Archive for Thursday, August 16, 2007

U.S. 56 bridge is ‘fine,’ says KDOT

August 16, 2007

It may score low on the scale, but the U.S. Highway 56 bridge at the west edge of Baldwin City isn't dangerous, according to highway officials.

In the wake of the Minneapolis bridge collapse Aug. 5 that killed at least nine people, bridges around the country are getting a closer look. That includes the small bridge that crosses Tauy Creek on the highway. On a scale of 100, it has an 11.5 rating, the lowest in the county. But, there are many factors that go into that rating.

"To summarize, even though the structurally deficiency rating for this bridge is low, this bridge is structurally sounds and poses no dangers to the traveling public," said Kim Qualls, Kansas Department of Transportation spokesman. "There are currently no plans to replace this bridge in at least the next four to five years."

The bridge is a reinforced concrete slab and was built in 1929. That's the biggest strike against it as far as ratings. And, according to Qualls, the structurally deficient tag doesn't mean its crumbling.

"Structurally deficient is a (federal) term that defines a bridge inadequate to carry today's legal loads, whether by obsolete design standards, structural deterioration or waterway inadequacy," she said. "KDOT can have a technically structurally deficient bridge and there will be nothing wrong with it.

"The rating will be due to the design type," said Qualls. "For example, if a bridge was designed in the 1920s when a 5-ton load was considered a big load, it could still be on the state system and in good shape. But, it was built before today's heavier loads, so we would post a weight limit on the bridge. The Tauy Creek bridge is a perfect example of this."

Because the bridge was built in the '20s its mostly the design capacity that's at issue. But, there are other factors.

"The rating is greatly affected by the limited geometric elements of the bridge, including the bridge deck width and the approach width -- or pavement leading up to the bridge itself," she said. "The detour length that would be needed should this bridge be replaced and the average daily traffic counts on the bridge have impacted the low rating as well.

"Since the bridge was designed for lighter loads, this fact too has contributed to the lower sufficiency rating," said Qualls.

City Administrator Jeff Dingman was surprised to hear about the bridge. He is also hoping that KDOT will agree to a walk/bike trail plan the city has in the works that would use the bridge as a safe underpass to get across U.S. 56.

"I'm not sure what to think about it," Dingman said of the KDOT information about the bridge. "I think if we can get committed to a project to put a north-south trail system in through there, with KDOT participating via the Transportation Enhancement grant program, there would be some consideration to replacing that structure.

"I can't say for sure though," he said. "That's assuming a lot, that we have a project well enough defined to follow through with engineering and design, and then that we have the

desire/ability to pay for it."

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