Central Subway

Mining of the Chinatown station

transparent spacer image Above: The completed tunnel at the portal at 4th St., under I-80. Below: Excavation of the Yerba Buena/Moscone Station has reached the invert. Bottom: construction at Stockton and Market.
Yerba Buena Moscone Station Construction
Market Union Square station construction


The Central Subway Project will extend the Muni T-Third line north from Fourth and King streets to Chinatown. The route will move along Fourth Street, through a tunnel near Harrison Street, beneath Market Street, and un­der Stockton Street to the intersection of Stockton and Washington streets. With stops in SoMa, Yerba Buena/Moscone Center, Union Square, and China­town, Central Subway will greatly improve transit access for the residents of one of the most densely populated neighborhoods in the country, provide a rapid transit link to a burgeoning technology and digital-media hub, and im­prove access to a premier commercial district and tourist attraction.

The baseline budget for the project, led by the SFMTA, is $1.578 billion. A joint venture of Barnard/Impregilo/Haley finished work on the $233 million tun­nels contract in 2015 on time and $16 million under the baseline budget. Since then, the focus of construction shifted to the stations and systems contract. With 27 percent Disadvantaged Business Enterprise participation, contractor Tutor Perini is building three underground stations, one surface station, and the systems needed to support the subway extension.

The Transportation Authority has contributed nearly $150 million in Prop K half-cent local transportation sales tax funds, State Transportation Improve­ment Program funds, and other funds to the project. Transportation Authori­ty staff and project delivery oversight consultants will continue to work closely with the SFMTA as the project continues through the construction phase.




As of April 30, 2018, the Central Subway Project was 77% complete. Tutor Perini, the contractor for the $848,036,307 (including $8,359,907 in change orders to date) Stations and Systems contract is proceeding at all four station locations. At the Chinatown Station, (CTS) the headhouse excavation and the mining of the station cavern were completed on February 16, 2018, a major project milestone. Waterproofing installation of the platform cavern is underway. The mud slab has been installed at the CTS headhouse and the invert slab is being constructed throughout the platform cavern.

At the Union Square Station, (UMS) work continues on the major structural concrete for the station box and at the station headhouse on the Union Square garage, together with fireproofing for struts and roof beams. The contractor continued placing concrete for ventilation shaft walls and fireproofing for struts and roof beams at the Concourse level. Rough-in for fire sprinklers continues.

Meanwhile, at the Yerba Buena/Moscone Station, (YBM) where the major structural elements and station box have been completed, work is progressing on mechanical, electrical and plumbing systems. For the Surface Station (at 4th and Brannan Streets) and Systems package, work has been completed on the special trackwork at 4th and King Streets, the 78 in. sewer reconstruction, and the 48 in. sewer installation. The trackwork slab and plinth installation is underway and track is being installed along the tunnels. Street pavement renovation is also underway. The current schedule forecast indicates a revenue service date of December 2019.


  • Extend the north-south corridor of Muni's Metro System
  • Provide shorter travel times for passengers
  • Relieve congestion on the Stockton Street corridor
  • Provide connectivity to a future Geary line.


Date and Milestone

Construction: Jan 2010–Feb 2019
Startup and Commissioning: Mar 2018–Sep 2019
Revenue Service: Sep 2019