Corps: Levees may not protect downtown

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by The Dallas Morning News

wfaa.com

Posted on April 2, 2009 at 8:02 AM

Updated Monday, Oct 19 at 4:58 PM

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Brad Watson reports

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The U.S. Army Corps of Engineers is no longer certain the Trinity River levees can protect downtown Dallas from a flood like the one that took place in 1990. Flaws up and down the 80-year-old earthen dikes have raised questions about their integrity, and could require massive fixes.

The corps issued those bleak assessments Wednesday as part of a final report on its 2007 inspection of the levees. The problems identified range from deep layers of sand that could complicate construction of the Margaret Hunt Hill Bridge to "severe" cracking throughout the levees that could be difficult and costly to repair.

"This current information questions the ability of the system to pass the current 100-year flood or a repeat of a May 1990" flood, said Dr. Monte L. Pearson, a corps levee expert and leader of a team that reviewed the findings by the corps' Fort Worth office. "The [inspection] documents numerous deficiencies, which appear to be degrading over the last several decades."

The corps said Wednesday that 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. The corps announced Wednesday that it has withdrawn its assessment that they can do so. If they can't, insurance rates will spike for property owners within the flood plain.

It's possible those investigations will ease some of the corps' concerns, said Kevin Craig, the corps' Trinity River project director. If that's the case, impacts on the biggest projects in the levees - including the Calatrava bridges and the Trinity toll road - could well be manageable, he said.

"Certainly, things could be delayed," Craig said. "It is difficult to say for how long. The first thing we have to do is the investigations, and before we make those types of conclusions, we have to do the analysis to determine what the real characteristics are. Then we and the city will have to agree on a long-term plan" for fixing the levees.

Without knowing the extent of the repairs that might be needed, it is unknown how much they might cost. The city would be responsible for finding the money for the work, though it could seek federal assistance.

Dallas Mayor Tom Leppert said the levees' problems need to be resolved. But he said they don't necessarily mean the bridges and the toll road can't be built.

"It is important to keep in mind what this is all about. This is not re-debating everything having to do with the balanced-vision plan, the Trinity corridor river project. What this is about is addressing the levees. If we didn't do another thing, we would still have to fix these levees," he said.

The city staff also worked overtime Wednesday to reassure City Council members that troubles with the levees will be addressed.

Assistant City Manager Ramon Miguez, who is charged with levee upkeep, defended the levees as safer than the report stated.

He told council members that his most important message to them was that though the city does recognize deficiencies in the levees, "the corps has not provided an engineering analysis to demonstrate that the deficiencies prevent the levees from performing during the 100-year flood."

He also said that during the May 1990 flood, the levees "performed as expected."

The Federal Emergency Management Agency will immediately begin redrawing flood-protection maps for businesses and other property within the downtown Dallas flood plain. That process will take 18 to 24 months, during which time the city can try to correct the problems and seek to have the levees recertified.

To do so, the engineering firm it will hire within one to two months will have to make the certification that the corps said Wednesday that it can no longer provide.

If it can't, the new maps will be drawn as if there is no levee at all, and property owners within the flood plain could see insurance rates rise sharply, and development could be stopped.

Another result of the failed inspection is that the corps will no longer rate the levees as "acceptable."

That means they will no longer be eligible for federal rebuilding funds should they be damaged or destroyed in a disaster. That could leave the city in need of tens, or even hundreds, of millions of dollars or more, just when it is dealing with a major disaster.

However, the city and the corps said Dallas will immediately apply for a waiver to keep it eligible for the funds while it works with the corps to come up with a plan - and the money - to fix the levees.

News that Dallas will soon lose FEMA accreditation and risks having its flood plain map radically expanded came as a shock to many on the City Council, even though elements of the report have been circulating since February.

Council member Mitchell Rasansky urged the city's management to make levee repairs Dallas' highest priority.

Council member Angela Hunt, who led a campaign in 2007 to stop the Trinity toll road project, sharply questioned why the city would continue to move forward with engineering for a planned toll road between the levees in the wake of the corps' findings.

"Some of the leadership in Dallas has placed considerable pressure on pushing through the approval process" for the toll road at the risk of levee safety, she said.

Leppert took issue with that, saying no one at any level has put the road ahead of safety.

Assistant City Manager Jill Jordan, who oversees the city's Trinity River project, said the toll road plan actually is helping because it has given the city a head start on performing geotechnical analysis of the levees that will be required to satisfy the corps' demands.

But problems highlighted in the report about the impact of existing bridges on levee integrity underscore why the corps is so concerned about the Trinity Parkway toll road and the Margaret Hunt Hill Bridge.

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rbush@dallasnews.com

MORE PROBLEMS IDENTIFIED IN REPORT

Utility line encroachments

Problem: Hundreds of levee penetrations by utility lines exist throughout the floodway.

Action needed: Each encroachment needs to be evaluated for impact on the protective works. Negative impacts should be mitigated without delay.

Bridges

Problem: The levees are degraded by the penetrations of at least 23 bridges, allowing seepage.

Action needed: Encroachment impacts will be addressed as part of approved rehabilitation efforts.

Crest heights

Problem: At least 47 percent of the east levee crest and 42 percent of the west levee crest are not high enough.

Action needed: Restoration of crests to necessary heights will be addressed as part of approved rehabilitation efforts.

Cracks in levees

Problem: The levees are extensively cracked because of drying soil.

Action needed: There are no easy corrections for cracking. Possible options include removal and replacement, overbuilt sections and structural measures.

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