Location:
San Francisco, CA
Owner:
San Francisco Public Utilities Commission
Construction Cost:
$282,000,000
Role:
Preliminary Design, Final Design/Construction Documents, Geotechnical Characterization
Bay Tunnel
The Bay Tunnel project is part of the San Francisco Public Utilities Commission’s (SFPUC) master plan to upgrade the Hetch Hetchy Water System, which brings water from Yosemite National Park to the San Francisco Bay Area. This tunnel will extend 5 miles (8 km) under San Francisco Bay, replacing pipelines that are at the end of their useful life.
As the prime consultant, Jacobs Associates is providing tunnel design and construction support services for this challenging project. The tunnel will lie at depths ranging from 75 to 110 feet (23 to 34 m) in sandy and silty clays under high groundwater pressure and through a short section of bedrock. Due to these ground conditions, an earth pressure balance tunnel boring machine (TBM) will be utilized for excavation between two deep shafts. This is the first use of a TBM for excavation under San Francisco Bay. The tunnel will be lined with precast concrete segments followed by steel pipe, resulting in an internal finished diameter of 108 inches (2.7 m).
The Bay Tunnel’s alignment is located in the vicinity of a wildlife refuge and between two of California’s largest active faults, the San Andreas and the Hayward faults. As a result, Jacobs Associates has focused on a design that both addresses environmental concerns and assures serviceability in the case of a severe earthquake.