A federal review of the proposed Trinity Parkway toll road has raised potentially troubling questions about the viability of stretching the 10-mile highway through an extraordinarily sensitive levee system near downtown Dallas.

FILE 2007/Staff photo
The toll road's potential threat to the Trinity River levees' ability to protect from flooding has been a focus of U.S. officials since the Federal Highway Administration released its first environmental review four years ago.

Federal officials released a long-awaited, nearly 4,000-page draft environmental review in the last week, showcasing just how uncertain federal approval remains for a project that city officials say will unlock decades of highway improvements near downtown. Critics worry that it will weaken the Trinity River levees.

The primary threats to the project remain just as they were four years ago, when the Federal Highway Administration first issued an environmental review, only to be met with opposition from the U.S. Army Corps of Engineers, which also must approve the project. The corps insisted the report overlooked possible threats posed to flood protection.

The future of the Margaret Hunt Hill Bridge and other elements of the Trinity Parkway project remains uncertain because of questions raised by federal officials. A draft environmental report makes clear that concerns about flooding and financing for the multibillion-dollar road remain stumbling blocks.

The new environmental report answers those concerns in painstaking detail, but nevertheless makes clear that the two biggest unknowns - how to pay for the multibillion-dollar road, and how to convince the corps that it won't pose a threat to property and people should the Trinity River flood - remain its biggest stumbling blocks.

Still, the report allows the Trinity Parkway's supporters to clear an important regulatory hurdle and provides a clearer view to a possible end to the years-long environmental review process.

"This is absolutely an important milestone crossed, and it's just one more step down the road," said Rebecca Dugger, Trinity River Corridor project manager for the city of Dallas. "There are certainly challenges ahead, but we all have our heads down and are moving forward."

Pushing ahead

But while the city, the North Texas Tollway Authority and the state Transportation Department continue to press forward on the toll road - and on the parks and other amenities that make up the larger Trinity River Corridor project - the report also shows that the corps has lost none of its concern about the impact of the road on its levees.

Some of the same problems plaguing the road surfaced last month in a different context, when the corps issued a failing grade for the Trinity River levees, the 80-year-old dikes between which the city wants to run the toll road.

The city doesn't yet know how bad the problems with the levees are, or what fixes will be required. But one possible solution has been to build concrete diaphragm walls around manmade structures wherever they penetrate the levees.

The corps has proposed the same fix to address some of the concerns it has with the toll road, which will penetrate the levees in five key spots, according to documents included in the report.

The problem, city and NTTA officials said, is that there is no way to know how expensive those walls would be, because the corps hasn't said how wide they would need to be built.

State transportation officials said Tuesday that it is possible the corps would require them to stretch nearly the whole length of the road, a fix that could cost hundreds of millions of dollars or more.

For now, NTTA spokeswoman Sherita Coffelt said, the authority is estimating the walls' cost at about $45 million, though she said that number could change significantly, depending on what the corps requires.

"The challenging part is getting the constructability of the diaphragm walls and getting them approved by the corps," Dugger said. "They are actually pretty new to these guys."

'A huge risk'

For that reason and others, the plan to push ahead on the route between the levees carries significant risks, officials with several agencies involved with the project said Tuesday.

"The NTTA is taking a huge risk in a sense," said Dan Perge, an assistant engineering manager for the state Transportation Department's Dallas district, though he added it was a "calculated" risk. "You cannot preclude the selection of another alternative [route]. If one of those others are picked, everything you have spent in designing it would be lost."

But on Tuesday, federal officials who helped write the draft report repeated warnings that the between-the-levees option remains just one of several possible routes for the road. And officials at all levels said again that the decision about whether and where to build the toll road will be made by federal highway officials, not by state or local leaders. Any route affecting the levees must pass muster with the corps.

"At this stage, we are still looking at all the alternatives," said Anita Wilson, an Austin-based engineering manager for the Federal Highway Administration's Texas division. One of those options, she said, is a "no-build" choice.

Dugger conceded that pushing ahead was a risk - and that the city has no guarantees that the highway administration won't require another route altogether.

"That's why it is called at-risk," she said. "We've always been upfront, very upfront that this is at risk, and that something could happen at the end. But it was a risk we felt we needed to take."

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