Tunnel Beneath the Bay
FOR DECADES, CALIFORNIA'S HETCH HETCHY WATER SYSTEM HAS SUPPLIED WATER TO THE SAN FRANCISCO BAY AREA. BUT THE AGING SYSTEM IS NEARING THE END OF ITS USEFUL LIFE AND IS SEISMICALLY VULNERABLE.
Stretching from the Sierra Nevada Mountains across central California to the San Francisco Bay, the Hetch Hetchy water system is one of the largest water collection systems in the U.S. The system collects water from the Tuolomne River watershed in the Sierra Nevada and stores it in three reservoirs in Yosemite National Park. From there, a series of tunnels and pipelines carry the water 150 miles west to consumers in the Central Valley and in the San Francisco region. Handling more than 220 million gallons of water every day, the system serves more than 2.4 million residents and businesses. In addition to supplying 85 percent of San Francisco’s water demand, the Hetch Hetchy system generates roughly 1.7 billion kilowatt-hours of electric power every year.