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 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.