Longest U.S. bowstring bridge to be removed, stored; new owner sought

Yaeger (Kern) Bridge Credit: Minnesota Department of Transportation

The longest bowstring arch truss bridge in the United States is slated to come down this summer or fall, with a plan to store it for future use.

The Yaeger (Kern) Bridge, built in 1873 over the Le Sueur River between South Bend and Mankato townships in Minnesota, is in danger of falling down.

The townships had approved money to dismantle the wrought-iron bridge and sell it for scrap, but efforts by state and local officials appear to have saved the bridge, according to the Mankato Free Press.

Under the plan, the bridge will be dismantled and stored until the Minnesota Department of Transportation can find a new home for it, the Free Press reports. Most of the funding for the project will be left over federal grant money from another bridge project in the state. The agency has 10 years to find a new home, after which the bridge could be disposed of. Some hope it can be used in a park or other public location as a pedestrian bridge.

The cost of removing the bridge and putting it into storage is estimated at $340,000, and funding is available to cover 80 percent of the cost to restore and move it to a new location, should one be found, the Free Press reports.

Credit: National Park Service/Library of Congress

The single-span bridge was built soon after the Civil War by John Mahowald and the Wrought Iron Bridge Company of Canton, Ohio, for Blue Earth County for $6,000, according to an MnDOT bridge report. It remained in service into the automobile age until the 1990s when the road it was on was closed.

One of the exceptional aspects of this bridge is its 189-foot length. Such bridges are typically 50 to 130 feet long in the United States, according to the bridge report. The bridge is listed on the National Register of Historic Places and is the only bowstring bridge in the state. The only longer bowstring bridge left in North America is the Blackfriars Street Bridge in Ontario, Canada, at 216 feet.

Credit: National Park Service/Library of Congress

The trusses on the Kern Bridge consist of lattice girders as well as latticed top braces. The wooden deck is 20 feet wide.

The bowstring design was developed in 1840, with the first one built over the Erie Canal at Utica, New York, according to the report.

Once the Kern Bridge is removed, the Freeport Bridge in Decorah, Iowa, will be the longest U.S. bowstring bridge still in use. The 156-foot-long bridge was built in 1879, also by the Wrought Iron Bridge Co. It was moved from its original location and now stands in Trout Run Park in Decorah as a pedestrian-only bridge.

 

from Equipment World http://bit.ly/2ZIc0dF
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