The Irvington Tunnel, a crucial 78-year old component of the Hetch Hetchy Water System, will now have a sibling. The San Francisco Public Utilities Commission recently approved the New Irvington Tunnel Project to construct a new 3.5-mi-long tunnel parallel to the existing tunnel between the Sunol Valley south of Highway I-680 and Fremont, California.

Bid advertisement for the New Irvington Tunnel Project was originally scheduled for this week, with bids opening on Thursday, Feb. 25, 2010 with a contract award scheduled for early April 2010. Because of some needed time to complete revisions to the contract documents, the SFPUC says it now expects to advertise for bids later this month or mid-January 2010. 

Bids will be opened late February or early March with a contract award in April 2010. Construction is expected to begin in May 2010 with final completion by January 2014.

The SFPUC encourages all interested prime contractors to download prequalification packets at Prequalification is required to submit a bid on this project.

The tunnel will be excavated using conventional mining methods, including road headers and, in sections of hard rock, controlled detonations. The finished tunnel would be horseshoe shaped and have an internal diameter of approximately 8.5 ft to 10.5 ft. The estimated construction cost is $250 million.

The New Irvington Tunnel is part of the SFPUC’s $4.6 billion Water System Improvement Program (WSIP) to repair, replace, and seismically upgrade the Hetch Hetchy Water System’s aging pipelines, reservoirs, and dams.  WSIP includes more than 80 projects spanning seven counties from the Central Valley to Downtown San Francisco. 

“The New Irvington Tunnel project is among the most important components of the entire system to ensure that our 2.5 million customers will have water after a major earthquake,” says SFPUC General Manager Ed Harrington. “For this particular project to move forward is a significant moment for the water system and our customers.”

The new tunnel will provide an additional seismically-designed connection between water supplies from the Sierra Nevada Mountains and the Alameda Watershed to Bay Area water distribution systems.

Not only does it provide a seismically sound alternative to the existing tunnel, the new tunnel will allows the SFPUC to take the existing tunnel out of service for much needed maintenance and repair.

“This project is an enormous undertaking,” says Project Manager David Tsztoo. “The project resulted from an incredible collaboration of planners, designers, engineers, and other staff. This is an opportunity to use the latest technologies that science can offer to construct a conventional tunnel in challenging ground conditions.”

To speed up construction, the tunnel would be mined in four different directions simultaneously: from the Sunol Valley towards the west, from Vargas Road both to the east and west, and from Fremont to the east (limited to an approximately 500-ft “starter tunnel” at Irvington Portal work area only).

The city of Fremont receives approximately 30% of its drinking water from the SFPUC and the town of Sunol receives the majority of its water from the SFPUC system. The existing Irvington Tunnel is an important part of that water delivery system because it connects the water supplies from the Sierra Nevada Mountains and the Alameda Watershed to Bay Area water distribution systems serving SFPUC customers, including the city of Fremont.

Built between 1928 and 1930, the Irvington Tunnel has served a steadily increasing number of Bay Area residents to the point where the tunnel cannot be taken out of service for repairs or maintenance without impacting the water supply to customers. Because the tunnel is a crucial connection in the water transmission system, earthquake damage to the tunnel would severely impair the system’s ability to provide emergency water for health and fire protection for an extended period of time.