Proposed $1B dam takes step forward
Construction on reservoir near Pacheco Pass would start in 2024
A plan to build a huge $1.1 billion dam and reservoir near Pacheco Pass in southeastern Santa Clara County is taking a significant step forward with the release of hundreds of pages of environmental studies.
The project, which would be the first new large dam built anywhere in the Bay Area since Los Vaqueros Reservoir in Contra Costa County in 1998, grew out of California’s recent five-year drought.
Environmentalists have raised concerns about the project’s costs, and the fact that it would submerge 1,245 acres of oak woodlands on the north side of Highway 152 near Casa de Fruta — an area equal to about 943 football fields.
But the Santa Clara Valley Water District, a San Jose government agency that provides water to 1.9 million Silicon Valley residents, says the reservoir is needed to store more water as insurance against California’s next drought.
“It will improve our water supply reliability,” said Linda LeZotte, chairwoman of the water district, which is proposing the project. “One of the things I heard most from people during the drought was ‘Why don’t you have more storage capacity?’ ”
Two weeks ago, the U.S. Bureau of Reclamation released a 327-page draft environmental impact study that includes details of the Pacheco project. The agency, along with the water district, has scheduled a public meeting to discuss the project and the environmental study at 6 p.m. Monday at the Gilroy Library, 350 W. Sixth St.
The water district hopes to begin construction in 2024. It would take 475 construction workers five years to complete the project working 24 hours, 7 days a week, according to the new environmental study.
Under the proposal, the wa
ter district would replace a small, existing dam and reservoir on the site.
The existing reservoir was built on the North Fork of Pacheco Creek in 1939 behind a 100-foot earthen dam now badly in need of costly repairs. It holds only 5,500 acre-feet of water, while the new reservoir would hold more than 23 times as much — 140,000 acre-feet. By comparison, the largest reservoir in Santa Clara County, Anderson Reservoir, has a maximum capacity of 90,000 acre-feet. An acre-foot is 325,851 gallons, or an acre of land a foot deep in water, roughly the amount that an average California family of five uses in a year.
The new dam would be 319 feet tall. The district would take water it now stores in nearby San Luis Reservoir and pipe it into the new reservoir, filling it during wet years.
District officials say that the project also would have environmental benefits. It would provide a more regular supply of water downstream for endangered steelhead trout, they note. And, they say, it would offer better flood protection
to people living along Pacheco Creek and the Pajaro River.
It also would allow the agency to store more water in wet years to reduce shortage in dry years. Specifically, district officials say, the project would help fix a long-running problem at nearby San Luis Reservoir, the massive inland sea in Merced County where the Santa Clara Valley Water District stores some water that comes from the Delta.
The problem is that in dry years, when the San Luis Reservoir falls below about 15% full, the reservoir’s water warms. That
causes algae blooms, which make the water more expensive to treat, and give it an unpleasant taste. If the reservoir level falls low enough, the water can drop below intake pipes and the water district has no way of getting it out.
Working to fix that problem, the Bureau of Reclamation on July 25 released an environmental study looking at several options. Among them: raising the height of the dam at San Luis, building lower intake pipes, changing the way the district filters and treats its water, and building the new Pacheco Reservoir.
The bureau chose the Pacheco Reservoir as the preferred alternative. Public comments on the study will be taken through Sept. 24, and a final environmental report is expected out by next summer.
The water district received a huge boost last year when the administration of former Gov. Jerry Brown awarded it $485 million from Proposition 1, a $7.5 billion water bond passed by voters in 2014 during the depths of the state’s recent five-year drought.
But the Pacheco project still has many hurdles before construction can begin.
The Santa Clara Valley Water District has to find at least $600 million more to pay for it. The agency is hoping that will come from the federal government and other Bay Area water districts that could work as partners and share the water.
Second, although the small existing reservoir is owned by the Pacheco Pass Water District, a tiny agency working with the Santa Clara Valley Water District, most of the ranch land surrounding the site was purchased in late 2017 by a wealthy businessman who swept in and beat the water district to the property.
That buyer, Edmund Jin of Atherton, founded JLA Home, a successful importexport business for home furnishings. Jin has limited access to the property to the water district, which has sued him over the issue. Eventually, the district could use eminent domain to take thousands of acres from Jin, but that could result in a costly legal battle.
Finally, environmental groups have concerns. And that could lead to lawsuits. The Sierra Club’s local Loma Prieta chapter says the project is too expensive and that future supply could instead be better and more cheaply secured with more conservation, water recycling, stormwater capture and by raising the height of Los Vaqueros Reservoir.
“The environmental impacts are going to be really large in that area,” said Katja Irvin, conservation chair of the Sierra Club Loma Prieta chapter. “It’s a pretty pristine natural area. The dam is going to inundate all this prime oak forest and stream habitat. They are going to build a cement plant and quarry there. And the truck traffic there is going to be insane on Pacheco Pass.”
She added: “It’s a lot of money. It could be spent more efficiently and in ways that are less damaging to the environment.”
LeZotte, the water district chairwoman, said the agency is already expanding many of those other options.
“I always have an open mind to what the environmental community speaks about,” she said. “But this expands the reservoir to 140,000 acre-feet. That’s a lot of water. You can’t get that just through conservation and recycling.”
To read the new environmental study, go to www. valleywater.org/project-updates/public-review-documents.