Pacheco Reservoir Expansion

A collaboration between Valley Water, the San Benito County Water District, and the Pacheco Pass Water District, the Pacheco Reservoir Expansion Project is a strategic and long-term investment toward ensuring a more reliable supply of safe, clean drinking water in the face of climate change.

The project will boost Pacheco Reservoir’s operational capacity from 5,500 acre-feet to up to 140,000 acre-feet, enough to supply up to 1.4 million residents with water for one year in an emergency. The project will also reduce the frequency and severity of water shortages during droughts, protect our drinking water supply and infrastructure, and improve fish habitat.

In February 2021, Valley Water held two virtual public scoping meetings and detailed five dam alternatives being evaluated for the Pacheco Reservoir Expansion Project as part of the California Environmental Quality Act process. Valley Water is also evaluating an option of no expansion. Click on the photos tab at the right to view the images.

Virtual public information meeting

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Join us Thursday, Feb. 13 from 5 to 7 p.m. to learn more information about the draft Environmental Impact Report on the Pacheco Reservoir Expansion Project.
Join us on Thursday, Feb. 13 from 5 to 7 p.m.
Virtual Public Meeting via Zoom
https://valleywater.zoom.us/j/85762031311
Dial-in +1 669 900 9128
Webinar ID: 857 6203 1311
Valley Water releases Draft Environmental Impact Report on the proposed Pacheco Reservoir Expansion Project

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Valley Water has released a Draft Environmental Impact Report (EIR) on the Pacheco Reservoir Expansion Project for public review beginning on Wednesday, Nov. 17, 2021, and ending on Friday, Jan. 21, 2022.
The Draft EIR may be reviewed by clicking here or visiting the project page at valleywater.org/project-updates/a1-pacheco-reservoir-expansion-project.
Valley Water will also be hosting a virtual public meeting on Jan. 13, 2022, from 5 to 7 p.m. to answer questions about the Draft EIR. The meeting will include a detailed presentation of the Draft EIR.
To join the webinar, please save the link below. The meeting information is also available on the Valley Water website.
https://valleywater.zoom.us/j/85762031311
Dial-in +1 669 900 9128
Webinar ID: 857 6203 1311
Valley Water Board of Directors unanimously approves funding commitment for Pacheco Reservoir Expansion Project to remain eligible for state funding

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On Nov. 9, 2021, the Valley Water Board of Directors unanimously approved a funding commitment for the Pacheco Reservoir Expansion Project to remain eligible for up to $496 million in conditional funding from the state’s Prop 1 Water Storage Investment Program (WSIP).
The WSIP funding represents a significant portion of the Pacheco project’s estimated $2.5 billion cost. Valley Water is exploring various dam alternatives that could reduce the cost to $2 billion.
To remain eligible for WSIP funding, the Valley Water Board of Directors was required to commit at least 75% of the non-state funded cost-share. Valley Water will cover this funding commitment through water utility revenues, the Safe, Clean Water and Natural Flood Protection Program Revenues, other Valley Water funds, and Pacheco Project partners.
As part of the WSIP requirement, Valley Water must also complete feasibility studies and make draft environmental documents for the Pacheco Reservoir Expansion Project available for public review.
Valley Water is preparing to publish the draft Environmental Impact Report (EIR) for public review on Nov. 17, 2021. The document will be accessible on the Valley Water website at valleywater.org/project-updates/a1-pacheco-reservoir-expansion-project and in person at various libraries in Santa Clara, San Benito and Merced Counties. Check our project page on Nov. 17 for a list of locations.
Valley Water will hold a public meeting on Jan. 13, 2022, from 5-7 p.m. to present the draft EIR and answer questions.
The Valley Water Board of Directors will consider approval of the Pacheco Reservoir Expansion Project following completion of the Final Environmental Impact Report.
In February 2021, Valley Water held two virtual public scoping meetings and detailed five dam alternatives being evaluated for the Pacheco Reservoir Expansion Project as part of the California Environmental Quality Act process. Valley Water is also evaluating an option of no expansion.
We are actively looking at ways to bring down the costs to ratepayers. Beyond the $496 million in state money, we are looking at federal grants and the Biden administration’s infrastructure package. Valley Water is also applying for Water Infrastructure Finance and Innovation Act (WIFIA) funding, a low-cost federal loan that is typically cheaper than what Valley Water can borrow on its own, bringing down the loan costs needed to fund the project.
Valley Water evaluating five dam alternatives for the proposed expansion of Pacheco Reservoir

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In the face of climate change and severe weather, there is a risk of more prolonged droughts in California. Despite recent storms in March, Santa Clara County is now in a drought and it is unknown how severe it will get.
Valley Water remains focused on preparing for future dry and wet years through a variety of projects and programs, including the proposed expansion of Pacheco Reservoir in southern Santa Clara County. The project would increase the reservoir’s capacity from 5,500 acre-feet to up to 140,000 acre-feet, enough water to supply up to 1.4 million residents for one year.
The project is a collaboration between Valley Water, the Pacheco Pass Water District and the San Benito County Water District. Pacheco Reservoir is located 60 miles southeast of San Jose and sits to the north of Highway 152. The existing dam is about 100 feet high and is owned and operated by the Pacheco Pass Water District.
In February 2021, Valley Water held two virtual public scoping meetings and detailed five dam alternatives being evaluated for the Pacheco Reservoir Expansion Project as part of the California Environmental Quality Act process. Valley Water is also evaluating an option of no expansion.
Variations of the alternatives include two different locations, two dam types and two reservoir sizes. The cost estimates for the alternatives range from $2.1 billion to $2.5 billion.
The two locations are described as the upstream site and downstream site. The upstream site, located about 1.7 miles from Highway 152, would allow for a greater amount of channel restoration between the new dam and the existing dam. This would create new habitat for the threatened South-Central California Coast Steelhead population and other species.
The downstream site is located about one mile from Highway 152 and is closer to the existing dam.
The reservoir sizes being considered include a 140,000-acre foot reservoir located at both sites, and a 96,000-acre-foot dam located at the upstream site.
Two different dam types being considered include a hardfill and earth filled dam, which are both designed to withstand a large earthquake.
A hardfill dam is a newer technology that uses rock materials mixed with cement and compacted together. The strength of this material allows for steeper slopes on the dam faces and a smaller footprint. The spillway and inlet/outlet pipelines can be built into the hardfill dam structure, allowing reservoir overflows to spill over the body of the dam through a channel.
An earth fill dam is similar to Valley Water’s existing dams and would require a separate spillway and inlet/outlet pipelines.
All dam alternatives include:
- A new dam and expanded reservoir upstream of the existing dam.
- A connection to the existing Pacheco conduit that will allow for water from San Luis Reservoir to be pumped and stored in the existing Pacheco Reservoir. Pacheco Reservoir is also located about eight miles west of San Luis Reservoir, which is jointly owned and operated by the U.S. Dept. of Reclamation and the California Dept. of Water Resources.
- The removal of the existing dam and restoring the channel between the old and new dams.
- Making roadway improvements from Highway 152 to the dam site.
- Building new powerlines.
- Activities related to construction of the dam.
Video recordings of the virtual scoping meetings held in February can be viewed at www.valleywater.org/pachecoexpansion.