AUSTIN — More than 2,100 Texas bridges were classified under the same structurally deficient rating given to the bridge that collapsed in Minnesota and killed at least four people, but state officials insisted Thursday that all the spans are completely safe.
Structurally deficient bridges accounted for 4 percent of the state’s approximately 50,000 bridges in a 2006 report by the Texas Department of Transportation. Seventy-seven percent of Texas bridges were labeled good or better, while most of the rest were deemed functionally obsolete, meaning they were not designed to handle the current traffic demand.
But department spokesman Mark Cross said there is no reason for Texans to worry about a repeat of the bridge collapse that happened Wednesday evening in Minneapolis. The eight-lane Interstate 35W bridge was in the midst of repairs when it buckled during the evening rush hour, sending dozens of cars plummeting more than 60 feet into the Mississippi River and injuring 79 people.
“We talked to our state bridge engineer and that is the first thing he said: Texas has an aggressive bridge inspection program, and all bridges in Texas are safe,” Cross said.
Texas ramped up its bridge repair efforts in 2001, setting a requirement that at least 80 percent of bridges be in good or better condition within a decade. That percentage has steadily increased to 77 percent as of September 2006, the department said in its report.
The new standard was set a month before a towboat captain lost control of four barges in a strong current and slammed into the bridge leading to South Padre Island. The force caused the midsection of the Queen Isabella Causeway to tumble into the water 85 feet below. Motorists drove blindly into the chasm in the road, and eight people died.
The 2001 accident ultimately was blamed on heavy currents, pilot error and insufficient horsepower for the load at hand.
State Sen. Robert Nichols, a Republican from Jacksonville who was a member of the Texas Transportation Commission at the time of the collapse, said the incident made state officials even more cautious about protecting bridges.
Bridges are inspected at least every two years, Cross said, and those with critical issues are checked out more frequently.
Inspectors look for corrosion, deterioration and damage and check for cracks that signal fatigue, said Joseph Yura, a professor emeritus of engineer at the University of Texas at Austin who specializes in structural steel design.
“Like everything that gets older, there’s some deterioration, but that doesn’t mean that the bridge is unsafe,” Yura said. “If it gets to the point of being unsafe, it’s going to be closed. That’s all there is to it.”
Even bridges deemed structurally deficient are still capable of carrying much more weight than could possibly be applied, Nichols said.
Engineers design bridges to hold two or three times more weight than they are expected to carry, Nichols said. That means a bridge is still safe even if deterioration has left it only capable of handling two-and-a-half times the expected amount of weight.
“I think people in Texas can feel very comfortable with their safety on the bridges,” Nichols said.
State Sen. John Carona, a Dallas Republican who chairs the Senate transportation committee, said he hopes the new national focus on bridge safety convinces his colleagues to put more money into road construction and maintenance.
More than half of Texas bridges were built before 1971, according to the transportation department. Of those bridges, more than 9,000 were built before 1950. Many of those aging structures will need to be upgraded or replaced in the near future, said Carona, who wants to raise the motor fuels tax by 10 cents and tie it to inflation.
“While our bridges are safe today, they won’t necessarily be safe tomorrow unless we devise a more adequate funding mechanism,” he said.
On the Net:
Texas Department of Transportation bridge inspection report from 2006: