Following regulatory guidance from the State Division of Safety and Dams (DSOD), Valley Water plans to upgrade the Almaden Dam in South San Jose. The Almaden Dam Improvement Project will ensure the dam’s operational safety and ability to deliver water to Santa Clara County residents. The project will make improvements to key dam components in addition to environmental benefits.








Almaden Dam Background
Almaden Dam was constructed in 1936 to provide operational stability for the Almaden Reservoir, which had been built the previous year. The 110-foot earth-filled dam has a 500-foot crest, and its primary function is to hold water in the reservoir for Santa Clara County’s local water supply, incidental flood management, and groundwater recharge. Approximately 8% of our local water supply comes from the Almaden Reservoir
Project Objectives
Valley Water is evaluating recommended alternatives to address sediment accumulation at the intake structure, insufficient spillway capacity, and updating the outlet structure. The recommended alternatives include:
- System Upgrades:
- Replace outlet works with new intake structure (delivers reservoir water to the outlet structure)
- Modify the outlet structure (releases water from the reservoir), piping, and valves.
- Spillway Improvements: Constructing a new spillway to current design standards.
Project Update and Timeline
This project is currently in the final stages of the planning phase and will begin the design phase in early 2025. Environmental documentation preparation is ongoing and expected to be completed by 2029 when a public meeting will be held to obtain comments on the Draft Environmental Impact Report.
January Public Meeting
The presentation from the January 23 public meeting is available to download, and a recording is available for viewing.
Project Background and Timeline
- 2000: Valley Water launched the Almaden Dam Improvement Project to address mercury-contaminated sediment accumulation at the dam's intake structure and correct the infrastructure of the aging outlet works.
- 2005: A seismic stability evaluation for the dam halted during the planning phase.
- 2011-2012: The seismic stability evaluation found the dam and embankment seismically stable. However, the intake tower and spillway capacity still require work to ensure long-term reliability.
- 2016: Valley Water's Board of Directors approved the performance of improvements to the Almaden-Calero Canal and the improvements at the Almaden Dam. Project improvements were placed on hold to address the work needed on the Anderson, Calero, and Guadalupe dams.
- 2023-2024: The DSOD evaluates the Almaden Dam and downgrades their rating from “fair” to “poor”. The project hold is removed, and the planning phase continues.
- 2025: The project will enter the design phase in the first quarter of 2025
- 2029: The Environmental Impact Report is planned for completion.
- 2030: Planned start of construction in the fall.
- 2032: Planned completion of construction.