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Groundwater Lowering

Chinatown Station

Service Performed
Conceptual, preliminary, detailed design of underground caverns, egress tunnels and mined shafts; scheduling and cost estimating; risk management; specifications and tender. Onsite support during construction.
Estimated cost
$1,600,000,000
Commencement - Services
March 01, 2016
Completion - Services
March 31, 2018
Location
425 Market Street Suite 1700
San Francisco, CA 94105
United States
Geology description

The geology ranges from soft clay (Bay Clay) to stiff sands (Colma Sands) and competent to highly fractured rock (Franciscan Formation). The groundwater table is generally above the cavern springline.

Geology types
Description

Chinatown Station is the Northern Terminus of the Third Street Light Rail Project, which is located in a dense urban neighbourhood, underneath a busy street and directly adjacent to numerous old buildings, as well as one high-rise building. The station encompasses a Cut-and-Cover headhouse for passenger entry, three large station caverns and an emergency egress shaft. In order to minimise excavation volume and optimise cost and schedule, the ventilation ducts are located below the platform level, and routed into the headhouse.

Activity
Construction methods
Special Construction techniques
Tunneling under
Groundwater control
Groundwater Lowering
Tunnel length
2.7km
Excavation and support sequence of large urban cavern
Large urban cavern under construction
Excavation and support sequence - longitudinal section
Chinatown, San Francisco Dense Urban Neighborhood
Overall Station Layout, Headhouse and Caverns (Rendering by JV)
Station Cavern with Center Platform, Mezzanine and Ventilation Ducts
Proposed Mitigation Measures for adjacent Buildings
Complex 3D Finite Element Analyses
Project number
358E
Final cost
$1.6 billion USD
Completion date
Ongoing

Beacon Hill Station

Service Performed
NATM / SEM station design and construction supervision.
Estimated cost
$250,000,000
Commencement - Services
February 26, 2000
Completion - Services
December 28, 2007
Location
401 S. Jackson Street
Seattle, WA 98104
United States
Technical data

NATM Light Rail Station located 150 ft (46 m) beneath surface. Station complex includes central elevator/access shaft, concourse, opposing platform tunnels and cross passages. Platform Tunnel Section: 36 ft w x 31 ft h; Platform Tunnel Area: 925 sqft (86 m²); total Station Excavation Area: 63,000 sqft (5853 m²).

Geology description

Over-consolidated glacial clay and till with fracutured zones. Intermittent sand and silt layers with perched groundwater.

Geology types
Description

The Beacon Hill Tunnels and Station are part of the 22.5km initial segment of the Sound Transit Central Link Light Rail Line that will establish a high capacity commuter connection from downtown Seattle to Tacoma. The 1300m running tunnel under Beacon Hill will be mined by Earth Pressure Balance Machine (EPB), while the deep mined Station will be constructed using slurry walls and the New Austrian Tunneling Method (NATM), referred to as Sequential Excavation Method (SEM) for this project.

Activity
Bid cost
$280,000,000
Final cost
$280,000,000
Construction methods
Tunneling under
Groundwater control
From within the Tunnel, Groundwater Lowering, Vacuum Lances
Max Overburden
Min:120 Max:140
Beacon Hill Station layout
Tunnel excavation under way
3D rendering of Beacon Hill Station complex
Platform tunnel cross section
Schwind Thomas
Installation of Vacuum Dewatering
Rendering of Beacon Hill Station
Project number
325
Final cost
$280 million USD