Calaveras dam finally complete, seismically retrofitted

The new Calaveras dam, on the border of Alameda and Santa Clara counties, is finally complete.

The San Francisco Public Utilities Commission built the new dam to replace the existing Calaveras dam, because it was seismically unsafe. The SFPUC is the owner and operator of the Hetch Hetchy Regional Water System.

“This is really a key component water supply for the 2.7 million customers that we serve in the Bay Area, which is San Francisco, San Mateo County, northern Santa Clara and even up to Alameda,” Steven Ritchie, Assistant General Manager of the Water Enterprise, of the SFPUC.

The old Calaveras dam was built in 1925. In 2001, state dam officials inspected it and feared a collapse, which gave way to the Calaveras Dam Replacement Project. The SFPUC had to reduce the water levels by two thirds when construction crews broke ground in 2011.

“This is the largest local reservoir that gets blended with Hetch Hetchy water to deliver to customers every year, every day,” Nicole Sandkulla, CEO of the Bay Area Water Supply and Conservation Agency, said.

Ritchie said the dam is 16 years in making. It took seven years of construction due to unexpected delays. Crews found two ancient landslides in unstable material meaning they had to move a lot more dirt than originally expected. Thousands of fossils from 15 to 20 million years ago were carefully removed. 

The project came in at double the original budget at more than $820 million, but officials said if there is ever an earthquake, the dam is expected to withstand the big one.

“It’s actually designed for a 7.25 earthquake which is very large and that’s on the Calaveras fault,” Sharon Tapia, Division Chief for the California Division of Safety of Dams, said. “Seismic safety is a concern for the dams in California and we been working for decades to evaluate them.”

Sandkulla said if there is ever a disruption to the Hetch Hetchy supply, their agencies will be fully relying on the water from the Calaveras Reservoir.

“Now that it's fixed, the rains hopefully are going to come. It will get filled up this year. It will be a great year for a banner water year. We'll have a lot more reliability,” Sandkulla said.

The dam was built with a bigger base and a bigger top. It will allow the SFPUC to raise the dam many more feet and store more water due in there is ever a need to survive through a drought. When full, it will hold roughly 30 billion gallons of water.