The Chinatown neighborhood of San Francisco is home to 10,000 residents and has long been one of the most densely populated neighborhoods in the country not served by an underground transit system until the opening of the SFMTA Central Subway extension project in early 2023. Stockton Street serves both as a bustling commercial and retail center, and a thoroughfare for the city’s bus lines and suffered from heavy congestion. The Central Subway extension provides residents and visitors to Chinatown with a reliable and convenient public transportation alternative and links this vibrant neighborhood to the rest of the city.
Due to the existing BART and Muni underground crossings at Market Street and the slope on Stockton Street up towards Washington Street, the tracks at the Chinatown Station are over 100-ft below the sidewalk elevation. This creates one of the deepest excavations in San Francisco in a tight urban setting and presents challenges in terms of architectural layout and construction sequencing. Located at the heart of the Stockton Street retail corridor, the available area for construction staging was extremely limited.
One of the major architectural visions was to bring light into the deep station to improve the spatial experience of the transit users. This was achieved by placement of escalators and permanent cross-lot struts. With a small lot, we designed the permanent retaining walls to also serve as the temporary soil retention system to maximize usable plan area.
Customized Solution
- The Chinatown neighborhood of San Francisco has long been underserved by public transportation. The Central Subway extension into this densely populated neighborhood is a welcome relief to its residents, who have the lowest median household income in San Francisco per US Census data. This project showcases how structural engineering can improve the daily lives of the residents of Chinatown and bring visitors to the neighborhood by extending an underground transit network that efficiently links this area to the rest of the city.
- The deep excavation was a major constraint due to the various levels of existing train lines that cross at Market Street that our new line must go below, and the surface geometry that slopes up as one goes north on Stockton Street. Integrating the temporary soil retention system into the permanent slurry walls required much detailed coordination with the design and construction teams. Defining construction steps for Staged Construction Analysis demanded a deep understanding of construction practices and limitations for both deep excavation and tunnel construction. This work paid off with a design that improved the spatial experience of its users and streamlined construction, and enabled the realization of this project in a logistically challenging site.
Highlights
- Owner: San Francisco Municipal Transportation Agency
- Architect: Kwan Henmi
- Contractor: Tutor Perini
- Concrete shear walls, concrete moment frames, horizontal steel trusses and center-coring of the existing brick masonry walls.
Team
Paul Rodler
Senior Principal
Mason Walters
Senior Principal
Mei Kuen Liu
Senior Associate
Marco Scanu
Senior Project Manager