SUNOL, CALIF. — Representatives from the San Francisco Public Utilities Commission (SFPUC), together with local and state officials, broke ground on construction to replace the existing Calaveras Dam in unincorporated Alameda County. With a signal from SFPUC General Manager Ed Harrington, a large bulldozer cut the first large notch in the existing dam since it was originally built in 1925.

The Calaveras Dam is part of the Hetch Hetchy Regional Water System that provides drinking water to 2.5 million people in Alameda, Santa Clara, San Mateo, and San Francisco counties. Since 2001, after Calaveras Dam was deemed seismically unsafe by the California Division of Safety of Dams, water levels in the reservoir have remained at 40 percent of full capacity. The Calaveras Dam Replacement Project will allow the water levels back to the historic capacity of 31 billion gallons.

The Calaveras Dam Replacement Project will replace the existing dam with a 220-foot-high, new seismically designed earth and rock-fill dam that will be constructed right next to the existing one. The existing dam will be left in place and fully submerged underwater when the project is complete. Approximately 7 million cubic yards of material will be excavated to construct the new dam.

“The amount of material that will be excavated to build the new dam is the equivalent of two Great Pyramids of Giza,” said Harrington. “That is the size and scale of the projects we are constructing to improve the seismic and water reliability of the Hetch Hetchy water system.”

The ceremony highlighted the key features of the project including: a new spillway that will be 1,550 feet long utilizing 40,000 cubic yards of concrete, the installation of fish passage screens and a fish ladder at the Alameda Creek Diversion Dam to support the restoration of Steelhead to the Alameda Creek Watershed, construction of a new intake/outlet tower consisting of a 20-foot-diameter by 163-foot-deep vertical shaft and three new tunnels to convey water to and from the reservoir.

The contract for construction was awarded to Dragados USA Inc./Flatiron West Inc./Sukut Construction Inc. Joint Venture. Major construction is anticipated to be complete in 2015.

The $416 million Calaveras Replacement Dam Project is part of the SFPUC’s $4.6 billion Water System Improvement Program (WSIP) to repair, replace, and seismically upgrade the aging pipelines, tunnels, and reservoirs in the Hetch Hetchy Regional Water System. The Calaveras Dam Replacement Project is the 71st of the total 81 projects in the WSIP to begin construction. The WSIP is approximately 50 percent complete.

“More than 2.5 million people in the Bay Area rely on the Hetch Hetchy Water System,” said Harrington. “Each project improves our ability to continue delivering water after a major seismic event or during a sustained drought.”