Huge San Joaquin Valley reservoir is expanding. Much of the water is headed elsewhere | Opinion
The federal government and some 10 water districts are ponying up $1.1 billion to expand California’s largest reservoir south of the Delta.
Their plan is to raise the dam at San Luis Reservoir outside Los Banos by 10 feet – in addition to the 10-foot raise prescribed by the seismic-strengthening project currently underway – and thus increase storage at the existing 2.04 million acre-foot facility by 130,000 acre feet.
That’s enough water to supply “more than 2 million people, a million acres of farmland and 135,000 acres of Pacific Flyway Wetlands,” according to a Bureau of Reclamation media release.
What’s not being stated publicly (outside a series of negotiation sessions) is these benefits will be felt to a much greater degree in Silicon Valley than the San Joaquin Valley, where San Luis Reservoir is located.
That’s because the biggest investor – by far – among the group of water agencies willing to help pay the freight for the B.F. Sisk Dam Raise and Expansion Project is the Santa Clara Valley Water District, which primarily serves the 1.9 million residents of Santa Clara County.
“It’s Santa Clara and everyone else,” said Scott Petersen, water policy director for the San Luis & Delta-Mendota Water Authority.
The Santa Clara Valley Water District imports 55% of its water. Much of that, including both federal and state contracts, is already stored at San Luis Reservoir and arrives at treatment facilities via a 5.3-mile tunnel through Pacheco Pass.
Now they’re seeking more. Dana Jacobsen, a Santa Clara Valley Water District senior resource specialist, said his Board has “tentatively reserved” up to 60,000 acre feet of storage in the enlarged reservoir – equating to roughly 46% of the total expansion.
That 46% share is even larger than the one reserved by the federal government. It could also come with a hefty price tag in excess of $500 million.
“We get quite a bit of water in the wet years through our state and federal contracts, but we need a way to store water in the wet years for later use when it’s dry so that we can weather those dry spells,” Jacobsen said.
“Our planning process has identified a need to diversify our storage capacity, and the Sisk Dam raise has been one of those things that we have been considering.”
To fund the reservoir expansion, the federal government and partnering water agencies have agreed to a 30% to 70% split with Uncle Sam putting up 30% and the investors putting up 70%. So far, the Biden administration has allocated $150 million toward the project.
That same 30-70 split applies to water storage. The federal government is to receive 30% of the newly created storage space, mostly to satisfy water quality and environmental requirements, while the remaining 70% is divided among the partners. The Santa Clara Valley Water District accounts for 66% of the partners’ share.
While the Bay Area agency is heavily invested, the largest water district in western Fresno County remains on the fence over whether to participate.
“We haven’t ruled it out; we haven’t committed either,” said Elizabeth Jonasson, Westlands Water District’s deputy general manager of external affairs.
Petersen of the San Luis & Delta-Mendota Water Authority, which operates the Delta Mendota Canal and is the project’s co-lead agency alongside the Bureau of Reclamation, said the costs make it prohibitive for agriculture-based water districts to take part because they have no way of passing those to rate-payers.
Even one with Westlands’ vast resources, apparently.
Highway adds to costs
Why is the B.F. Sisk Dam Raise and Expansion Project so expensive? (At $1.1 billion, it’s a smidgen more than the $1 billion seismic project underway since 2022 that involves considerably more work to the 3 ½-mile long earthen dam.)
That’s because a one-mile segment of Highway 152 must be elevated to account for the new maximum water level of the expanded reservoir. The highway work alone is estimated to cost $450 million, according to Petersen, who added the project’s investors and Caltrans are currently in negotiations over how that bill gets paid. The investors are also seeking federal funding.
Those negotiations are separate from the public negotiation sessions being held between the Bureau of Reclamation and participating members of the San Luis & Delta-Mendota Water Authority. The next sessions are Sept. 20 and Oct. 1-2 in Sacramento.
While the parties have tentatively agreed to the 30-70 funding and storage split, several details about the operating agreement still must be worked out. Petersen said the negotiations could wrap up in early 2025 if no other outstanding concerns are brought to the table.
There is no “drop-dead date” to get everything finalized. However, since the reservoir expansion project is piggybacked onto the seismic project, cost efficiencies are built into the concurrent timelines. Work on the 10-foot dam raise for the federally funded seismic project is scheduled to begin in 2027.
According to modeling estimates, the expansion of San Luis Reservoir will result in an average annual yield of 35,000 acre-feet of new water. Most of that will occur in wet years.
“We think this project has a lot of potential and could provide a lot of benefit,” Jacobsen said.
Unlike other proposed California reservoir expansions, this one has received virtually no opposition from environmentalists. Sacramento-based attorney Osha Meserve, who is battling the Santa Clara Valley Water District over its proposed expansion of Pacheco Reservoir, called San Luis Reservoir the “least worst” among projects currently on the table.
Another leading environmentalist expressed doubt the project would even happen once all of the costs and benefits are calculated.
“That’s a lot of money for not a lot of water,” said Ron Stork, senior policy advocate for Friends of the River.
Too expensive for many San Joaquin Valley farmers apparently, but not for Bay Area water consumers.
