Corps Warns that Trinity River Levees Pose a Flood Risk to Downtown, but is City Hall Listening?

This scene—a man wading to save his baby from the Katrina floods in New Orleans in 2005— will be our scene in Dallas if the Trinity River levees break.

Now that the truth is finally coming out about the Trinity River toll road project, it makes a difference to remember who said what two years ago. And not just as gotcha.

The Trinity River toll road is in trouble now because the basic due diligence on it never took place— not two years ago when we were voting on it in a referendum, not in the entire decade since we first authorized the Trinity River Project in an election in 1998.

These are some bad old chickens coming home.

Last week, after the U.S. Army Corps of Engineers announced that Dallas' Trinity River flood control levees are "unacceptable," meaning they are unsafe, I went back and listened to some tapes I had made to write about the issue.

One reason the Corps said the levees aren't safe is that Dallas has allowed trees to grow in and near them. Levees, the earthen berms along the sides of the river that protect downtown from catastrophic floods every spring and fall, are made of clay. Tree roots in or near levees create cuts in the clay that may allow scouring floodwaters to tear the levees apart.

In the run-up to the 2007 referendum on the Trinity River toll road, opponents of the toll road cried foul when toll road backers promised the road would be screened from view by a small forest of trees that the city would plant in the levees. City council member Angela Hunt and former member Sandy Grayson pointed out that planting trees in levees would be a violation of Corps of Engineers safety standards.

One recording I listened to was of a pre-election debate at an Oak Cliff school. Clear as a bell on my recording, Dallas Mayor Tom Leppert assured the audience that the Corps of Engineers had "signed off" on the tree issue. In fact, he promised that the Corps had signed off on all aspects of the toll road design.

"The Corps has signed off on the tree issue," Leppert told the audience. "They have signed off on the safety issue. They have signed off on the environmental issue. They are the experts. Don't take our word for it."

We know now that the U.S. Army Corps of Engineers hadn't signed off on anything. Still hasn't.

Leppert repeatedly promised Dallas voters he had an agreement with the North Texas Tollway Authority by which the authority would provide all funding for the toll road beyond the relatively nominal sum Dallas voters agreed to contribute in the original bond election in 1998. Remember? He said over and over again that he was "very comfortable" with assurances he had received from the NTTA.

We now know that the NTTA is a billion dollars short of the cost of building the road and can't come up with the money.

During the run-up to the 2007 referendum, Leppert often cited his experience as former CEO of Turner Construction, one of the world's biggest construction companies. But in fact he rose to that position from a career as a management consultant rather than as a construction engineer.

Maybe if the mayor's office had been occupied by a person who actually knew construction, someone in that office might have asked better questions about soil conditions in the Trinity River floodway where Dallas proposes to erect a major new highway, much of it on concrete piers.

If someone had insisted back then on knowing what kind of soil lies beneath the proposed road bed, they might have come up with the answer that has them all jumping out of their skins now.


That's the concern. Sand may lie beneath the floodway. If extensive amounts of sand are down there, as tests are about to determine, then sinking a series of massive concrete piers into the floodway would be very risky, indeed.

At the end of last week, I had a detailed and helpful conversation with Kevin Craig, who is manager of the Trinity River project for the Corps of Engineers. I wanted to know more about what was wrong and why it took the Corps so long to reveal results of tests it did back in December 2007.

The answer was that the original test results sort of went out the window last year when a contractor began drilling 54-inch diameter shafts 90 feet into the soil for the Margaret Hunt-Hill "signature" bridge. The drillers hit sand.

Craig told me the Corps decided it needed to go back and review its data after the sand came up out of the bridge pier shafts. He said sand tends to occur in layers, not pockets. He said piers sunk into sand create a difficult problem and danger.

I asked him if the danger is that flood water might follow a pier down beneath the surface of the floodway and find its way to the sand. The danger then would be the water excavating the sand, hollowing out collapsible caves beneath the levees and roadway.


He said, "Yeah. Any time you have a connection of natural ground with some manmade structure, concrete or whatever, it's really hard for there to be a sealed connection there."

