The rolling hills and ranchlands of eastern Contra Costa County are known for wineries, cattle ranches, wind turbines and growing subdivisions.
But soon they may be known for something else: The biggest new water storage project in the Bay Area in years. And now, amid the current drought, nearly every major water agency in the region wants a piece of it.
The Contra Costa Water District is moving closer to breaking ground on plans to expand Los Vaqueros Reservoir, south of Brentwood, by raising the reservoir’s earthen dam by 56 feet, to 287 feet high. That would make it the second tallest dam in the Bay Area, eclipsed only by Warm Springs Dam on Lake Sonoma near Healdsburg, which is 319 feet high.
Construction, slated to begin in late 2023 and finish by 2030, would expand Los Vaqueros from its current 160,000 acre-feet capacity to 275,000 acre-feet, enough water when full for the annual needs of 1.4 million people.
At a time when other efforts to build new dams and reservoirs in California have struggled for lack of money, ballooning costs and opposition from environmental groups, Los Vaqueros is gaining momentum.
The idea is that part of the $1 billion cost would be shared by other Bay Area water agencies, who would receive some of the water.
“It’s about water supply reliability,” said Marguerite Patil, assistant general manager of Contra Costa Water District. “It’s not a big enough project to solve everybody’s problems, but it’s a good tool to have in the tool kit.”
Recently, the project has cleared several significant hurdles.
Last month, the Contra Costa Water District and seven other agencies formed a legal partnership to oversee the design, construction and funding of the reservoir — including negotiating in the coming year how much money each agency will contribute and how much water they will secure.
That partnership, called a Joint Powers Authority, held its first public meeting Wednesday.
Environmental studies are finished. Engineering plans are expected to be reviewed in the spring by state dam safety officials for final approval.
Two weeks ago, the California Water Commission, a nine-member agency appointed by the governor, voted unanimously to confirm that the project qualifies to receive $470 million from Proposition 1, a state water bond passed by voters in 2014.
The project also has $223 million in federal funds. The rest of the funding would come from other Bay Area water agencies.
“We’re feeling great,” Patil said.
There are still challenges ahead. To raise the dam, the reservoir will have to be drained in 2027 for three years. The district says it will provide water during that time to Contra Costa County residents directly from the Sacramento-San Joaquin River Delta and from transfers and exchanges with other districts.
Los Vaqueros Reservoir is 3 miles long. It was built in 1998, paid for by the customers of the Contra Costa Water District. In 2010, the same customers approved an advisory measure to expand the reservoir from 100,000 acre-feet to 160,000 acre-feet, by raising the dam 34 feet.
That project was finished in 2012. The reservoir, now 63% full, has reduced the impact of the last two droughts on Contra Costa County residents.
Of note: The project has never been opposed by environmental groups. Part of the reason is that Los Vaqueros is an off-stream reservoir, filled from the Delta, rather than a dam on a free-flowing river.
“They reached out early on to understand our concerns,” said Jonas Minton, senior water advisor to the Planning and Conservation League, a Sacramento environmental group. “They incorporated ways to reduce environmental impacts.”
Among those were putting in state-of-the-art fish screens on Delta intake pipes to reduce harm to fish, building a 55-mile network of public trails around the reservoir, and in the new expansion, guaranteeing some water will go to Central Valley wildlife refuges.
A decade ago, plans to expand the reservoir were discussed, but the economy was struggling and Contra Costa officials couldn’t find other agencies to help foot the bill.
Now the partnership is a who’s-who of Bay Area water leaders: The Contra Costa Water District, Alameda County Water District, East Bay Municipal Utility District, Santa Clara Valley Water District, San Francisco Public Utilities Commission, and Zone 7 Water Agency in Livermore, along with the San Luis & Delta-Mendota Water Authority, and Grassland Water District in Los Banos.
To the south, the Santa Clara Valley Water District has proposed building a major new reservoir in southern Santa Clara County near Pacheco Pass. But its costs doubled to $2.5 billion this year when the site was found to have unstable geology. It has no local funding partners so far. Environmentalists and San Jose Mayor Sam Liccardo are opposed. Pacheco Reservoir is still being planned, but the district, based in San Jose, is studying other ideas also.
“Los Vaqueros has a lot of merit,” said Tony Estremera, chairman of the Santa Clara Valley Water District, which serves 2 million people. “We are looking really hard to solve our storage problems. This is one of the best options we’ve found.”
The region’s largest water agency, the San Francisco Public Utilities Commission, which runs the Hetch Hetchy system for 2.7 million people in four counties, also is at the table.
“We still have questions about how much water we can get and how much it will cost us,” said Steve Ritchie, the commission’s assistant general manager.
Ritchie said Los Vaqueros is one of 15 projects San Francisco is considering — including raising its own Calaveras Dam east of Fremont and expanding recycled water — to help reduce water shortages over the next 50 years as the population grows and the city battles state regulators and environmentalists over how much water it can take from the Tuolumne River.
“Reservoirs are really hard to build,” Ritchie said. “They are expensive. The idea of being part of a project where new storage is actually being built, having that in the future, is a fairly tempting proposition. These opportunities don’t come along very often.”
