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FRIDAY, AUGUST 3, 2007
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The Tennessee River bridges near Decatur carry cars north and south on Interstate 65. More than 35,000 vehicles cross the bridges each day.
Daily photo by Jonathan Palmer
The Tennessee River bridges near Decatur carry cars north and south on Interstate 65. More than 35,000 vehicles cross the bridges each day.

No danger of collapse?
I-65 bridges operating
as intended, engineers say

By M.J. Ellington
mjellington@decaturdaily.com · (334) 262-1104

MONTGOMERY — Despite similarities to a bridge that collapsed Wednesday in Minnesota, state engineers say the interstate bridges at Decatur are operating as intended.

There is no indication, they said, that either of the 31/2-mile Interstate 65 spans across the Tennessee River has the problems that engineers found in the Interstate 35W bridge in Minneapolis.

Inspectors raised concerns about the Minneapolis bridge as long ago as 1990.

Collapses hard to predict

But until it's known what caused the Minneapolis bridge collapse, Alabama experts say it's hard to predict if a similar failure could occur here. Still, transportation officials here say drivers should not be alarmed.

Jim Richardson, a civil engineering professor at The University of Alabama, said Thursday that he believes the cause will come down to one or more of three possibilities: steel corrosion caused by the salt used to de-ice roadways, steel deterioration or bridge design.

Only the design factor is a question here, given Alabama's warmer climate, he said.

Richardson said the bridge that fell was a design often used on interstate spans in the 1950s and '60s, with supports at each end of a span but not in the middle. After 1967, engineers no longer used that design, he said.

"Bridge collapses happen but are rare," said Alabama Department of Transportation spokesman Tony Harris.

Compiling bridge ratings

The state has 100 bridge inspectors who check the state's bridges at least once every two years, he said. High-traffic bridges often receive more frequent examination. Harris said DOT is compiling a list of Alabama bridges and their ratings but that list was not yet available.

George H. Connor, DOT assistant state maintenance engineer for bridges, said the Interstate 65 bridges, whichabout 35,800 vehicles cross each day, had routine inspections within the past year. They opened to traffic in October 1973.

Connor said inspectors also conduct underwater checks on bridges in water that is at least waist deep, as it is along I-65 across the Tennessee River.

DOT posts weight-limit signs on all bridges in the state with structural problems. Connor said neither the I-65 bridges nor the two even busier bridges that cross the river at U.S. 31 in Decatur have weight-limit postings.

Hudson Memorial Bridge

DOT Division 1 Engineer Johnny Harris said the state built a new northbound bridge in 1997 to replace the southbound Keller Memorial Bridge. At the same time, the state refurbished what was then the northbound bridge, converting it to carry southbound traffic. Renovations to the current southbound span of the Hudson Memorial Bridge included sandblasting and resealing the metal and resurfacing, he said. Each span is operating as expected, he said, and more than 45,000 vehicles cross each span every day.

But figures from a federal database reported by The Associated Press on Thursday show that Alabama's roads and bridges have repair and maintenance needs that a federal study called "alarming."

As of Dec. 2, 102 of Alabama's 15,879 bridges had structural problems, causing them to not meet all federal standards, the AP reported.

While not of imminent danger to motorists, federal officials said the problem bridges need maintenance or replacement.

Federal data also rated 2,205 Alabama's bridges as functionally obsolete. Either they are too small for the type or number of vehicles that use them, or else they sometimes flood.

A 2005 study by the Washington-based Government Performance Project classified Alabama's roads and bridges as being in "alarming" shape. The state's $1.6 billion in back maintenance projects were growing by $50 million in new work annually, the AP reported.

Alabama bridges

According to the Federal Highway Administration, Alabama has 15,879 bridges. Twenty-seven percent of them are rated “structurally deficient” or “functionally obsolete.”

  • 2,102 bridges are rated “structurally deficient.”

  • 2,205 bridges are “functionally obsolete.”

  • 59 percent of Alabama’s bridges were built in 1967 (the year the Minneapolis bridge was built) or earlier.

  • The state has 1,169 interstate bridges. Two percent of Alabama’s interstate bridges are rated structurally deficient, and 18 percent are rated functionally obsolete.

  • According to a University of Alabama study, the state spends $50 million a year to maintain bridge safety. It needs $4 billion over the next 10 years to repair and replace obsolete and structurally deficient bridges.

    - Eric Fleischauer

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