Thursday, November 15, 2012

Then & Now: Tunnel Lining

The existing Irvington Tunnel was built in the early 20th century and can no longer be taken out of service for repairs or maintenance without impacting the water supply to customers. The last time the old tunnel was inspected for maintenance was in 1966. Completion of the New Irvington Tunnel will allow us take the existing tunnel out of service for much needed maintenance. The new tunnel is designed to provide a seismically-strengthened or reinforced connection between water supplies from the Alameda Watershed to Bay Area customers

Here’s a quick look at tunnel construction then and now:

Then: In 1933, the existing Irvington Tunnel was lined with cast-in-place concrete. The average cost of house was $5,750, IT’S-IT Ice Cream was gaining popularity at San Francisco’s Playland-at-the-Beach, and baseball by the Bay was played at Seals Stadium

Now:  The New Tunnel will be lined with a total 18,660 feet of welded steel pipe..  After the pipe is installed, the pipe will be lined with cement mortar finish to protect the steel pipe from rusting, so the tunnel will serve drinking water for future generations.

At 102-inches (8.5 feet) in diameter, the pipes are the final liner of the new tunnel, through which the pristine drinking water from the Hetch Hetchy Reservoir and our East Bay Watershed will flow to the San Francisco Bay Area.

Just in case you’re curious about how things compare in 2012:  The average price of a home is $295,300, Playland-at-the-Beach is gone but IT’S-IT is found at your local grocer, and the World Series Champion San Francisco Giants play at AT&T Park! 

Check out the previous entries in NIT’s Then & Now series:

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