When built nearly a century ago, the dam forming the Calaveras Reservoir was considered the world’s biggest earth-fill impoundment. But its placed on one of California’s major fault lines led regulators in 2001 to declare the dam seismically unsafe. The result: the San Francisco Bay Area’s biggest source of drinking water was ordered to be scaled back to less than 40 percent of capacity, cutting the region’s fresh water supply.
Now, those quake-related concerns have washed away. With construction managed by a Black & Veatch-led team, a new replacement dam built near that Calaveras Fault can withstand a maximum credible earthquake of 7.25-magnitude. This ability means the San Francisco Public Utilities Commission (SFPUC) again can fill the reservoir, securing the resilience, vitality and reliability of water resources for some 2.7 million customers.
“This new dam, without question, was a massive undertaking, and Bay Area water consumers will benefit from water supply reliability for decades to come,” said Chris Mueller, Black & Veatch’s project director.
San Francisco Mayor London Breed stressed the importance of the impoundment’s structural upgrade, noting that “it is only a matter of time until we experience another major earthquake, and our critical infrastructure needs to be ready.”
The dam replacement project was the centerpiece of SFPUC’s $4.8-billion, 16-year push to overhaul its 167-mile regional water delivery system. And restoring the 4-mile-long body of water to its original capacity of 31 billion gallons reaffirms its status as the biggest of five reservoirs holding the region’s water supply. It’s additionally important for water supply resilience if supplies from the region’s main source, the Hetch Hetchy Reservoir, are ever disrupted due to a natural disaster or climate or water quality events such as earthquakes, wildfires or drought.