Project–At–A–Glance

WSIP Region
Sunol Valley

Location
Sunol Valley, Alameda County

Construction Start
August, 2009

Construction Finish
October, 2011

Current Status
Design, Environmental

Project Cost
$74M

The three existing Alameda Siphons are pipelines that connect two tunnels and cross under the Alameda Creek in the Sunol Valley.  The siphons transmit water from both the Hetch Hetchy supply and the Sunol Valley Water Treatment Plant to the Bay Area, and thus provide an important link in the SFPUC Water Transmission system. They cross the Calaveras Fault in the Sunol Valley and are vulnerable to significant damage in a major seismic event.  This proposed project would ensure the continued delivery of water in case of a major seismic event on the Calaveras Fault by installing a new seismically-designed fourth siphon and other upgrades to the siphons facilities.

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 proposed project would consist 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” consisting of a pipe and valve manifold near the Alameda West Portal that will blend Sunol Valley Water Treatment Plant and Hetch Hetchy water so that the existing and new Irvington Tunnels will receive a uniform quality of water.
• Other ancillary project components, including 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.

Note: Schedule and cost information shown may vary from the 2007 Approved WSIP Schedule and Budget. The information shown reflects the current forecast information published in the latest WSIP Quarterly Report.