Part 1: Rebuilding the Historic Hetch Hetchy Regional Water System
December 28, 2011Editor’s Note: In January, Trenchless Technology readers will get an exclusive look into how trenchless technology is instrumental when rebuilding a pipeline and facilities in newly developed areas that were not there when the system was originally built.
When you think of San Francisco, most people think about the Gold Rush, earthquakes, the Golden Gate Bridge and the tech boom of Silicon Valley. However, we often take for granted the people — visionaries, local leaders and engineers — who put the San Francisco Bay Area on the map.
These people spearheaded the birth of a colossal, gravity-based water system known as the Hetch Hetchy Regional Water System, described as an “engineering marvel,” that provided enough water to sustain development and flourish an innovative metropolitan area for more than 70 years.
Most of the Hetch Hetchy Water System was built in the 1920s and 1930s. However, segments of the system date back to the Civil War when the Spring Valley Water Works began construction of Pilarcitos Dam, the first of four dams it would ultimately build on the San Francisco Peninsula.
Unfortunately, this antiquated system not only needs repair, but also seismic upgrades to its pipes — some of which are the original riveted steel and are nearing the end of their useful working life. Currently, the system delivers approximately 260 million gallons of high-quality water daily to six Northern California counties. This pristine and plentiful water source originates from the Sierra Nevada snowmelt, located 167 miles east of San Francisco, crosses three active earthquake faults and ultimately finds its way to 2.5 million Bay Area customers.
In 2002, San Francisco voters agreed to raise consumer water rates, which will triple by 2016 because most felt seismically retrofitting and upgrading their water system was worth the investment. The San Francisco Public Utilities Commission (SFPUC) began work on the $4.6 billion Water System Improvement Program (WSIP) in 2003. This major capital infrastructure program consists of more than 80 unique projects. This year marks the peak of construction, as multiple contractors work to repair, replace and seismically upgrade pipelines, dams and pump stations that make up this historic water system.
San Francisco’s Search for Water
While San Francisco is surrounded by the salty waters of the Pacific Ocean and San Francisco Bay, historically the region’s natural ecosystem had limited local drinking water. In the early 19th century, San Francisco’s first settlers depended on limited surface water — including one lake, one creek and several springs or wells. In 1849, the California Gold Rush exploded, and San Francisco grew to a population of 30,000 in one year. This unprecedented growth sparked huge demands for water, and residents were forced to purchase drinking water by the barrel. At the time, water was sold by the bucket for $1 in gold. Locals grew unsatisfied with their water supply because of the high costs, compounded with its poor taste from the local creek and lake.
In the late 1880s, the Spring Valley Water Co., the successor to the Spring Valley Water Works, became the predominant water supplier to San Francisco and was funded with proceeds from the California gold and silver boom. The company hired the brilliant, young Prussian engineer, Herman Schussler. From the late 1860s through the 1880s Schussler built four dams, all of which are still in service today. The most notable of these was the landmark Lower Crystal Springs Dam. Finished in 1890, it was the largest concrete dam in the world. It is situated just 200 yards from the San Andreas earthquake fault. It is unique because of its three dimensional, concrete jigsaw puzzle-design — the prototype to Hoover Dam. It also survived the 1906 San Andreas earthquake without any damage.
In 1906, a 7.9 earthquake shook the Bay Area and broke water mains, leaving little to no water for fighting fires. After three days of devastating fires, more than 3,000 people lost their lives and hundreds of thousands were left homeless. Visionary engineers, politicians, voters and conservationists joined forces to support the development of one of the most complex, gravity-based water systems in the world.
The Birth of the Hetch Hetchy Water System
In 1913, the U.S. Senate passed the Raker Act allowing San Francisco to build the Hetch Hetchy Reservoir at the north end of Yosemite National Park, and use it as its primary water source, despite opposition from naturalists.
While the politics to authorize the regional water system were complicated, building the system was even more daunting. Construction of a major water transmission system and hydropower operations in remote territory at the turn-of-the-century was extremely challenging. This brought some of the brightest engineers to work with San Francisco City Engineer Michael Maurice O’Shaughnessy, aptly named “The Chief.” For more than 22 years, San Francisco relied on “The Chief,” and his army of talented engineers and contractors to complete this project.
The Catalyst to Rebuild the Water System
Today, the 2.5 million residents receiving water from the Hetch Hetchy Regional System frequently overlook the fact that their water traverses through three of the nation’s most active fault lines (crossing the San Andreas, Hayward and Calaveras faults) to reach their faucets.
Considering the damage from the 1989 Loma Prieta earthquake and knowing that United States Geological Survey (USGS) experts predict a major 6.7 or greater magnitude earthquake will hit the Bay Area within the next 30 years, the SFPUC knew its infrastructure could not withstand another earthquake like the 1906 event. A similar earthquake would severely damage transmission and distribution pipelines throughout the region and would potentially leave customers in the city and surrounding area without safe drinking water for 30 days or even longer.
Steps needed to be taken to upgrade the region’s water infrastructure. This included building new facilities with increased operational flexibility to provide alternate routes for water supplies when the main transmission system fails, and create interconnections with neighboring water systems to provide water supplies in an emergency. The concentrated population growth and industrial development of the 1970s, 1980s and 1090s on the San Francisco Peninsula, including the creation of Silicon Valley, added a layer of complexity to rebuilding and seismically-retrofitting a system that was originally built across farmlands and open space*.
Keeping the Momentum
To date, 74 WSIP projects have completed construction or are currently in construction for a total value of $2.6 billion.
WSIP reached the peak of construction in June 2011, and 34 percent of construction activities in the Regional Program are complete. Within the City and County of San Francisco, the Local Program completed 30 of the 35 projects with three projects remaining in construction. In the Regional Program, 20 projects are in construction and 18 have completed construction. The entire WSIP forecasted total cost is $4.593 billion, which is $7.5 million more than the 2011 approved budget. However, due to cost-savings on recent contracts, the program-wide reserve funds have increased from $161.4 million to $167.6 million.
Similar to other large capital improvement projects, the Hetch Hetchy Water System has endured similar political challenges, environmental hurdles, some public opposition and funding challenges, as they battled nearly 100 years ago. However, what has changed over time are the technological advances used by engineers and contractors to seismically strengthen and improve the reliability of the water system.
Paul Mazza served 33 years at the SFPUC as its regional water operations manager and now and now as its lead water operations representative for WSIP. Daniel Jaimes is an onsite WSIP community outreach consultant at the SFPUC.