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451 Minnesota Bridges "Functionally Obsolete"

August 02, 2007 By Conrad deFiebre, Transportation Fellow
The Interstate Hwy. 35W bridge that tragically collapsed into the Mississippi River Wednesday evening was one of 1,135 road spans in Minnesota rated as "structurally deficient" by the federal government.

That's 8.7 percent of the state's 13,008 bridges, 20 feet or longer, that are subject to annual inspections. Another 451 spans are considered "functionally obsolete." Included in the total are 65 bridges that are more than a century old.

Minnesota's aging and inadequate bridges present a huge fiscal challenge to a state that has largely neglected its vital transportation infrastructure for the past two decades. State officials have known of the I-35W bridge's structural shortcomings since at least 2001, but budget constraints dictated that it was not considered for major repairs until at least 2020.

"It takes money, and we haven't passed any major funding bills for a long, long time," said Rep. Bernie Lieder, chairman of the state House Transportation Committee. "The problem's been building up and we aren't really addressing it."

Lieder, a retired civil engineer, said the doomed bridge's rating of 50 on a structural stability scale of 120 in a 2005 federal inspection report made it "one of the toss-ups" for accelerated funding. Bridges rated below 50 get more immediate attention, he said.

The I-35W bridge opened in November 1967, just one month before the collapse of a highway span on the Ohio River claimed 46 lives and prompted new engineering and inspection standards. That means the 141,000 Minnesota drivers who crossed the Mississippi River bridge daily were stuck with an early-1960s design that lacked the extra structural supports now required.

In 2001, University of Minnesota civil engineers who studied the bridge for the state Department of Transportation noted that its approach spans exhibited "several fatigue problems, primarily due to unanticipated out-of-plane distortion of the girders" - twisting, Lieder said.

"Concern about fatigue cracking in the deck truss is heightened by a lack of redundancy in the main truss system," the engineers reported, adding: "Fatigue cracking of the deck truss is not likely. Therefore, replacement of the bridge, and the associated very high cost, may be deferred."

Now replacement of the bridge can no longer be deferred, although that will take years of planning and construction as well as tens of millions of dollars in state and federal outlays. Meanwhile, Twin Cities commuters can expect years of increased traffic snarls beyond the area's already high levels of congestion.

Perhaps, though, the I-35W bridge tragedy will lead to the long-delayed roads and transit investments Minnesota needs. "I'm sure it will build support for it," Lieder said.

Related Story: Road, Bridge Investments Falling Ever Shorter Published on July 12, 2007

How to Help:
If you want to help, please visit the Twin Cities Red Cross online at or call them at 612-460-3700.  They currently need both blood and financial donations.  Memorial Blood Centers are also calling for blood donations; you can contact them at 1-888-GIVE-BLD.

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