Granite has started a $138 million rehabilitation of Chicago’s Lake Street Bascule Bridge — a century-old engineering marvel that still is an indispensable artery for cars, pedestrians, and mass transit across the Chicago River.
The CDOT-funded project, as documented in Granite’s first-quarter committed and awarded projects (CAP), is a major investment in the upkeep and modernization of one of the city’s most recognizable movable bridges. Originally built in 1916, the double-deck, double-leaf bridge transports vehicle and pedestrian traffic on its lower deck and Chicago Transit Authority (CTA) Green and Pink Line trains on its upper deck.
Under the rehabilitation scheme, Granite will completely replace the double-decked trunnion bascule span, replace substructure elements, and install new electrical and mechanical systems to power the movable bridge. The CTA tracks on the upper level will also be replaced, as restoration teams take measures to maintain the architectural character of the bridge houses and the supporting structure.
Granite Plans Off-Site Assembly to Limit Disruptions
To reduce outages, the new bridge leaves will be prefabricated off-site and floated in during two separate outages—one in fall 2026 and one in spring 2027. Each float-in will span about 12 days and discontinue CTA Green and Pink Line service. During the project, Granite must have a single bridge leaf available in service to meet U.S. Coast Guard and federal navigation requirements.
“Such a project with CDOT to restore one of Chicago’s century-old, historic movable bridges supports Granite’s strategic concentration in the Chicago marketplace,” Granite Vice President of Regional Operations Michael Punches said. “Through our technical expertise in movable bridge rehabilitation, we continue to deliver long-term value to the City’s infrastructure.”
Construction began in October 2025 and is expected to complete by December 2027. When completed, the refurbished building will improve Chicago’s transportation infrastructure while maintaining the looks and history of the world’s first double-deck trunnion bascule bridge.
Granite Construction, one of the largest diversified construction and materials companies in the United States, serves as a full-service civil contractor with major projects nationwide — including a $115 million runway rehabilitation and new Taxiway W construction at San Francisco International Airport (SFO), among other major projects.
Project Fact Sheet: Lake Street Bascule Bridge Rehabilitation
Project Value: Approximately $138 million
Client: Chicago Department of Transportation (CDOT)
Contractor: Granite Construction
Project Type: Bridge rehabilitation and preservation
Bridge Type: Double-deck, double-leaf trunnion bascule (movable) bridge
Original Construction: 1916
Work Scope:
Complete replacement of double-deck trunnion bascule bridge span
Rehabilitation of substructure
Replacement of Green and Pink Line upper-level CTA tracks
Upgrade of mechanical and electrical systems
Restoration of historic bridge houses and architectural features
Construction Technique:
Off-site construction and “float-in” replacement of bridge leaves
Two planned 12-day CTA service interruptions (Fall 2026 and Spring 2027)
Operational Need: Have one working bridge leaf at all times (U.S. Coast Guard compliance)
Start of Construction: October 2025
Projected Completion: December 2027
Location: Chicago, Illinois
