|Official name||Zilwaukee Bridge|
|Carries||I-75 / US 23|
|Maintained by||Michigan Department of Transportation|
|ID number||73173112000B031 NB
|Total length||8,061 ft (2,457.0 m) NB
8,085 ft (2,464.3 m) SB
|Width||74 ft (22.7 m)|
|Height||125 ft (38 m)|
|Longest span||392 ft (119.5 m)|
|Number of spans||26 NB, 25 SB|
|Load limit||MS 22.5|
|Clearance below||36.5 m (120 ft)|
|Construction begin||late 1979|
|Construction end||September 19, 1988|
|Opened||December 23, 1987|
|Daily traffic||23,450 vehicles|
|Preceded by||Zilwaukee Drawbridge|
The Zilwaukee Bridge is a high-level, segmental concrete bridge spanning the Saginaw River in Zilwaukee, Michigan, approximately 5 mi (8.0 km) north of Saginaw, Michigan, United States. The current eight-lane structure, completed in 1988, is the second such bridge at this location, replacing a four-lane bascule bridge constructed in 1960. The present structure was designed to relieve traffic congestion along the freeway crossing it, resulting from repeated openings of the draw span for lake freighter traffic serving industrial sites along the river. The Zilwaukee Bridge is approximately 8,000 feet (2440 m) in length and rises 125 feet (38 m) at its highest point.
While the need for a replacement of the original structure became acute soon after it was completed, the construction of the current structure was also plagued with difficulties.
Construction began in 1979 with an expected completion date three years later; however the bridge would not be available for traffic for nine years. The initial budget of $79 million was exceeded by $48 million. In 1982, with the bridge two-thirds complete, a 150-foot (46 m) long, 6,700-ton (6,070 metric tonnes) segment was not properly counterbalanced and sank five feet (1.5 m) out of alignment while rising 3.5 feet (1.1 m) on the other end, cracking a pier footing in the process. Once repairs were made, a new contractor was hired to complete the bridge once the initial contractor (Stevin Construction) and the state agreed to terminate their contract in exchange for both sides dropping their lawsuits over the accident. The new contractor developed a method of heating the concrete to allow construction during the winter. However, on some cold days these new sections could not be properly sealed against water infiltration, eventually leading to spalling as the water froze and expanded. Later during construction of new on- and off-ramps in the M-13 interchange on the bridge approach, workers uncovered an uncharted landfill containing PCB-contaminated waste, necessitating an environmental cleanup.
- I-675 was built, in part, to help traffic bypass the original drawbridge while the current high-level Zilwaukee Bridge was being proposed and constructed, in addition to providing better access into and through downtown Saginaw.
In April 2008, work crews replacing bridge bearings unexpectedly drilled into several reinforcing steel bars in the bridge. The $3.3 million project was further hindered when crews determined that more than 30 new bearings weren't designed properly. MDOT said crews are erecting a steel reinforcement on the exterior of the bridge to ensure that the structural integrity of the bridge remains sound. On October 21, 2008 the bridge opened up to north and south traffic again.
On December 7th, 2012 the Detroit News reported that a $70 million MDOT program would commence the following April to replace 154 of the bearings in question, rebuild 4 miles of I-75, replace the Janes Road bridge, and repair the CSX and Wadsworth Road rail bridges in the area. The work was slated for completion in 2015 and was expected to extend the life of the bridge to the year 2087.
- Staff (2010). "73173112000B031". National Bridge Inventory. Federal Highway Administration. Retrieved December 30, 2011.
- Staff (2010). "73173112000B032". National Bridge Inventory. Federal Highway Administration. Retrieved December 30, 2011.
- Bessert, Christopher J. (January 31, 2009). "In Depth: The Zilwaukee Bridge". Michigan Highways.
- Hyde, Charles K. (1993). "Historic highway bridges of Michigan". Detroit: Wayne State University Press. pp. 166, 172,. ISBN 978-0-8143-2448-6.
- Barber, Barrie (November 28, 2010). "Z-Bridge screw up remains under investigation". The Bay City Times.
- Seim, Charles (May 2008). "Why Bridges Have Failed Throughout History". Civil Engineering (Reston, VA: American Society of Civil Engineers) 78 (8): 64–71, 84–87. ISSN 0885-7024.
- Staff (May 11, 1987). The Zilwaukee Bridge: From the Beginning (Report). Michigan Department of Transportation. http://www.michiganhighways.org/indepth/zilwaukee_report.html.
- Zilwaukee Bridge at Michigan Highways