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Project of the Year (between €50M and €500M)

Chinatown Station of the Central Subway Program - San Francisco

Chinatown Station is one of three stations for the Central Subway Project, a north-south LRT extension. Chinatown is a vibrant commercial and residential district with the city’s highest population density. Chinatown station project was one of the most challenging engineering and underground construction projects in the U.S. due to its setting in narrow streets, historic buildings, numerous utilities and poor ground conditions.

The station's main elements are the Station Platform and Crossover caverns combined. The overall main cavern dimensions are 192m long by 16.7m wide and 13.1m high with an excavated cross section of 202m2, making it one of the largest Conventional Tunneling excavation in poor ground and soil-like materials in the U.S. The main station entrance and service facility are located off street and connected to the platform cavern via a Cross-Cut cavern. This enables the construction of the station cavern in two directions simultaneously, running as many as four operations.

Due to ground variability and the risk of Conventional Tunneling, a pre-support system comprised of grouted steel pipe arch canopies were provided and face bolts were used in the center drift. To protect adjoining buildings, including “the Mandarin Tower” and the historic Presbyterian Church, an instrumentation and monitoring plan was developed using multi-point extensometers, inclinometers, and Total Stationing. Compensation grouting was implemented to maintain the settlement in impacted structures to less than 12mm.