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The Story Behind The Katrina Story

Forget the Superdome and a few thousand people who were uncomfortable for a few days. The real story of Katrina has yet to be told. How did a "State of the Art" floodwall become a 200 billion dollar engineering failure?

http://wizbangblog.com/images/katrina/breakclose-thumb.jpg

Study hopes to dig up dirt on floodwall failure

As engineers analyze why some New Orleans canal floodwalls broke during Hurricane Katrina, a central focus will be Louisiana's notoriously soft, wet Mississippi Delta soil.

The floodwalls are hard structures embedded in soft material. As Katrina's storm surge filled up the 17th Street and London Avenue canals, it put high pressure on the walls and soil. If the surrounding soil is already unstable or the structure is not properly lodged in it - it can move and bring the wall down.

Simply put, that's not good enough. You don't have a 200 billion dollar failure and say "We'll it was really tough." It is not tough. The earthen levees -most of them 30 years old- held and the new "start of the art" floodwalls failed. Saying, "Well, you know, the ground is squishy around here" doesn't cut it. Engineers solve problems like this. - Well good engineers do.

The Corps and outside engineers say it's too early to tell what went wrong, and that walls probably failed for different reasons in different places. In eastern areas of the city, where the Industrial Canal is located, floodwalls were clearly overwhelmed by high water beyond their design specs. Engineers are focusing much of their attention on the 17th Street and London Avenue drainage canals, where storm surge was lower and may not have overflowed the walls - pointing to a possible flaw in design, construction or maintenance.

I've been hesitant to post any firsthand knowledge or evidence because frankly it is beyond my scope of expertise and I spent less than a day studying it... But I examined the breach in the floodwall at the 17th street canal and frankly I would be hard pressed to argue that the water came within 4 feet of the top of the wall. Statements from engineers who have done more complete examinations support my limited observations.

Given the above let me say this. If the floodwalls gave way when the water was still only about halfway up the side of the wall, it may go down in history as the worst engineering flaw in the history of mankind. Many people -especially the ones who live 1000 miles away and aren't engineers- have said the the levees were bound to fail because they were not rated for a direct hit from a category 5 storm.

The problem with that, of course, is that Katrina was a category 3 storm and it hit Mississippi. New Orleans got a glancing blow from the weak side of a category 3 storm. Certainly any structure that was designed to withstand a direct hit from a cat 3 storm should have held.

The levee break on the Industrial Canal is somewhat more understandable. They say the water was far higher than the levee. Taking that at face value, the coastal erosion in the area south of the levee has been dramatic for the last few decades. The levee is considerably closer to the Gulf of Mexico than when it was designed. If the storm surge was higher than it was designed for, that is not necessarily indication of a design flaw but perhaps and indication of the changing parameters of the area.

The other two areas, (17th street and London Ave) which are getting considerably more scrutiny, are on Lake Pontchartrain. These have floodwalls which are made of sheet pilings driven into the ground and concrete poured over them..

http://wizbangblog.com/images/2005/10/floodwall-thumb.jpg
I didn't take this picture to show the width of the wall
but as you can see from the guy leaning over it,
the wall is probably about 24 inches thick.
(Click for a larger view.)

...Designers can lessen the upward pressure by putting the structure deeper into the earth; that way the water has farther to travel and the pressure is lessened. But some observations by LSU scientists indicate the sheet piling might have been unusually short - just a few feet long.

Driving sheet piling "has several functions," Bea said. "The first is to prevent water intrusion below the base of the wall below the ground level. The other important function is to support the wall both laterally and vertically. We have all kinds of photographic evidence that says those walls did not get the support they needed, and over they went."

A few quotes from a single academic is not exactly incontrovertible evidence but the above statements are nonetheless quite troubling. Although, I'm not sure they can be altogether accurate. I'll try to get some pictures to make it more clear, but I've watched them put in sheet pilings. The pilings have holes on the top end to loop a chain thru to raise it up. If they only put it a few feet in the ground, the construction crew would then have to cut the top off with a torch. That would be a slow process that would make it abundantly clear the piling was not in deep enough. The LSU guys claim to have photographic evidence but I'm still taking this one with a grain of salt.

The whole story will unfold in the years and decades to come in the court system... but in the mean time, I can't wait for the Discovery Channel version. Early indications are that this was more than just an act of God... It looks like the flawed hand of man had more than a little to do with it.

Update: A few folks in the comments have (rightfully) made the point to separate the engineering from the construction. That is a big point I should have made. I called it an "engineering" failure because in the generic sense it was a failure of an engineering project... But if we are looking for the true flaw, construction is, of course, half of the equation.


