The replacement dam at Calaveras Reservoir has reached its full height, marking a major milestone in the Calaveras Dam Replacement Project in California.
According to the San Francisco Public Utilities Commission, California Department of Water Resources Division of Safety of Dams and Bay Area Water Supply and Conservation Agency, the earth and rock fill dam has been built to its full height of 220 feet, concluding the dam construction portion of the project.
SFPUC will begin refilling the reservoir this winter. To complete the overall project, crews still need to construct access roads, automate instrumentation and controls, restore the site, and place rock slope protection. This work is slated to happen in the spring of 2019.
The new dam was built because of seismic concerns about the existing 93-year-old Calaveras Dam. Calaveras Reservoir is the largest of the SFPUC’s five Bay Area reservoirs, capable of storing 31 billion gallons of water at full capacity. Since 2001, levels behind the dam have been reduced to 40% because of these concerns.
“We know that it is only a matter of time until we experience another major earthquake, and our critical infrastructure needs to be ready,” said London N. Breed, mayor of San Francisco. “This important improvement project at the Calaveras Reservoir will make sure that our water systems are seismically resilient and our local water supply is secure when the next big one strikes.”
The new dam is composed of seven zones of different materials, with the majority of the earth, rock, sand and clay used for the structure being sourced from onsite. The new dam took two years to construct and is located directly adjacent to the old dam. It has been built to withstand a 7.25 magnitude earthquake on the nearby Calaveras Fault.
The Calaveras Dam Replacement Project cost $823 million and is the largest project of the $4.8 billion Water System Improvement Program to repair, replace and seismically upgrade key components of the Hetch Hetchy Regional Water System. The SFPUC, together with its 26 wholesale customers, launched this program in 2002, and it is now more than 96% complete.