News

Eaten Away, One Grain at a Time

The latest example of the adage that rust never sleeps would seem to be the Downtown Clybourn Street Bridge, which closed in July 2010 and isn’t expected to reopen until June 2011.

Photo by Michael Horne

Drivers’ demand for speed (and safety) prompts road salt to be spread even after mild snow flurries, but often with expensive consequences. According to a March story in Milwaukee Magazine (“The High and Mighty”), the corroding effects of road salt helped force the current rebuilding of Interstate 94. Simply put, salt makes the metal rust faster.

Was road salt a factor in the Clybourn bridge’s closing?

“Oh, yes. That’s the reason we shut it down,” says Cecilia Gilbert, communications manager for the City of Milwaukee Department of Public Works.

The department’s press release announcing the reconstruction was more circumspect, merely citing “the harsh river environment and continued deterioration of steel decking and support components” and not explicitly identifying road salt.

The bridge, built in 1968 immediately south of the I-94 span over the Milwaukee River, is now under an accelerated $3.96 million reconstruction contract after emergency repairs in 2009.

The bridge may have been more susceptible to saline attack than the freeway, largely a concrete structure. To keep the movable span light, the bridge’s decking is corrugated steel (like a cheese grater) that allows salt to creep into nooks and crannies, expediting the structure’s deterioration.

Plus, the open decking (unlike the freeway’s solid roadbed) permits much more salt to fall into the river below. As covered in a recent NewsBuzz story, a recent U.S. Geological Survey study found that runoff from road salt creates toxic conditions in most of Milwaukee’s waterways during the winter.

This article originally appeared on a website called Milwaukee Buzz News from Milwaukee Magazine. It is reproduced here with the permission of the author.