Representatives from SFPUC, together with local and state officials, broke ground on construction to replace the existing Calaveras Dam in unincorporated Alameda County on Friday.

The Calaveras Dam – originally built in 1925 – 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% of full capacity. The Calaveras Dam Replacement Project will allow the water levels back to the historic capacity of 31 billion gallons.

The replacement project will replace the existing dam with a 220ft 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 ground-breaking ceremony highlighted the key features of the project including: a new spillway that will be 1550ft-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 20ft-diameter by 163ft-deep vertical shaft and three new tunnels to convey water to and from the reservoir.

The contract for construction was awarded to a JV of Dragados USA, Flatiron West and Sukut Construction. Major construction is anticipated to be complete in 2015.

The Calaveras Dam Replacement Project is the 71st of the total 81 projects in the WSIP to begin construction. The WSIP is approximately 50% complete.