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Comments (9)

Try to examine the junction... (Below threshold)

Try to examine the junction between the concrete and the sheet pile of damaged sections. On Thursday or Friday I plan to publish criticism of yesterday's post Apple Eats Cajuns for Breakfast.

Good engineering design can... (Below threshold)

Good engineering design can be undermined by shoddy construction. That sure looks like what happened, from what I've seen.

J.

The levee failed becuase th... (Below threshold)
spurwing plover:

The levee failed becuase the eco-freaks at EARTH JUSTICE and the SIERRA CLUB opposed fixing a levee becuase it would harm the invisible levee guppy

I would not be surprised at... (Below threshold)
Mike Boelter:

I would not be surprised at the discovery that the pilings were only driven a few feet into the ground and then cut off. Think of the amount of money one could save if you drove 30 foot steel pilings 5 feet into the ground and cutting them off with 5 feet above (instead of 25 feet down with 5 feet up top. Why each section of piling will fill in three 'slots' instead of one slot per piling.

Heck once you get the knack of it you can even settle for 2 feet in the ground and 5 feet out and have that single piling fill up 4 slots.

Of course you bill the government for the full number of pilings, take the savings and run to the bank, not to mention sharing some of the booty with members of the Orleans Parish Levee Board and the inspectors from various agencies.

Not saying that this is the way it was done, but as a former resident of New Orleans, (moved out in 1989) it would not surprise me.

JLawson, your comment is wh... (Below threshold)
Wanderlust:

JLawson, your comment is why good procurement personnel ensure that design/build projects are centrally managed, instead of pieced out separately (that is, engineering to one company, and construction to another).

Besides that, it's the customer's responsibility to ensure that construction oversight is up to par - so that flaws in either engineering or construction can be discovered and corrected as quickly as possible. Otherwise, by the time the damage is discovered, fixing it means you've got a huge f*ckup on your hands.

Just ask Bechtel what happens when construction oversight is shoddy on a large project (regarding the Big Dig).

No matter who is ultimately at fault - shoddy engineering or shoddy construction - the ACE was responsible for handover at the end of the job. It was their responsibility to ensure that someone knowledgeable watched over each phase of the work, and accepted the job as being complete only if it really was complete.

If, as has been alleged, the ACE accepted the job when Pittman raised concerns, the ACE is going to have to answer for their decision to accept it.

(I know, a lot of this info sounds redundant, but so are construction engineers, and for good reason.)

Jay is correct. I remember ... (Below threshold)

Jay is correct. I remember a case study in the middle of "Engineering Ethics", a course I took while a senior engineering student.

The Hyatt Regency Hotel catwalk failure

What the contractors actually built was not what the engineers designed. To point out an example, what was designed was that the supporting poles for the catwalks were supposed to be unbroken, however the constructed supporting poles were broken between each catwalk, and the resulting couples (by the offset) caused unaccounted for stress (amplified by the rythmic stomping of the patrons) that most likely resulted in the collapse.

To point out an example,... (Below threshold)
Steve L.:

To point out an example, what was designed was that the supporting poles for the catwalks were supposed to be unbroken, however the constructed supporting poles were broken between each catwalk, and the resulting couples (by the offset) caused unaccounted for stress (amplified by the rythmic stomping of the patrons) that most likely resulted in the collapse.

The load of the catwalks was supposed to be carried by the roof structure of the building. Because of the change made during the construction, the load of each catwalk was instead carried by the catwalk above it which, of course, had not been designed to carry any load at all. As a result, the upper catwalk failed and dropped the lower catwalk.

The sheet pile acts as a ca... (Below threshold)
Kelleher, William J.:

The sheet pile acts as a cantilever and the bending moment is a function of the height of water cubed. Unless the sheet pile had a large section modulus, which I doubt, the levee would fail. If the sheet pile was not driven deep enough to obtain a resisting moment, failure occurs. If the sheet pile, over its entire depth,encounters an old buried swamp, failure can occur. Differential settlement can cause small cracks between individual rigid panels causing water to pipe out the dry side eroding the soil that supports the sheet piling. Water could also overflow the dam and erode the supporting soil. Shoddy construction and/or poor inspection only makes matters worse. All reasons can cause a catostrophic failure over the entire depth of floodwall plus the earthen levee. The Corps knew with an absolute certainty that the floodwall or dam was bound to fail if the height of water was greater than 11 feet above sea level. Inadequate funding by congress is no excuse, engineers have a moral and legal responsibility to inform their clients of the lost of lives, property and the horror to residents that will occur when a dam bursts. The canals should have been damned off at Lake Pontchartrain years ago.

If the residents of New Orl... (Below threshold)
Kelleher, William J.:

If the residents of New Orleans were workers in an excavation OSHA would bring up the Corps and the contractors on criminal charges. See California's OSHA regulations for excavations.




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