Over the next five years, workers will bore a tunnel 100 feet below San Francisco Bay, to secure the city’s water supply from catastrophic failure in the event of a major earthquake.

The project, part of a $4 billion public works project to update the Hetch Hetchy water system, will be the first tunnel ever dug under the Bay. Once complete, the tunnel will protect the area’s water supply from earthquakes up to a 7.5 magnitude.

The scope of the tunnel, along with the magnitude of technology and machinery being brought to bear on the project, is awe-inspiring. A shaft more than 100 feet deep has already been opened. Workers have constructed a water treatment plant and a power substation. Beneath the ground, locomotives will ferry workers along tracks to the dig site, where a massive boring machine will carve a tunnel at up to 80 feet per da

From the Mercury News:

In the breezy open lands along San Francisco Bay, just east of Palo Alto, a historic engineering project is taking shape. And even though it sits in the heart of Silicon Valley, it has nothing to do with computers.

Dozens of construction workers in hard hats are welding together a massive, high-tech digging machine, transported from Japan on cargo ships in 65 crates, that by next month will begin carving a 5-mile-long tunnel under the bay’s floor to deliver drinking water to more than 2 million people.

“It’s like the giant worm in the movie ‘Dune,’ ” said Bob Mues, project manager for the San Francisco Public Utilities Commission, which is building the $313 million project.

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