DES MOINES -- Laser technology will be used to record four of Madison County's six remaining covered bridges for historical reference and so they can be rebuilt if any more are destroyed.
Initially the 19th century timber bridges numbered around two dozen, but over the years wear and tear has caused most of them to fall apart, and at least one burned to the ground.
The structures, which became world famous because of the best-selling Robert James Waller novel "The Bridges of Madison County" and subsequent Clint Eastwood-directed movie, attract many tourists to the area.
The $50,000 laser-scanning project that begins Monday aims to produce an enduring chronicle of the much-loved bridges.
"It provides a good record that we can not only preserve the historical aspects ... but we could also provide a record that would be accurate enough to rebuild the bridge if we needed to," according to Mike Ritter, assistant director of the U.S. Forest Service's Forest Products Laboratory, which is leading the project.
Arson destroyed Madison County's Cedar Bridge in 2002. It was rebuilt by referring to old
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"We don't have any original plans of the bridges. We've looked, but no luck," Hagen said.
The boom box-sized scanner will shoot out an arc of laser that produces millions of dots, recording the shape of the bridges in two- and three-dimensional images, along with video, according to the company performing the procedure.
"Our scanners pick up every minute detail," said Penny Anstey, president of the Milwaukee-based company, SightLine.
"We will have nuts and bolts, the way the boards are going. We'll know if the boards are twisting, how is the bridge moving. We'll be able to pick all of this up," Anstey said. She said it would take five days to record the Iowa bridges.
The project, funded by the Federal Highway Administration, will record the Roseman Bridge, the Imes Bridge, the Hogback Bridge and the Cutler-Donahue Bridge. It will also capture a covered bridge in Cedarburg, Wis., and another in Zumbrota, Minn.
Brian Brashaw, program director for the Natural Resources Research Institute at the University of Minnesota-Duluth said laser scanning has been used on historic buildings as well as warehouses and factories, but this will be the first time it is used to record wooden structures.
"Our goal is just to understand how it works with timber bridges, and in this case, historic covered bridges," he said.
Tammy Ellwanger, the executive director of the Madison County Chamber of Commerce, said it was no surprise that the historic bridges continue to draw visitors from around the world.
"They have character," Ellwanger said. "The planks are smooth but show the indentations of the years of wear. When you look at the construction of the trusses, it's just amazing what they did and how that was constructed and that it has withheld all these years."
