Central Subway Project

The Central Subway Project is Phase 2 of the Third Street Light Rail Project, which will link Little Hollywood and Visitación Valley with downtown San Francisco. This project is vital to connecting the city’s civic, business, and cultural centers with the diverse communities along the corridor. Once complete, the project will improve service reliability and travel times, enhance transit connections, and provide economic opportunities and access to jobs for local residents. The Central Subway Project will provide 1.7 miles (2.7 km) of light rail service to the Financial District and Chinatown, as well as connect directly to BART and Caltrain, the Bay Area’s two largest regional commuter rail services.

As a member of the Central Subway Partnership program management/construction management team, Jacobs Associates is providing design oversight and cost estimate review during the final design phase, as well as construction management and inspection during the construction phase. The project requires tunneling in both soil and rock through the heart of downtown San Francisco. Subsurface conditions range from saturated alluvial soils and cemented sands to fresh and weathered bedrock, making this a challenging project.

Major design and construction issues include the need to minimize community disruption and manage tunneling risks. It is anticipated that earth pressure balance tunnel boring machines will be used to tunnel through the soil. Special tunnel connections and a mined station will be sequentially excavated (via the New Austrian Tunneling Method) using shotcrete and various presupport techniques. The project will require other advanced ground improvement and construction methods, such as deep concrete diaphragm slurry walls, secant pile walls, jet grouting, and compensation grouting. Traffic maintenance, complex utility relocations, and building protection measures are key project issues.