The California Department of Water Resources acknowledged this week that many cracks have appeared in the new concrete of the Oroville Dam spillway, which cost over $500 million to repair.
The State of California is believed to have spent $100 million each month on Oroville Dam during February, March and April in a crisis effort to try to stabilize America’s tallest dam, which suffered a near collapse and forced the evacuation of 200,000 downstream residents earlier this year.

The Kiewit Corporation, which was issued a $275 million contract in April to repair both of Oroville Dam’s main and emergency spillways, poured a 1,700-foot cement top sheet and then roller-compacted and smoothed the spillway’s surfaces shortly before the November 1 contract deadline. The California Department of Water Resources (DWR) inspected the work and certified the first phase of the massive repair job was completed on time.

But the Sacramento Bee reported 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” on the repaired spillway and to recommend any further steps necessary to address infrastructure risks.

The California Division of Dams wrote a letter to FERC on November 7 to reassure regulators that “the presence of hairline cracks was anticipated and is not expected to affect the integrity of the slabs.” DWR spokeswoman Erin Mellon added, “All concrete has this result in the placement. It’s just physics of how concrete works.”

But KQED reported that Robert Bea, a professor emeritus of civil engineering and founder of the highly 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 could increase stresses on concrete.

The CCRM has issued several reports documenting that the state was aware of serious cracking in the Oroville Spillway as far back as a 1998 inspection report. DWR did try to patch some cracks and fill up visible voids. But CCRM dam experts stated that finding hollow areas is like trying to find a stud behind a wall by tapping it with a hammer.

Bea’s group is especially alarmed by green grass that has continued to grow on the dam’s abutments during the hot summer and fall. The lush green grass indicates there has been seepage through the dam face for about 50 years. CCRM does not accept DWR’s explanation that the seepage is not a risk, because it is just some “natural springs.” CCRM warns that any seepage through an earth-fill dam should be extremely worrisome.

http://www.breitbart.com/calif...-500-million-repair/

Sounds like the saga will continue. The next significant water event will test it all over again.

It is worth mentioning that Bob Bea has made a career out of sensationalizing trivial shit, and those of us that know him do not put great stock in his opinions. That does not mean, of course, that he is wrong in this particular instance. OTOH, California government agencies don't have a particularly stellar record, either.

Question for the civil/structural engineers...

What are the odds of sudden catastrophic failure of this thing? Is it a possibility, or would it be more “gradual”, like almost happened last time - as in at least enough time to evacuate everyone in the flood zone?

-Rob

Hope they got the extended warranty!

quote:

Originally posted by BurtonRW:
Question for the civil/structural engineers...

What are the odds of sudden catastrophic failure of this thing? Is it a possibility, or would it be more “gradual”, like almost happened last time - as in at least enough time to evacuate everyone in the flood zone?

-Rob

Hard to say, in general, without knowing specifics of the design. But, particularly for large, life-safety structures, they should be designed with significant redundancy so that collapse, if it happens, should be more "gradual." There are exceptions, of course, and part of it depends on one's definition of "sudden." If by sudden, one means in a blink of an eye all is hunky-dorey, and then, in a fraction of a second, the whole thing falls down, then those are very rare. Even the World Trade Center Towers took awhile before they fully collapsed. Engineers refer to this as "ductile" failure, so that significant, noticeable defects are readily apparent before collapse. Depending on the loading, and specific mode of failure, even ductile failures may progress fairly rapidly. Hence, once the warning signs are noticed, one should not delay in evacuating. For highly values/important structures, not only is significant redundancy designed in, but specific failure modes are designed into the structure so that, when it does fail, it does so in a manner that prevents, or minimizes, loss of life.

I like the idea of making a new spillway from scratch. Empty the structure, over-engineer the crap out of it. But no one has an extra three billion. California is spending their money on Fluffernutter pensions ...

There are bound to be cracks in that large a bandaid solution.

And make no mistake, that was a bandaid solution.

A permanent solution would be very, very expensive and take years, not months, to do.

Hope that dam is just upstream of Sacramento

From what I have gathered...

They've spent 650 million and completed stage one. Stage two has just started and will take until 2019.

FEMA to fund 75% and the water users the rest.

quote:

Originally posted by cparktd:
From what I have gathered...

They've spent 650 million and completed stage one. Stage two has just started and will take until 2019.

FEMA to fund 75% and the water users the rest.

Damn that's a lot of dam money.

Some dam guy was going to start the dam jokes, and you damn well know it.

quote:

Originally posted by BurtonRW:
Question for the civil/structural engineers...

What are the odds of sudden catastrophic failure of this thing? Is it a possibility, or would it be more “gradual”, like almost happened last time - as in at least enough time to evacuate everyone in the flood zone?

-Rob

I can't really speak for the Orville Dam but I can tell you that catastrophic failure of earthen Dams is possible under the right conditions. In my youth, I ran an agricultural construction project that included an earthen reservoir that held back 800 million gallons of water. I was actually the designer of the reservoir and the flood control pumps that filled it. It was for a 1000 acre citrus grove we built in Florida. Unfortunately 2 things happened that caused 300 feet of the dike to fail spontaneously. The first was back to back rainstorms that exceeded the reservoir capacity with a grove manager that decided to throw plywoood sheeting over the spillways and put 4 extra feet of water into the reservoir. (The freeboard was 6 ft to allow for wave run-up). The second, and most critical thing, was an 8-9 foot gator that apparently dug a cave/nest into the reservoir berm. The extra pressure from the water and the weakening from the cave allowed the first 50ft to blow-out and when it was all said and done 300 ft of berm had to be rebuilt.

The wall of water didn't hurt anyone since it was in the middle of a 1000 acres. It did however uproot about 5 acres of 5 year old grapefruit trees. They told me they were picking up 5 and 6 lb Bass all over the place. I was just glad the secondary reservoir didn't let go from the sudden change in pressure and realease the other half of the water storage.

This happened a number of years after I was off the project. But I knew I should have shot that dam gator when I was surveying through the sawgrass for the reservoir and ditches. I heard that bastard barking a numer of times. (Always carried an old Mossberg pump shotgun when surveying in Florida)

So, to answer your question, yes, earthen dams can undergo catastrophic failure under the right conditions. Sounds like they have some "piping" occurring and that could be really bad news. Usually that can be managed by lowering the level and dumping a lot of impermiable fill material over the area where the piping comes from. I.E. the wet side of the dike.

Ken

https://www.youtube.com/watch?v=8F9irn-u6no

Here is Juan Browne's latest update. He will have another update in several days. He got an award for his reporting on Oroville Dam. One of my favorite posters.

Defective Mexican concrete.

Couple of big cans of this, and they should be all set.

quote:

So, to answer your question, yes, earthen dams can undergo catastrophic failure under the right conditions. Sounds like they have some "piping" occurring and that could be really bad news. Usually that can be managed by lowering the level and dumping a lot of impermiable fill material over the area where the piping comes from. I.E. the wet side of the dike.

Was it not up in North Idaho a couple decades ago where 2 earthen dams let go? The upstream on blew out and the wall of water took out the lower one as well. Did some major damage to a town or two as I recall.

quote:

Originally posted by 41:


https://www.youtube.com/watch?v=1zFkgb1cmgg

That there is what I call some dam good aggregate information and concrete facts.

It's like deja vu all over again.
Search for "St. Francis dam" on YouTube.