More than a century after its construction as the world’s first two-story bascule structure, Chicago’s historic Lake Street Bascule Bridge is being renovated using modern accelerated bridge construction techniques as part of a $138 million rehabilitation program.
Although the bridge has been closed to vehicular and pedestrian traffic since Granite Construction Inc. began work in October 2025, the upper level of the 360-foot-long Chicago River crossing has remained a critical connection to downtown for two lines of transit.
By assembling each 500-ton steel bridge leaf off-site and floating it by barge to the bridge site, the team aims to limit anticipated traffic service disruptions to just 12 days, substantially less than with conventional techniques. Installation of the first sheet will take place in mid-October, while the second will be placed next spring.
According to federal regulations, including those of the US Coast Guard, at least one bridge leaf must remain functional and operational throughout the project.
The granite approach echoes the contractors’ efforts to minimize railroad impacts during the 1914-16 construction of the structure around an existing two-story swing bridge.
16.3
Total in millions of US freight carloads and intermodal units for the first 32 weeks of 2026.
Source: Association of American Railroads
According to historical records, the two then-new swing leaves were built in the “up” position so that trains could continue to pass over the old bridge until that structure could be demolished. The bascule bridge was officially put into service in March 1916.
Although a well-known part of local history, the bridge has presented numerous challenges to the project team, which also includes construction manager HNTB and engineer of record AECOM. Many of them involve elements or conditions that are not taken into account during the design phase.
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“There have been figurative skeletons that continue to be uncovered as work progresses and elements are removed or uncovered,” says Granite project manager Jack Canale. The main challenges have involved additional replacement of structural steel components, as well as rebuilding the bridge’s control houses using the existing footprint of the original house, he notes.
“The project team had to work through missing design details coordinating with structural, mobile and architectural design disciplines to deliver solutions to the client while maintaining the overall project schedule,” adds Canale.
The entire rehabilitation project is expected to be completed by December 2027.