To dampen concerns over these issues, the city manager's office already is talking about using "diaphragm walls" to protect the piers. In New Orleans, diaphragm walls have been used to bolster bad situations that already exist—levees built with bad soil or on top of bad soil in places that have to be protected.

But diaphragm walls are an expensive work-around, a kind of band-aid. If someone could invent a diaphragm that formed a 100 percent reliable seal in a wet dynamic environment, we wouldn't need birth control pills.

This whole thing is up in the air now. The stakes are absolutely staggering. If the Trinity River levees ever breached with the river at full flood stage, downtown Dallas would be inundated.

Last week's announcement was a bombshell. It means the levees are already unsafe, and that's before being subjected to the additional pressures a highway between them would create. A real bombshell.

The whole Trinity River project has always been risky. It would never even have been launched in the first place if Dallas had not succeeded in winning a key waiver from flood safety standards.

The core concept here is a bit technical. Called "valley storage," it's a measurement of how much rainfall can seep into the ground without rushing into the river and causing it to rise. Dallas was under a court order not to build anything that would worsen that situation. The city had to get a special waiver to build this project, because the project itself does worsen valley storage.

A flood control project that makes flood dangers worse. Go figure.

Even though the waivers are on record and a fact of history, Leppert has repeatedly and emphatically denied that any waivers exist. Leppert was challenged in the debate in Oak Cliff by a questioner who wanted to know why the city would seek waivers that might compromise the safety of people and property. Leppert said, "Very straightforward again, there are no waivers and no exceptions."

In the same Oak Cliff debate, Leppert told the audience, "I can assure you that the city is doing nothing that would weaken the levees. And don't take my word for it. Take it from the Army Corps of Engineers, because they are the ones that have the responsibility."

If this whole situation weren't so grave—if lives and property were not at stake—we could almost have a chuckle over the things that have been said by the toll road boosters. For instance, the same night Leppert vowed that the Corps was OK with trees in the levees, former city council member Veletta Lill gave her own version of the tree issue. Listening to it again, I was reminded of the character Fred Armisen plays on Saturday Night Live—Nicholas Fehn, political comedian.

"It is our understanding that you can put the trees in the floodway," Lill said. "The Corps has said you can put in all the trees you want in the floodway. So if you put those trees along the roadway to shield the road, I don't think you are as concerned about the actual drivers as you are about those folks in the park. So you can put any kind of trees you want down in the floodway that you want. So if you put those trees on the other side and they shield the road, tell me again why it's a risk?"

On October 21, 2007, Dallas Morning News columnist Steve Blow published the results of his own engineering study of the Trinity River project: "I have been down there between the levees on a bike. It feels huge. That big, green swath certainly seems wide enough to accommodate both a roadway and a lot of recreation. Or is that just wishful thinking on my part?"

I guess we could smile at some of it—Leppert's blithely false assertions, Lill's loopy tree math, Blow's big bike ride. Maybe one day I'll smile.

But not now. Surely we learned from Katrina. Surely we can find the connection. We look out there every spring and fall and see a vast body of water at the foot of downtown held at bay only by earthen levees. We have to understand that we might have elderly people drowning in their wheelchairs in nursing homes exactly the way New Orleans did.

Don't the mayor and the city council have at least a moral obligation, if not a legal one, to carry out the due diligence that has never been done before? By that, I mean asking hard questions about flood dangers that already exist because the levees are weak and asking about the additional risk that may be posed by the highway project.


The Dallas Morning News editorial page had its own very odd take on this issue last week, complaining that this whole business of a warning from the Corps about unsafe levees was very inconvenient:

"No one would suggest endangering lives or property for expediency, but this is getting ridiculous," the paper said in its official cranky voice. "What of the toll road plan Dallas voters have twice approved? What of the taxpayer dollars already sunk into the project?"

I read that one part several times, and each time I wondered what was getting ridiculous? It's ridiculous for the Corps to warn us that the levees might collapse?

Listen, I want to be warned. I seriously want to be warned. Corps of Engineers, are you listening? Warn me. If they don't want to be warned at the News, fine. I do. I will not be cranky. I will be running.

Sponsor Content


All-access pass to top stories, events and offers around town.

Sign Up >

No Thanks!

Remind Me Later >