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Alameda Siphon #4 (WSIP)

Project Update

The major construction activities for a fourth seismically-designed pipeline and other improvements for the Alameda Siphon No. 4 project are now complete. Recently, crews also completed the installation and in-service testing of the instrumentation, control and security system for the project as well. This project will ensure the water system performs properly, and water can be delivered to customers after an earthquake. The project is expected to reach final completion early this summer.

Project Description
The Alameda Siphon No. 4 Project extends approximately 3,000 feet from the Alameda East Portal across both the Calaveras Fault and Alameda Creek to the Alameda West Portal.
The project consists of:

  • A 66-inch diameter welded steel pipeline with 310 feet of a seismically-designed special trench thicker-walled pipe in the fault rupture zone, and a tunnel crossing under Alameda Creek.
  • A 96-inch diameter “blending structure” that consists of a pipe and valve manifold near the Alameda West Portal that will blend water from the Sunol Valley Water Treatment Plant and Hetch Hetchy, so the existing and new Irvington Tunnels will receive a uniform quality of water.
  • Other ancillary project components include the following: new valves on the existing siphons, ventilation improvements, chemical injection facilities, overflow pipe, road improvements at the intersection of Calaveras Road for construction access, and improvements to the bridge crossing Alameda Creek.

Project Information

    August 2009
    August 2012
  • COST
    $65 Million

Additional Information

The information shown reflects the current forecast information published in the latest WSIP Quarterly Report.


Need More Information? Contact Us

Betsy Lauppe Rhodes
Phone: (415) 554-3240 or