Board sends Castello D27Amorosa winery use‑permit modification back to Planning Commission after water analysis discrepancies

The Napa County Board of Supervisors voted unanimously Tuesday to remand an appeal concerning the Castello D'Amorosa winery use‑permit modification so the Planning Commission can review an updated Water Availability Analysis (WAA) and prepare an advisory report.

The appeal was filed by Water Audit California after the Planning Commission on April 2 found the project categorically exempt under CEQA and approved the major modification (use permit major modification P1900459). Staff and the project’s consultants later identified discrepancies between the WAA that supported the Planning Commission approval and historic groundwater reporting submitted for the site.

Emily Hedge, the county project planner for the proposal, told the board staff requested historic water‑use data while preparing a condition of approval requiring the project to maintain the operational levels of an existing on‑site well referred to as “well number 2.” After reviewing the data submitted by the applicant, staff said it found the WAA’s baseline estimate of groundwater use did not match the county’s review of reported water production and metering data.

Hedge described the principal discrepancy as the WAA estimating roughly 16 acre‑feet per year of groundwater use while reported data for the same property year showed about 39 acre‑feet — a number near the documented recharge estimate of roughly 40.5 acre‑feet. Board members also cited other inconsistencies in the application materials, including differences between totals in the WAA and the applicant’s State Water Resources Control Board reporting, with one staff slide comparing a 27.17 acre‑feet total production figure to a 55.4 acre‑feet total reported figure for 2024.

Applicant counsel said the county and the applicant discovered operational changes — including that well number 2 had been used more heavily than characterized in earlier submittals — and that the applicant had moved quickly to correct reporting to the State Water Resources Control Board once the discrepancy was identified. The applicant also said it is updating meters and infrastructure to separate domestic, landscaping and vineyard irrigation water uses.

Appellant counsel Bill McKinnon argued the discrepancies were material and said that the board should grant the appeal and remand for full consideration; he added that the applicant’s prior state filings raised questions about compliance with state diversion permits and the public trust.

County staff recommended the remand so the Planning Commission could review a corrected WAA and prepare an advisory report addressing groundwater use, effects on public trust resources and any other topics the board wishes the commission to consider. The applicant supported the remand; the appellant objected to remand but argued the appeal should be granted.

After questions from supervisors about reporting, monitoring and the Scope of the WAA, Supervisor Amber Alessio moved to remand the matter to the Planning Commission for the updated WAA and advisory report. Supervisor Gallagher seconded; the motion passed unanimously.

The board directed staff and the Planning Commission to review the updated WAA, consider peer review, and include evaluation of groundwater use, wastewater, visitation and any CEQA or public‑trust implications in an advisory report to the board. The applicant will provide corrected water‑use data and staff will arrange peer review of the revised analysis before the matter returns to the board for resolution of the appeal.