Project Background
The Central Subway project started in the late 1980s to improve transit on 3rd Street and in Chinatown. The T Third phase, which opened in 2007, connected several San Francisco neighborhoods. An expansion in 2013 added 1.7 miles to the line with four new stations in SoMa, Union Square, and Chinatown. The project cost $1.9 billion and received funding from organizations such as the Federal Transit Administration and the State of California. The subway aims to provide a faster and smoother transit experience in some of San Francisco’s most densely populated neighborhoods.
AECOM served as the Program and Construction Manager, overseeing the design and providing complete construction management and inspection services for the new subway. Major construction elements included tunneling, underground stations, utilities, trackwork, and systems integration. The project was completed on time and under budget, utilizing a successful risk management approach. AECOM also focused on building a positive construction experience with the community through extensive outreach and addressing stakeholder concerns.
Project Implementation
The project involved various stages such as building launch boxes for tunnel boring machines, excavating tunnels using tunnel boring machines, building stations, surface tracks, and systems, and installing a new track interchange. Notable achievements included completing major excavation for Yerba Buena/Moscone Station and Union Square/Market Street Station and pivoting work toward interior construction. These milestones are a testament to the project’s progress and success.
Tunneling
The Central Subway Project includes 1.7 miles of dual subway tunnels. Two 20-foot tunnel boring machines, named Mom Chung and Big Alma, began tunneling in 2013. Crews worked 24 hours a day, six days a week, excavating the tunnels at a pace of approximately 40 feet per day. These tunnels are vital for extending the T Third Line, improving transit, and reducing travel times during peak periods.