Minnesota gets aggressive when scrutinizing critical bridges

Associated Press Photo — Minnesota transportation workers, shown here earlier this week at the Highway 43 Bridge at Winona, have been busier than usual with bridge closures this year.

The Associated Press

6/5/2008

ST. PAUL. Minn. — Minnesota transportation officials have closed three busy bridges since March, hoping motorists will put up with the hassle to avoid the possibility of another deadly bridge collapse.

The aggressive approach follows the deaths of 13 people in last year's failure of the Interstate 35W bridge over the Mississippi River. All three closures deal with compromised steel plates connecting bridge beams — identified by investigators as a key factor in the collapse.

Minnesota seems more willing than other states to throw up barricades even as engineers across the country take a harder look at steel truss bridges with similar designs.

"We're sort of in a learning process, I'll have to admit that," said Minnesota state bridge engineer Dan Dorgan at a news conference on Wednesday.

On Tuesday, state officials closed the Highway 43 bridge over the Mississippi River in Winona — the same bridge featured on a new postage stamp commemorating Minnesota's 150th birthday — after an inspection found rust and corrosion on several gusset plates, or connector plates, on the span's Wisconsin end. One of the plates showed slight bending, Dorgan said.

Transportation Commissioner Tom Sorel said the Winona bridge's gusset problems are different from the design flaw of too-thin plates on the I-35W bridge.

Closing the 67-year-old Winona bridge comes at no small cost to those who use it. Detours to the nearest river crossings take them 50 or more miles out of their way. Sorel wouldn't predict how long the bridge will stay closed and said there's no decision yet on whether to repair or replace it. In the meantime, officials are considering ferry service, water taxis and pedestrian access to the bridge.

Two other bridges have been closed entirely or in part since March.

The Blatnik Bridge connecting Duluth and Superior, Wis., has had lane closures while crews reinforce gusset plates that didn't meet load requirements at eight spots on the bridge. It remains partly closed today.

In St. Cloud, state officials opted to replace the Highway 23 bridge over the Mississippi even though one of their engineering consultants advised them that they could probably get by with repairs. The bridge has been closed since March and work has begun on a replacement.

The National Transportation Safety Board shows 12,612 truss bridges nationwide as of January. Of those, 466 are steel deck truss bridges like the I-35W span that fell.

Bridge engineers around the country are paying more attention to gusset plates and original bridge plans than they did before the collapse, but that doesn't seem to be translating into an increase in closures outside Minnesota, said Ken Kobetsky, program director for engineering at the American Association of State Highway and Transportation Officials.

Missouri closed a steel truss bridge near St. Louis for a weekend last August after a regularly scheduled inspection found rust building up behind a splice plate connecting two beams, said Missouri bridge engineer Dennis Heckman.

"It's a more heightened awareness now," he said. "It's not that we're closing more bridges than we used to, at least in Missouri."