COMMITTEE AGENDA MEMORANDUM
Environmental and Water Resources Committee
Government Code § 84308 Applies: Yes ☐ No ☒
(If “YES” Complete Attachment A - Gov. Code § 84308)
SUBJECT: title
Receive an Update on the Desalination Engineering Feasibility Study.
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RECOMMENDATION: Recommendation
Receive an Update on the Desalination Engineering Feasibility Study.
Body
SUMMARY:
This memorandum provides an update on the Desalination Engineering Feasibility Study. Since the last update to the Environmental and Water Resources Committee (EWRC) on April 2, 2025, Valley Water has completed the Fatal Flaw Analysis, initiated the alternatives analysis, conducted additional regulatory and environmental partner coordination, and begun refining feasible alternatives for further evaluation.
BACKGROUND
Valley Water continues to assess desalination as a potential future water supply source and in 2023, completed the Desalination Environmental Feasibility and Planning Study (DEFPS), which identified intake options, facility locations, and brine management strategies. These elements form the foundation for the ongoing engineering-level evaluations.
ENGINEERING FEASIBILITY STUDY
The Engineering Feasibility Study has two components, the Fatal Flaw Analysis and Alternatives Analysis:
1. Fatal Flaw Analysis: The Fatal Flaw Analysis screened potential desalination alternatives identified in the DEFPS, along with options newly proposed by Valley Water. Alternatives that were unlikely to receive environmental or regulatory approval, were technically infeasible, or did not meet the 10-40 million gallons per day (MGD) production target were removed from further consideration.
2. Alternatives Analysis: The Alternatives Analysis evaluated those options passing through the Fatal Flaw Analysis and further refined them to determine engineering feasibility. These include the following components:
Intake Locations
Intake alternatives are based on applicable guidance from the California Water Code, San Francisco Basin Plan, and relevant sections of the California Ocean Plan (COP). Intake locations under evaluation include:
• Deep South San Francisco Bay
• Mouth of Coyote Creek
• Northern portion of Guadalupe Slough
Potential intake structures include on-bank/near-shore intakes and offshore submerged intakes using passive screen technologies.
Facility Siting
Potential facility locations were evaluated based on physical benefits and regulatory, technical, geotechnical, and land-use considerations. The three remaining siting options are:
• Sunnyvale Baylands
• Palo Alto (former Los Altos Treatment Plant site)
• San Jose near the Silicon Valley Advanced Water Purification Facility
Brine Management
Potential brine discharge alternatives include:
• Commingling with effluent from the San Jose wastewater treatment facility
• Use of a deep-water South Bay outfall
REGULATORY COORDINATION AND OUTREACH
Given the significant permitting requirements for intake structures, facility siting, and brine management, Valley Water has continued to coordinate closely with regulatory agencies and environmental partners. Since the last update, staff has met with the Regional Water Quality Control Board (Regional Board), the State Water Resources Control Board (State Board), and environmental organizations to inform them of the Study progress.
At a meeting on October 3, 2025, regulators agreed with Valley Water’s conclusion that the California Ocean Plan does not apply to the South Bay. State Board staff will review our technical findings and potentially issue a concurrence letter. This determination, combined with hydrogeologic conditions showing disconnected aquifers and widespread impermeable Bay mud, supports the continued evaluation of surface intake options over subsurface intakes.
Valley Water also engaged with the Bay Conservation and Development Commission (BCDC), Mid-Peninsula Open Space District, and the Citizens Committee to Complete the Refuge (CCCR). Staff additionally presented updates to the Recycled Water Committee to maintain stakeholder awareness and input.
NEXT STEPS
Staff will continue engagement with regulatory agencies and environmental partners while completing the detailed alternatives analysis. Additional updates will be provided at the 50% and 100% milestones of the Alternatives Analysis Report. A final update on the Desalination Engineering Feasibility Study will be presented to the Board of Directors upon Study completion in spring 2026.
ENVIRONMENTAL JUSTICE IMPACT:
There is no environmental justice impact associated with this item. This action is unlikely to or will not result in adverse impacts.
ATTACHMENTS:
Attachment 1: PowerPoint
UNCLASSIFIED MANAGER:
Manager
Kirsten Struve, 408-630-3138