Granite Launches Major Rehabilitation of Chicago’s Historic Lake Street Bascule Bridge
Granite one of the nation’s leading infrastructure contractors, has officially commenced construction on a transformative $138 million rehabilitation project for the historic Lake Street Bascule Bridge in Chicago, Illinois. The project, awarded by the Chicago Department of Transportation (CDOT), marks a significant milestone in the ongoing modernization of Chicago’s aging infrastructure while preserving one of its most iconic engineering landmarks. The initiative, funded by CDOT, was added to Granite’s first quarter Capital Allocation Plan (CAP) and demonstrates the company’s growing engagement in complex urban infrastructure projects across the Midwest.
A Landmark with a Century of History
First opened to traffic in 1916, the Lake Street Bascule Bridge stands as a symbol of Chicago’s innovative spirit in both architecture and engineering. Designed as a double-deck, double-leaf trunnion bascule bridge, the structure was a groundbreaking feat of early 20th-century design. It was the world’s first double-deck trunnion bascule bridge, a movable bridge type that allows each deck to lift independently, using a system of counterweights and gears to enable river navigation below while maintaining efficient road and rail connectivity above.
Located in the heart of downtown Chicago, the bridge carries immense civic and transportation importance. The lower deck accommodates vehicles, pedestrians, and Chicago Transit Authority (CTA) buses, while the upper deck supports the CTA’s Green and Pink Line trains, forming a vital corridor for both commuters and river traffic. For over a century, the bridge has been a critical link in Chicago’s bustling transportation network, enabling millions of daily journeys while serving as an enduring reminder of the city’s industrial heritage.
Preserving the Past While Building for the Future
Granite’s rehabilitation of the Lake Street Bridge is designed to honor its historical legacy while upgrading it for modern performance, safety, and resilience. The company’s scope of work includes full replacement of the existing double-decked trunnion bascule bridge that spans the Chicago River, ensuring that the new structure matches the aesthetic and architectural style of the original 1916 design.
The project aims to preserve the bridge’s historic façade, maintaining its characteristic steel truss framework and the distinctive architectural detailing of its bridge houses—the operator cabins that flank the riverbanks. These bridge houses, considered historic landmarks in their own right, will undergo meticulous restoration work to maintain their period-correct appearance while being upgraded to modern standards of functionality and safety.
In alignment with CDOT’s commitment to sustainable and historically sensitive construction, Granite will employ modern materials and methods that both enhance the bridge’s performance and extend its lifespan. The project’s focus on heritage preservation is in keeping with Chicago’s long tradition of blending old-world craftsmanship with cutting-edge engineering.
Comprehensive Rehabilitation Scope
The Lake Street Bascule Bridge rehabilitation is far more than a routine maintenance effort—it is a full-scale modernization of an intricate and mechanically sophisticated structure. The project involves several major components:
- Complete replacement of the existing double-deck trunnion bascule bridge across the Chicago River, including both the superstructure and critical substructure elements.
- Rehabilitation of the substructure, which includes repair and strengthening of piers and foundations that have been subject to over a century of use and environmental wear.
- Replacement of the CTA track system on the upper bridge level, ensuring continued safe and reliable service for the Green and Pink Lines.
- Upgrades to mechanical and electrical systems, including the bridge’s complex gearing, motors, and control systems that enable the bascule leaves to lift and lower for river traffic.
- Restoration of the historic bridge houses, maintaining their distinctive architectural character while integrating updated operational and safety technologies.
- Installation of new lighting, walkways, and protective systems to enhance safety for pedestrians, operators, and maintenance crews.
Each aspect of the rehabilitation has been planned with precision to balance the bridge’s historical preservation with contemporary performance needs, ensuring it remains functional and visually consistent with Chicago’s architectural heritage.
Engineering Challenges and Innovation
One of the defining features of this project is the innovative construction approach that Granite will employ to minimize disruption to the public and the city’s transit systems. The construction of the new bridge leaves—the two massive sections that pivot upward to allow ships to pass—will take place off-site, in a controlled environment. Once completed, each leaf will be transported to its final location on the Chicago River using a carefully coordinated “float-in” procedure.
This method, which involves floating the completed bridge leaves on barges and installing them in place during brief river closures, significantly reduces the environmental and logistical impact of on-site construction in a dense urban setting. It also ensures the highest possible quality control by allowing Granite’s engineers and fabricators to work under optimal conditions before installation.
To enable the replacement of the upper-level rail components, two major service outages are planned for the CTA Green and Pink Lines: one 12-day outage in Fall 2026 and another in Spring 2027. During these periods, Granite’s team will work around the clock to remove and replace key structural and track components.
Throughout construction, Granite must also adhere to federal regulations and United States Coast Guard requirements, maintaining operational capability of at least one bridge leaf at all times to ensure that maritime traffic on the Chicago River remains functional. This adds a layer of complexity to the project, demanding precise sequencing and coordination among multiple stakeholders, including CDOT, the CTA, and the Coast Guard.
A Collaborative Effort for Chicago’s Infrastructure Future
“This collaboration with CDOT to rehabilitate one of Chicago’s century-old, iconic movable bridges underscores Granite’s strategic commitment to the Chicago market,” said Michael Punches, Granite’s Vice President of Regional Operations. “By leveraging our specialized expertise in movable bridge rehabilitation, we continue to deliver lasting value to the City’s infrastructure.”
Granite has a long history of delivering high-impact transportation and civil infrastructure projects across the United States, particularly those involving complex movable bridges, heavy civil structures, and urban reconstruction. The Lake Street Bascule Bridge project aligns perfectly with the company’s expertise in complex mechanical bridge systems and urban construction logistics, while reinforcing its dedication to community value and long-term resilience.
Economic and Community Impact
Beyond its engineering significance, the rehabilitation of the Lake Street Bridge represents an important economic and civic investment for Chicago. The project will support local labor and trade unions, create construction and engineering jobs, and enhance the reliability of public transportation—a vital benefit for residents and commuters who depend on the CTA’s elevated train system.
When completed, the revitalized bridge will provide smoother, safer travel for vehicles and pedestrians, while ensuring uninterrupted service for CTA trains. It will also reduce maintenance costs for the city in the long term and strengthen Chicago’s broader goal of revitalizing its historic riverfront infrastructure.
The project also symbolizes a broader trend toward infrastructure renewal in the United States, as municipalities modernize century-old assets to meet 21st-century demands. With federal and local funding increasingly focused on sustainability and preservation, the Lake Street Bridge serves as a model for how historic engineering icons can be renewed without losing their character.
Project Timeline
Construction officially began in October 2025, following months of detailed planning and coordination among Granite, CDOT, and various engineering consultants. The project is expected to reach substantial completion in December 2027, after which the bridge will re-open to full service for vehicles, pedestrians, and trains.
Upon completion, Chicago will once again have a fully restored and operational Lake Street Bascule Bridge—a living testament to both the city’s historic ingenuity and its modern commitment to engineering excellence.
A Bridge Between Eras
The rehabilitation of the Lake Street Bascule Bridge is more than an infrastructure upgrade—it is a bridge between eras. As Granite brings new life to this century-old landmark, the project symbolizes Chicago’s enduring ability to balance preservation with progress. Through this ambitious effort, Granite and CDOT are ensuring that the bridge continues to serve the people of Chicago for another hundred years—standing tall as both an engineering triumph and a timeless piece of the city’s skyline.
