Skip to comments.Huge tunnel to be built under San Francisco Bay
Posted on 08/08/2009 12:21:14 PM PDT by csvset
Hoping to protect one of the Bay Area's main water supplies after the next major earthquake, construction crews will soon embark on a job that sounds like something out of a Jules Verne novel: building a massive, 5-mile-long tunnel underneath San Francisco Bay.
The project is believed to be the first major tunnel ever built across the bay.
Using a giant boring machine, workers will carve a 14-foot high corridor through clay, sand and bedrock from Menlo Park to Newark as deep as 103 feet below the bay floor. They'll then run a 9-foot-high steel water pipe through the middle.
"All the experts tell us that within the next 30 years, there is a 63 percent chance of having a major earthquake in the Bay Area," said Ed Harrington, general manager of the San Francisco Public Utilities Commission, which is in charge of the project.
"By building extra tunnels and strengthening our pipelines, it means we have much greater assurance that we'll have water after the next earthquake."
Bids on the tunnel will be advertised Friday.
Only 12 companies in the world are certified to perform the job, which is estimated to cost $347 million. Digging will start next spring on the Menlo Park shoreline just south of the Dumbarton Bridge, and head eastward, with work scheduled to be completed in 2015. An additional 16 miles of pipe connecting to the tunnel on either side of the bay also will be replaced.
The job is part of a $4.5 billion renovation by the San Francisco PUC to upgrade its water system. Commonly known as the Hetch Hetchy System, the network of tunnels, pipes and reservoirs delivers water 167 miles through gravity-fed pipes from Hetch Hetchy Reservoir in Yosemite National Park to Crystal Springs Reservoir along I-280 in San Mateo County.
The largest water system in the Bay Area, it provides some or all of the drinking water to 2.5 million people from North San Jose through the Peninsula to San Francisco, along with Fremont, Hayward and other parts of the East Bay.
Another agency, the Santa Clara Valley Water District, provides water to 1.8 million people in Santa Clara County from groundwater and the delta.
An engineering marvel, the Hetch Hetchy system was built following the 1906 earthquake, when San Francisco burned after its water system failed. Today, much of its equipment is antiquated and at risk of collapse in the next major quake.
The tunnel, for example, will replace two large steel pipes built in 1925 and 1936 that sit on the floor of the bay, and could easily break in a major quake, cutting off water for weeks.
"Being buried deep in stronger, tighter materials, there is much smaller vulnerability to being pulled apart from shaking and liquefaction," David Schwartz, a geologist with the U.S. Geological Survey in Menlo Park, said of the proposed tunnel. "From an engineering point of view, it's much stronger."
Schwartz noted that since the 1989 Loma Prieta Earthquake, a 6.9 magnitude event that killed 63 people and did $6 billion in damage, other Bay Area agencies have been hard at work.
Racing to beat the next earthquake, Caltrans has retrofitted dozens of freeway overpasses and is rebuilding the Bay Bridge. Pacific Gas & Electric has upgraded gas lines and substations. BART is retrofitting the Transbay Tube, a 3.6 mile-long cylinder that sits on the floor of the bay, connecting Oakland and San Francisco.
"The question is, can we get it all done in time?" Schwartz said.
Many of the region's hospitals have not been retrofitted. And thousands of old buildings, including homes and unreinforced masonry buildings, remain at risk.
USGS scientists say there is a 63 percent chance of a quake of 6.7 magnitude or larger hitting the Bay Area by 2036. Geologists are most concerned about the Hayward fault, which runs from San Jose to Richmond.
With that backdrop, the San Francisco PUC won approval from San Francisco voters in 2002 to upgrade its water system. Funding is coming from revenue bonds, financed by a near-doubling of residential water rates in San Francisco from $23 a month now to $40 in 2015, with similar hikes expected in other communities that receive Hetch Hetchy water.
The project also will rebuild pipelines, water treatment plants and Calaveras Dam, north of San Jose, over the next five years so that they can withstand a quake of up to magnitude 7.9 on the San Andreas fault and 6.9 on the Hayward fault.
Despite the sensitive politics of anything involving the bay, environmentalists did not oppose the new tunnel.
"The environmental effects of a tunnel would be less than if they built new pipelines across the marshes," said Florence LaRiviere, co-founder of the Citizens Committee to Complete the Refuge, in Palo Alto.
And the earthquake risks are real, so "it is entirely appropriate," she said.
Still, LaRiviere said she wants the PUC to remove the old pipes when the tunnel is done to restore the shoreline to its natural state. For now, the agency plans to leave them in place as a backup.
Contact Paul Rogers at 408-920-5045.
Modern Marvel show in the making.
What retard wrote this?
‘Huge tunnel to be built under San Francisco Bay’
I would imagine that this kind of work is anything but dull!
who is the GC?
| They're really hunting
deep-trench, burrowing gerbils.
They have longer tails . . .
As an engineer, I can see the need for the tunnel to protect the water system... but... THE COSTS!
By the time the usual costs overruns kick in, we're talking about $1,250 per INCH of tunnel! Just think about that - a month's of Bay Area rent, or a really nice laptop, or an INCH of tunnel. Something's out of whack here.
Seeing how the Dumbarton Bridge is right there, just about directly over the route in question, could they some how tie into it's infrastructure - and make the Dumbarton more quake-safe in the process - to save money?
You're right of course. Bay Area Rapid Transit (BART) trains run in a tunnel under the bay all day every day.
I could see how you could get bored.
From Menlo Park to Newark NJ. is a long way,
and all underground, better bring a book.
They should probably put in a rest stop under
Giant boring machine?
Contact Paul Rogers at 408-920-5045.
BART goes between Berkeley and SF by tunnel under the bay. That has always seemed pretty major to me.
Next project up is a bridge under the bay
you’re insulting retards there. First “its believed” and then theres the “across the bay”
Don’t know, must have missed the tunnel between england and france however, it is the largest tunnel in the bay area ever but there is no new science involved here.
Only by the ignorant, arrogant and delusional MainStreamMedia.
I guess they all think BART floats across the bay?
They probably outsourced this “news “ story to India
The guy simply hasn't a clue how to write.
Yeah, what the author really meant was, “I think it’s the first major tunnel, but I’m too busy to research it.”