickled that they cite the original cost when talking about the project when we all remember that they have already approved changes taking it to the 500 million dollar vicinity. Sort of a Freudian slip to cite the lower figure.

[EternalHope]

The location of the cracks raises another question that I have not seen addressed.

The rebar is presumably very solidly anchored in good rock. It is also well established that the area is geologically active.

An often overlooked fact is that solid rock can and does move. If it moves an easily detectable amount we can measure the energy released (an earthquake). But the ground can and does bend elastically as well. The movement is NOT necessarily uniform.

This may seem irrelevant, and most of the time it is. However we have just added enormous weight on a slope, and anchored that weight into the rock below. This weight could easily be enough to cause elastic deformation of the rock as it adjusts to the new conditions. On a steep slope with variation in the slope the load would not be uniform, and I would not expect the deformation to be uniform.

In most situations the weight would be added much more slowly, giving the rock more time to adjust. Movement would still occur, but the movement would be transferred only to the concrete that had already been poured. Subsequent layers would be affected by any movement that had occurred prior to when they were poured.

If this is happening I would expect the solidly anchored rebar to transmit minute differences in movement to the concrete. Since it was all done so quickly, it is easy to see how this movement would be transmitted through the entire thickness of the concrete.

Exacerbating the situation, in this case the concrete may not have enough time to fully cure. If there is minute differential movement in the base this would make it more vulnerable to cracking.

This is bound to seem far fetched to engineers who have vast experience in the field. However, this is certainly an unusual situation and that’s when the unexpected is most likely to occur.

For those of you who consider this possibility nuts, consider the location of the cracks. They are NOT over the rebar. If the cracks are caused solely by shrinkage of the concrete as it cures then they should be more evenly distributed. Something about the rebar must be affecting their location.

There is also a way to test this hypothesis. The slope of the spillway varies. If minute differences in movement of the rock the spillway is anchored into are a significant contributing factor, then you would also expect the distribution and size of the cracks to be correlated in some way with the slope of the spillway.

Final comment: Yes, I realize I may, in fact, be nuts. I am not a civil engineer. My first two degrees were in unrelated fields of engineering (mostly math) and I have only a tiny bit of hands on engineering experience. Worse, I’m so ancient I used a slide rule and analog computer all the way through my undergraduate years.

[Jim W N]

Can’t blame those residents. If I were living in Oroville or anywhere below this monstrous dam, I’d be screaming at these guys too.

[Jim W N]

Well, we know you can’t do the wrong thing the right way. We also know there are ways to do the right thing the wrong way.

Here it appears the DWR in their scramble to save face, not look bad, and avoid political fallout as priorities over actually addressing root-cause issues and the actual safety of those living downstream, may have been busy doing the wrong thing the wrong way. After all, it’s not DWR’s money and it’s not DWR’s lives and livelihoods at risk here.