This is going to require more than a thumb in the dike

The Dallas Morning News, on its transportation blog, contains an item today about yesterday's release of the Army Corps of Engineers' inspection report of the Trinity River's levees and its headline asks "Does this mean the Trinity toll road can't be built?"

What kind of question is that? Anyone reading the Corps' report should be asking only one question: "What must be done to protect downtown Dallas from a Hurricane Katrina-like catastrophe?" Any other questions pale in importance to this one.

City officials have repeatedly told us the levees are designed to protect us against a flood that only has one-eighth of 1 percent chance of hitting the city. That's an epic flood, an Old Testament belly washer. However, what this latest report shows is that our levees can't even protect us from a 100-year flood, the kind that hits ... well, the last one of this magnitude hit Dallas 101 years ago. Uh-oh!

Wait a minute! It gets worse. A team of experts reviewed the corps' findings, found them accurate and then added they weren't sure the levees could withstand the flooding that occurred here in 1990.

Now the city claims we shouldn't have to worry about that because the levees today are 14 feet higher than they were in 1990. Wrong argument. The concern is not that the water will crest over the top of the levees; the concern, according to the corps' report, is that the cracked earth found throughout the levees mean they won't hold and the water will come crashing through them.

Here is the section of the report (found on Page 55) that really bothered me:

"The semi-arid, windy environment found in the North Central Texas area renders the highly plastic clays that comprise the levees prone to desiccation. As a result, desiccation cracks are the usual conditions for the Dallas Floodway Levees. These cracks frequently extend deep into the levee cross-section, both parallel and traverse to the levee crest, and are believed to be a significant contributing factor in the development of shallow slides of the levees; more than 300 of which have occurred since the USACE completed reconstruction of the levees in 1958. It should be noted that although referred to as 'shallow' slides, these slides are generally deeper than what is considered 'normal' for most shallow slides. This is due to the deep desiccation cracks that develop in the moisture deficient embankments. Slides as deep as 15' are reported to have occurred after cracks have become filled with water. ... Examination of the moisture contents of levee samples obtained by USACE in 2004 indicates more than half of the samples had moisture levels less than the plastic limit. These samples were found at depths just below the levee crest to more than 30' -- essentially the full height of the levees, so deeper cracking is theoretically possible. The standardized Inspection Checklist used for Periodic Inspection indicates that any cracking deeper than 6' feet deep is considered to be 'Unacceptable'. Under this criterion, it will be a long-term challenge (emphasis mine) for the 23 miles of Dallas Floodway levees."

Here comes the hard part. How does the City fix this? The Corps lists three methods, two of them stop-gaps, one a permanent fix. If the City is serious about the long-term protection of its citizens and its core downtown area, it needs to go with that permanent solution:

"To accommodate desiccation cracking, the existing levees could be replaced with structural walls (T or L-base walls). Alternatively, structural walls or barriers (diaphragms) could be incorporated into the levee cross-section. Each of these options is very expensive (again, emphasis is mine), but they are alternatives that could be properly designed and constructed to enhance the integrity and performance of the protective works as mitigations for the desiccation cracking."

Less than a month ago, I sat in a banquet room at the Lakewood Country Club to hear Dallas City Manager Mary Suhm deliver her latest "state of the city" address and she said ... and this is an exact quote ... "The Trinity River Corridor Project is first and foremost a flood-control project." If that's so then here's what the City of Dallas must do and must do immediately:

Forget about the Calatrava bridges, the chain of lakes, the toll road, the promenades, the overlooks, the soccer fields, the jogging paths and everything else that was supposed to be part of this project and put all available resources into fixing those damn levees and fixing them now!

Because here's what happens if those levees are not fixed: If the Corps finds that the levees are unacceptable, that would mean Dallas would not be eligible for any federal disaster relief assistance if and when The Big One comes.

What scares me is that the City may instead decide to fight the Corps findings, instead of fixing the problem. According to this Morning News report, "specialists hired by the City will spend weeks, and probably months, investigating whether the flaws found by the inspection are as bad as the corps' worst-case fears would indicate. The City will also hire a firm to begin assessing the levees in an attempt to convince the U.S. government that they can withstand a 100-year flood."

Oh, that makes me feel a lot more secure.