Central Subway

The San Francisco Municipal Transportation Agency - MUNI
PB / Kwan Henmi / Michael Willis JV
$1.6 billion USD
March 2010 — May 2012
Services performed
Preliminary and final SEM tunnel design at Chinatown Station.
MUNI planned a 2.7 km underground extension to the Third Street Light Rail Project. The underground section would start near Bryant Street, run along Third Street, cross under four BART Tunnels at Market Street and continue under Geary and Stockton Streets to Clay Street. Dr.Sauer and Partners was the designer for the SEM Tunnel Structures at Chinatown Station and prepared detailed excavation and support sequences as well as procedures for the construction of the large caverns and final design documents for SEM construction.
The geology ranges from soft clay (Bay Clay) to stiff sands (Colma Sands) and competent to highly fractured rock (Franciscan Formation). A considerable part of the tunnel alignment is below the groundwater table.
San Francisco, USA


  • Tunnelling in dense urban environment
  • Large caverns
  • NATM/SEM, TBM and cut-and-cover structures, quality control, safety inspection, documentation

Route Map

Station layout, headhouse and caverns (Rendering by JV)