Searching for problems under the Trinity River levees

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by BRAD WATSON / WFAA-TV

wfaa.com

Posted on December 10, 2009 at 12:02 PM

DALLAS — There's lot of concern from the federal government and the City of Dallas about bridge piers built into the Trinity River levees that could weaken them.

The levees protect tens of thousands of people (and $7 billion in property) from flooding. But a recent levee slide points to another hazard: Pipes buried in the levees.

The search is on to find them all.

Levee sections usually give way after heavy rains, when too much water seeps into cracks, turning the soil to mush. Gravity does the rest.

But a recent slide near Interstate 35E and Regal Row was different. A leaking city water line soaked the soil, showing why pipes buried under and crossing through the levees are hazards, too.

"There are seepage issues related to penetrations; kind of the same thing we have with bridge piers that might be in the levee," said Kelly High, a spokesman for the city's Trinity Watershed Management Department.

There are nearly 23 miles of levees along the Trinity River as it winds through Dallas, and it's not just water mains buried in them.

A critical Army Corps of Engineers inspection also found pipes carrying jet fuel, natural gas, and oil, along with abandoned sewer lines.

The city believes there are dozens of these potential problems, leading to new questions.

"Are these crossings causing any problems? Are they properly armored?" High asked.

The city believes it can locate all the pipes and lines buried in the levees. Even so, the Corps inspection report found that in some locations there are many yet to be identified.

At the Central Wastewater Treatment plant along the river at Interstate 45, huge pipes run through or under the levee. But an inspection indicated there are many other utilities yet to be found.

"We'll go through individually and look at each one of those crossings — how they were built, look at the plans, and make sure that they are done appropriately," High said.

What's clear is that the Corps won't easily allow intrusions through the levees any longer. The Corps has already nixed the city's plan to bore under the levees to insert conduit for wiring to light the new Margaret Hunt Hill bridge now under construction.

"Because that provides an opportunity for potentially water to kind of infiltrate and kind of run along the line and weaken the levee in that spot," said Assistant City Manager Jill Jordan.

So the wiring will go up and over and attach to the bridge.

This recent soft soil is a hard lesson on buried pipes, and the risk of what else is below that could lead to break during a major flood.

E-mail bwatson@wfaa.com

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