Napa County GSA unveils proposed groundwater fee, sets July 10 deadline for owner claims

The Napa County Groundwater Sustainability Agency on a community webinar presented a proposed groundwater sustainability fee designed to fund required monitoring and implementation of the Napa Valley subbasin Groundwater Sustainability Plan. Ryan Aston, a consultant with SEI Consulting Group, said the fee study establishes maximum rates for three user classes and the GSA will finalize rates after owner claims are processed.

The fee study divides users into agricultural groundwater users (charged by planted acre), self‑supplied groundwater users (a flat per‑parcel charge) and public water systems (charged per acre‑foot). Aston said the study sets a base agricultural rate of $38.58 per planted acre plus a supplemental $60.16 per groundwater‑irrigated acre, producing a maximum of $98.74 per groundwater‑irrigated planted acre. The self‑supplied per‑parcel rate in the study is $62.58, and the maximum rate for public water systems is $129.87 per acre‑foot of groundwater extracted.

The county has tentatively pledged $500,000 to reduce the fee burden: $300,000 applied broadly to lower rates, $100,000 targeted to self‑supplied users, and $100,000 reserved for a reserve fund and fee waivers. Aston said the reserve is capped at 15% of the annual budget and any excess would be used to reduce future rates.

"The rates established by the fee study are the maximum rates that can be levied under the adopted fee — you can think of them as the ceiling," Aston said during the presentation. He emphasized that the shown rates could be lowered if the county increases its contribution or if owner claims reduce the revenue need.

Property owners have until July 10, 2026 to submit fee‑calculation claims for dry farming status, primary use of alternative water sources (more than 50% of irrigation), vine removal or planted‑acreage changes since the assessor's Jan. 1, 2026 snapshot, or errors in parcel data. The GSA plans to process updated planted‑acre data from the Napa County Assessor in early July, consider a resolution to finalize rates at the GSA board meeting on July 28, 2026 and submit charges to the county auditor by Aug. 10, 2026 if approved.

The GSA will use the county's interactive GIS map to help owners determine whether their parcel or well lies inside the Napa Valley subbasin; staff said the governing test for liability is where irrigation water from the subbasin is applied. Aston said dry‑farm verification may use maps from the California Sustainable Winegrowing Alliance or field visits by Napa County Resource Conservation District staff. He also said recycled water generally counts as an alternative source but verification will be handled case‑by‑case.

On waivers, the GSA board limited fee waivers to self‑supplied (rural residential) households with household income at or below 80% of Napa County median income, adjusted for household size. Applicants must provide their most recent tax return (adjusted gross income) to verify eligibility; waivers would be covered from the County General Fund, not by other fee payers.

In the public Q&A, attendees raised how verification will work for mixed water sources, whether irrigation records will suffice versus meters, and whether private wells will be metered. Aston said the GSA is not planning broad mandatory metering at present; SGMA authorizes certain metering requirements for non‑de minimis users but staff said mandatory metering for rural residential users is not currently proposed and that many verification issues will be handled with records, proof of purchase or targeted meter data where necessary. Staff also noted they already receive voluntary groundwater level and pumping data from some users that feeds modeling.

The GSA asked owners to email or call staff (contact details on the GSA web page) with claims and questions and reminded the public of a second community meeting on July 1, 2026 from 5:30 p.m. to 7:00 p.m. to review materials and answer additional questions.