San Francisco — The San Francisco Public Utilities Commission (SFPUC), the California Department of Water Resources Division of Safety of Dams and the Bay Area Water Supply and Conservation Agency (BAWSCA) announced that the replacement dam at Calaveras Reservoir has reached its full height, marking a major milestone in the Calaveras Dam Replacement Project.
“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 Mayor London N. Breed. “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.”
With the earth and rock fill dam now built to its full height of 220 feet, the dam construction portion of the project is finished. Crews still need to construct access roads, automate instrumentation and controls, restore the site, and place rock slope protection before the construction of the overall project is complete, which is slated to happen in spring of next year.
Since 2001, reservoir levels behind the 93-year-old Calaveras Dam have been reduced to 40 percent of capacity due to seismic concerns. Calaveras Reservoir, located on the border between Santa Clara and Alameda counties, is the largest of the SFPUC’s five Bay Area reservoirs, capable of storing 31 billion gallons of water at full capacity. With the dam now at full height, the SFPUC will begin refilling the reservoir this winter.
While the Hetch Hetchy Reservoir in the Sierra Nevada Mountains supplies 85 percent of the drinking water to the SFPUC’s 2.7 million customers, the remaining 15 percent is delivered through the SFPUC’s five water supply reservoirs in the Bay Area. Restoring the Calaveras Reservoir to full capacity is key to ensuring a reliable water supply for SFPUC customers in four Bay Area counties.
“Customers across the Bay Area depend on us for clean, safe and reliable drinking water and we take that responsibility seriously,” said Harlan L. Kelly, Jr. “The Calaveras Reservoir is a critical resource for our local water supply and a major example of how we work every day to plan for our system’s future. It is the largest of our five reservoirs and with it at full capacity, we will maximize water reliability for our customers. Hetch Hetchy Reservoir is the backbone of our water system, but it is nearly 200 miles away. With our local reservoirs at full capacity, we will be able to completely deliver our services, even in the unfortunate scenario where we cannot access the Hetch Hetchy Reservoir.”
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. Constructed like a seven-layer cake turned on its side, the dam took two years to construct. The new dam is located directly adjacent to the old dam and has been built to withstand a 7.25 magnitude earthquake on the nearby Calaveras Fault. Earlier this month, a 3.4 magnitude temblor shook the area, and no damage occurred to the new dam or its accompanying structures.
Under the State of California Department of Water Resources, the Division of Safety of Dams (DSOD) provides oversight to the design, construction, and maintenance to nearly 1,250 dams in California, including the Calaveras Dam.
“Given California’s complex geology and tectonic regime, many of the dams in California, such as the Calaveras Dam, are located near major faults and can be subject to severe loading conditions,” said DSOD Division Chief Sharon K. Tapia. Ensuring the seismic stability of the dams in California is paramount for public safety. As one of California’s largest seismic retrofit projects, the Calaveras Dam Replacement Project is a model project in its robust design features and construction standards.”
The Calaveras Dam Replacement Project is the largest project of the $4.8 billion Water System Improvement Program (WSIP) to repair, replace, and seismically upgrade key components of the Hetch Hetchy Regional Water System. The SFPUC, together with its 26 wholesale customers, launched the WSIP in 2002. One of the largest water infrastructure projects in the country, the WSIP is now more than 96 percent complete.
“Completion of this huge new reservoir is very good news for the 1.8 million residents, 40,000 businesses including those in Silicon Valley, and thousands of community agencies in Alameda, San Mateo, and Santa Clara counties, who will receive reliable, high-quality water from it,” said Nicole M. Sandkulla Chief Executive Officer/General Manager of BAWSCA. “Calaveras will provide major new water-supply protection for these vitally important customers, whose interests BAWSCA represents under state law, AB 2058. I want to congratulate the highly skilled men and women and their union representatives, who built this magnificent dam. And I applaud the leaders of the San Francisco Public Utilities Commission, who designed and will operate it.”
Crews working on the Calaveras Dam Replacement Project moved about 12 million cubic yards of earth and rock to construct the new dam. Of that total, roughly four million cubic yards of material was used for the new dam, while the remainder was placed in other areas on site. The Project has moved enough rock and soil to fill Levi’s Stadium from top to bottom four times.
Construction on the Calaveras Dam Replacement Project began in 2011. It is scheduled to conclude in spring 2019. To date, more than 1,400 workers have contributed 1.4 million total craft hours to construct this project. The total cost of the project is $823 million. Funding for the project came from a bond measure that was approved by San Francisco voters in November 2002 and paid for by both retail customers in San Francisco and 26 wholesale customers that serve Alameda, San Mateo and Santa Clara counties.