Hetch Hetchy Aqueduct: Big Fixes for Big Quakes

In 2002, San Francisco voters passed a ballot measure that would more than double their water rates by 2016. Why? Because the majority of those voters felt that spending billions of dollars to seismically retrofit and upgrade their water system was worth such an investment, especially when that water, most of which originated as Sierra Nevada snow melt 167 miles to the east, crosses three active faults on its way to Bay Area faucets.

Long overdue for an upgrade, much of the Hetch Hetchy water delivery system was built in the 1920s and 1930s, with large swathes of pipelines made of riveted steel that don't perform well during big earthquakes. At a cost of $4.6 billion, paid for by 2.5 million residents in Alameda, Santa Clara, San Mateo and San Francisco counties who rely on a blend of Hetch Hetchy and local reservoir water, the San Francisco Public Utilities Commission has been installing new pipes and employing state-of-the-art engineering elements designed to withstand, for example, a magnitude 7.1 earthquake on the Hayward fault. Water storage capacity is also being expanded under the Hetch Hetchy Water System Improvement Program. When the program is completed in 2016, a new tunnel built 100 feet below the San Francisco Bay will carry a steel water pipeline 5 miles from the peninsula to the East Bay. The nearly 90 year-old, earthen Calaveras dam in southern Alameda county will also be replaced, allowing the adjacent reservoir to finally be filled to its original storage capacity of 31 billion gallons.

Cameraman Josiah Hooper and Producer Sheraz Sadiq inside a concrete vault containing two Hetch Hetchy water pipelines.

When I was assigned this story, I knew that it would be a challenge to describe key features of the Hetch Hetchy Water System Improvement Program while also explaining the controversial history of the creation of the Hetch Hetchy aqueduct after San Francisco officials received federal permission in 1913 to flood and dam Hetch Hetchy valley in Yosemite National Park. Fortunately, my job was made much easier thanks to the assistance provided by the San Francisco Public Utilities Commission to film the construction activities on several key projects and to interview members of their staff, including General Manager Ed Harrington and the director of the Hetch Hetchy Water System Improvement Program, Julie Labonte.

It also helped to find an eloquent historian, Gray Brechin at UC Berkeley, to share with me the colorful history of Hetch Hetchy. He used to work as a TV Producer at KQED in the '80s, so he knew the importance of delivering concise and engaging soundbites.

The earliest and most vocal champion for Hetch Hetchy water was San Francisco Mayor James Phelan, who served from 1897 to 1902. Mayor Phelan hired an official at the USGS who was willing to moonlight on Phelan's behalf and file water rights to stretches of the Tuolumne River which flows through the Hetch Hetchy valley. Other water sources such as the American River, Sacramento River and even Lake Tahoe were also considered, and while they would have been cheaper to divert for the bustling metropolis of San Francisco, they wouldn't provide the quality of drinking water passing through the Hetch Hetchy valley in Yosemite National Park. Even President Theodore Roosevelt, a pragmatic conservationist who had camped with John Muir in Yosemite and established five national parks during his presidency, sympathized with San Francisco's request for the Sierra water flowing through Hetch Hetchy.


John Muir, a Scottish-born naturalist and founder of the Sierra Club, led the fight to save Hetch Hetchy. After the 1906 San Francisco earthquake, local publications like The Call pilloried Muir for refusing to go along with the city's plans to dam the valley. But Muir stood firm, writing passionately about the "cathedral" of Hetch Hetchy in national publications and trying to rally wealthy East Coast contacts and friends to his cause.

After Phelan left office in 1902, a corruption scandal involving his successor and a series of ineffectual, caretaker mayors didn't help the city's grasp for the waters of Hetch Hetchy. But the tide began to turn with the election of James Rolph Jr. in 1911 and President Woodrow Wilson's appointment of Phelan business associate and attorney, Franklin K. Lane, as Secretary of the Interior.

In 1913, Congress passed and President Wilson signed into law the Raker Act which allowed the city to move forward with the construction of the Hetch Hetchy water system. Muir died just a year later, embittered by the loss of his David vs. Goliath struggle to protect the valley.

Although we didn't have the resources to visit the reservoir created by the dam at Hetch Hetchy, we were granted rare access inside a new tunnel being adjacent to the Irvington Tunnel. This tunnel transports 95% of the system's water from Sunol to Fremont and it has not been taken out of service for maintenance and repair since 1966. When it's completed in 2014, the nearly 9-foot in diameter new Irvington Tunnel will offer an important level of redundancy to back-up a critical piece of Hetch Hetchy infrastructure.

A roadheader inside the New Irvington Tunnel which is being built alongside the old Irvington Tunnel to convey Hetch Hetchy and local reservoir water from Sunol Valley to Fremont.

"Redundancy" is a word that came up quite often during my research into the Hetch Hetchy Water System Improvement Program which, in addition to the New Irvington Tunnel, is building other infrastructure to ensure the continued delivery of 265 million gallons of water a day within 24 hours of a major earthquake. Take for example the new Bay Division Pipeline, a fifth regional pipeline that will extend for 21 miles, including a five mile-section bored under the San Francisco Bay that will connect to a seven mile-section of pipe extending from Newark to the New Irvington Tunnel in Fremont. The new 6-foot diameter, welded steel water pipeline will also extend nine miles from Menlo Park across the peninsula in San Mateo county. The last time a regional water pipeline was added to the Hetch Hetchy water system was Bay Division Pipeline #4, built in 1973 to carry water south of the San Francisco Bay alongside another regional pipeline completed 17 years earlier.

Two sections of trailing gear located next to the new Bay Tunnel construction site in Menlo Park.

So the overhaul of the Hetch Hetchy system will improve earthquake reliability, in part through redundant, back-up structures like the New Irvington Tunnel and the new Bay Division Pipeline #5. The upgrades to the water system will also boost storage capacity and, according to Julie Labonte and Ed Harrington, will also enable more efficient use of water through enhanced delivery of recycled water or groundwater. Given the likely increase in the Bay Area's population, and the effects of climate change on rainfall and Sierra snowpack levels, making sure the taps continue to flow with Hetch Hetchy water for future generations is a daunting task.

It's also a race against time. A stretch of Hetch Hetchy water pipelines cross the Hayward fault, an active fault which last ruptured in 1868. The past five earthquakes on that fault had intervals of roughly 140 years, so the fault could slip at any time, triggering a massive earthquake in a dense urban corridor. Having water on hand to drink and fight fires will be essential to minimizing the repercussions of a massive, magnitude 7.1 earthquake on the Hayward fault.


Since ancient Rome, water has been essential to the growth of cities and the expansion of empires. To paraphrase William Mulholland, the visionary engineer behind the 230-mile Owens Valley aqueduct that serves Los Angeles, "if we don't get it, we won't need it." Indeed, empires may come and go but the need for water will persist. The challenge today, it would seem, is how to continue to meet this need while upgrading these marvels of 20th-century engineering to adapt to a 21st-century landscape of seismic hazards, urban growth and stretches of hot, dry days.