The tunnel, which is expected to be five miles long and run under the bay near the Dumbarton Bridge from Menlo Park to Newark in the East Bay, is being built to ensure clean water from the Hetch Hetchy water system that currently supplies the region would continue to be provided in the event of a major earthquake or other disaster.
"The Hetch Hetchy water system is the lifeline for the entire Bay Area," SFPUC General Manager Ed Harrington said today at the groundbreaking for the first phase of the $347 million Bay Tunnel.
He was joined in Menlo Park by officials such as East Palo Alto Mayor David Woods and Art Jensen, the executive director of the Bay Area Water and Conservation Agency, according to a SFPUC spokeswoman.
Today's digging was the beginning of construction not on the actual tunnel, but on a 141-foot shaft that will serve as an entry and exit to the tunnel in Menlo Park.
An identical shaft is planned for Newark to provide access from the tunnel's east end, according to the utilities commission.
A tunnel-boring machine, which is being designed in Japan specifically for this project, is expected to be delivered next summer for on-site assembly, according to SFPUC spokeswoman Maureen Barry.
Once the machine arrives, it will be lowered down the Menlo Park shaft - which is expected to be completed by then - and begin digging the tunnel, which will be 15 feet in diameter and is planned to be submerged up to 100 feet below the water's surface at certain points, Barry said.
The tunnel is expected to be completed in 2015, and the project will likely require 575,000 hours of labor from construction workers, creating much-needed jobs in the region, according to SFPUC data on a website dedicated to the project.
Because there will only be two shafts providing access to the tunnel at each end of it, workers will have to commute up to four miles under the bay during the construction of the tunnel, Barry said.
"This is an unusual tunnel in that it doesn't have an intermediary shaft where people can come in (mid-way through the tunnel)," she said.
A golf cart will be lowered into the tunnel and left there to shuttle workers after a cage-like elevator is installed in the completed Menlo Park shaft, Barry said.
The same elevator will lower workers to the site each day as well as lowering the boring machine when it is assembled, she said.
The Bay Tunnel project is part of a massive overhaul of water systems in cities throughout the Bay Area that are served by the Hetch Hetchy Reservoir in Yosemite National Park, which provides water for 2.5 million people throughout the region, according to SFPUC data.
The sweeping $4.6 billion system upgrade, the Water System Improvement Program, was approved by voters in 2002 and is funded by a series of bonds that will be repaid through rates paid by utilities customers, according to Christina Kirby, a spokeswoman for SFPUC.
Sixty-one of the 86 projects that were earmarked under the plan have already been completed or are under construction, Barry said.
Completed projects include a multitude of new reservoirs in San Francisco and a nearly finished tunnel similar to the one that was started today, the Crystal Springs Tunnel, which runs underneath the bay just north of where the Bay Tunnel will be, Barry said.
"We're really investing in our water infrastructure so we have a seismically reliable system that we can use to deliver the highest quality water even after an earthquake or other major catastrophic event," Barry said.