Sierra Club and Amah Mutsun Tribal Band Join Growing Coalition Challenging Valley Water’s Proposed Pacheco Dam Project

Proposed Pacheco Dam Impact Area (Graphic: Business Wire)

SAN JOSE, Calif.--()--The Stop Pacheco Dam Coalition, which filed a lawsuit against Santa Clara Valley Water District’s (Valley Water) Pacheco Dam project in June, has been joined by the Sierra Club and the Amah Mutsun Tribal Band. The lawsuit challenges Valley Water’s reliance on exemptions from the California Environmental Quality Act (CEQA) for the extensive geotechnical and other investigations to plan and engineer the proposed 140,000-acre foot reservoir project atop remote Pacheco Pass in southern Santa Clara County.

The challenged investigations include over 200 drilling sites (accessed with trucks, tractors and helicopters) and digging more than 50 test pits in the Diablo Range, an area rich in biodiversity and cultural resources. The Coalition’s lawsuit asserts that CEQA requires Valley Water to prepare an environmental impact report to analyze and mitigate the many significant environmental impacts associated with the geotechnical and other exploration activities at the proposed Dam site.

In addition, the Sierra Club, a national non-profit organization of nearly one million members, is formally supporting the Stop Pacheco Dam Coalition as concerns escalate about the negative environmental impacts that would result from both the investigation activities as well as the eventual construction of this controversial dam project.

“The Sierra Club is dedicated to the responsible use of the earth’s resources. Valley water should not get a free pass to dig up this irreplaceable landscape, especially without proper environmental review and mitigation,” said Katja Irvin. “The extraordinary cost of the project would significantly increase water charges, which many Santa Clara County residents can’t afford. Valley Water should be pursuing lower cost alternatives with fewer environmental impacts to provide needed water supplies.”

The diverse and growing group of entities opposing the investigations in furtherance of the Pacheco Dam also now includes the Amah Mutsun Tribal Band.

“The Amah Mutsun are working with the Coalition to prevent the irreparable destructive impacts of the dam project, including the investigation efforts, which would disturb sacred and ceremonial sites,” said Valentin Lopez, chairman of the Amah Mutsun Tribal Band and Land Trust. “This area includes burial sites, ceremonial sites, and other culturally important sites, some of which are over 3,000 years old.”

The lawsuit condemns Valley Water for skirting the required environmental review of the proposed Pacheco Dam. The Coalition, which includes Friends of the River and the Pacheco Land and Cattle Co., filed the initial lawsuit in June 2022, and are working to protect the unique biological, cultural and other resources of this part of the Diablo Range, as well as statewide taxpayers and Santa Clara County ratepayers. According to the Coalition, the new Pacheco Dam would pose too great a risk financially, without solving Silicon Valley’s water challenges.

“We are happy to be joined by additional partners working to ensure that the environmental impacts of the pre-dam exploratory work are fully analyzed and mitigated,” said Coalition attorney, Osha Meserve. “This dam project is infeasible, irresponsible, and poses far too much environmental harm to be justified. Valley Water has not been forthcoming regarding costs, environmental impacts or expected water supplies from damming the usually tiny Pacheco Creek. We look forward to our diverse group working together to advocate for environmental protection of this still wild area of Santa Clara County as well as transparency for ratepayers.”

You can read more about the growing problems with this controversial dam project, which the Coalition details in a recent letter to the California Water Commission. To view the amended lawsuit, click here.

About our Coalition

Our Coalition aims to protect Santa Clara County’s ratepayers and the environment, as well as working ranchlands, from this wasteful and high-risk project. For more information, visit our website at


Stop the Pacheco Dam Project


Social Media Profiles


Stop the Pacheco Dam Project