County Water Resources Agency details subgrant projects for Salinas Valley groundwater sustainability; ASR not viable alone
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Summary
County Water Resources Agency staff told supervisors Oct. 28 that state subgrant funding has advanced planning and feasibility work for Castroville seawater intrusion reductions, canal alternatives tied to historic water rights and expanded groundwater monitoring, but an ASR option relying only on existing water rights was judged not viable.
The Monterey County Water Resources Agency (WRA) briefed the Board Oct. 28 on subgrant work being carried out in partnership with local Groundwater Sustainability Agencies (GSAs) under Department of Water Resources funding. Shauna Murray summarized activities funded by two DWR subgrant agreements (one beginning Sept. 2022, the other Jan. 2025) totaling roughly $3.7 million to the agency for planning, feasibility and staff support.
Murray described three buckets of work: (1) studies and capital improvements to optimize existing in‑lieu supply facilities such as the Castroville Seawater Intrusion Project (CSIP); (2) new project studies including investigation of irrigation‑in‑lieu alternatives and re‑use of regional wastewater; and (3) data collection, monitoring and a groundwater monitoring program. The grants were used to develop concept designs and feasibility analyses for several CSIP capital improvements, including pipe and pressure improvements and an estimated 10–12 million gallon in‑system storage option, with rough order‑of‑magnitude cost estimates in the tens of millions.
An aquifer storage and recovery (ASR) study for the 18400 aquifer concluded that existing local supplies would not support a stand‑alone ASR project without additional surface water or a new water right. Murray said the ASR concept yielded useful lessons but was not viable as a standalone retrofit using only current facilities and rights.
Another project described was the Castroville and Eastside Canals & Alternatives study, which is exploring potential use of County water right permit 11043 (a historic right) for diversion in some years. The phase‑1 work analyzed historical diversion records and estimated potential diversions substantially below the permit maximum; phase 2 will examine alternatives and costs with anticipated results next spring. Monitoring and data work has been expanded under grant funding, including well registration, extraction reporting and plans for additional monitoring of deeper aquifers.
The WRA will continue to work with GSAs to evaluate what project and management actions meet sustainable groundwater objectives and to frame potential funding and partnership options; the GSA is expected to consider strategies and a workplan in spring and make decisions on fall 2026 timing for further actions.
Why it matters: These state subgrants support regional groundwater sustainability planning and exploration of supply alternatives that could reduce pressure on groundwater and mitigate seawater intrusion in parts of the Salinas Valley, but they have not yet funded final designs or construction — and some concepts (like ASR relying only on existing rights) were judged unworkable without additional supplies or rights.
Provenance: WRA subgrant update, Oct. 28, 2025 (presentation by Shauna Murray) (topicintro: 7081.37–7101.66; topfinish: 7685.58–7702.39).
