The Black Hawk Bridge in the small town of Lansing, Iowa got some recent attention when an 8-in. (20.3 cm) crack was discovered in the floor beam during a routine inspection.
The inspection took place during the morning of Aug. 17. By the afternoon, the bridge was closed to all traffic and the Iowa Department of Transportation (IDOT) bridge crews were called in, along with consultant firm Wiss, Janney, Elstner Associates Inc. (WJE). WJE is headquartered in Northbrook, Ill., and provided design services for the repair.
The Black Hawk Bridge, named after the famous Indian Chief Black Hawk, was built in 1931 by the McClintic-Marshall Company of Chicago, Ill. It is 1630.7 ft. (497 m) long and 21 ft. (6.4 m) wide, with three main spans and six approach spans.
“This bridge is among the most unusual and significant large scale cantilever truss bridges in the country, on account of its excellent historic integrity, relatively old age, increasing rarity, and unusual design,” noted Nathan Holth, webmaster of www.historicbridges.org. Located in one of the most beautiful and photogenic settings imaginable, with a small town on the Iowa side, and expansive flood plains on the Wisconsin side, all contained within a large and impressive river valley.
The bridge functioned as a toll structure until flooding washed out some of the approach spans over the Wisconsin bottoms in 1945. It stood unused for several years until the approaches were re-constructed and the bridge re-dedicated in May 1957. The Black Hawk Bridge now carries traffic as a free bridge, in essentially unaltered condition. (www.iowadot.gov/historicbridges)
Having the bridge closed caused quite a stir for local traffic.
“We get a lot of traffic from Wisconsin over the bridge,” said Mayor Don Peters. “The bridge has been a lifesaver for our city.”
Mayor Peters saved tourists and factory workers a 70-mi. round trip commute by scheduling a ferry service to run while the bridge was being repaired. Mississippi Explorer Cruises, owned and operated by local Jack Libbey, ferried folks across the river from 6:30 to 7:30 a.m., and again from 3:30 to 4:30 p.m.
The Black Hawk Bridge — the only connection between Iowa and Wisconsin for 35 mi. in any direction — was closed for a total of six days. The repair cost $25,000.
“The impact of the closure was immediately evident on the local shops and restaurants that depend on the bridge,” noted Mayor Peters.
Since the mid-50’s, other repairs have been made to this bridge due to damage caused by passing barges. In 1993, IDOT installed what they refer to as a “dolphin”; a circular pier located upstream of the bridge to serve as a barrier against barge impacts.
“Just upstream of the bridge, there is a sharp bend in the river’s navigation channel.
“Downstream barges have hit the bridge piers when they turned too sharply in anticipation of the bend,” explained Dave Little, IDOT Assistant Engineer District 2. Since the dolphin was constructed, there have been no recorded impacts with the bridge pier it is shielding.
IDOT has plans to install a second dolphin to shield another pier toward the Wisconsin side of the bridge. This project will be let in June 2012.
The bridge also is scheduled to be repainted in 2012, and will receive its annual cleaning.
Not only does the Black Hawk Bridge serve an important function, but it is a historical and cultural landmark to Lansing residents — one that they plan to hold onto for many years to come.
Holth explained the rapid rise in significance of the surviving cantilever truss bridges in the United States. “Quite often, a bridge owner will demolish a historic cantilever bridge and replace it with a cable-stayed bridge, with no heritage value or engineering significance.”
“There are ample locations to view the bridge from numerous angles, including a truly spectacular and unique view of the bridge from the Mount Hosmer lookout in Lansing. This is a bridge that must be seen in person to be truly appreciated,” expressed Holth. CEG
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