Hiller v. Marin Municipal Water Dist.

── Hiller v. Marin Municipal Water Dist. ── Court: California Court of Appeal Date: June 02, 2026 Category: General Filed 5/13/26; certified for publication 6/2/26 (order attached) IN THE COURT OF APPEAL OF THE STATE OF CALIFORNIA FIRST APPELLATE DISTRICT DIVISION ONE TOVE HILLER, Plaintiff and Appellant, v. MARIN MUNICIPAL WATER DISTRICT, (Marin County Super. Ct. No. CV0000996) Defendant and Respondent. Plaintiff and appellant Tove Hiller filed a complaint and ordinary mandamus proceeding challenging increased water rates adopted by the Marin Municipal Water District (District). The District interposed a demurrer, which the trial court sustained without leave to amend on the ground her claims were foreclosed by the final judgment in the District’s previously filed validation action under Code of Civil Procedure sections 860 through 870. On appeal, Hiller contends: (1) the District’s use of the validation statutes to insulate its water rates from further judicial review is contrary to the underlying purposes of article XIII D, section 6 of the California Constitution (Proposition 218); (2) her due process rights were abridged because neither she nor her attorney were personally notified of the District’s validation action; and (3) the plain language of Government Code section 1 53759, 1 which requires use of the validation statutes to challenge any ordinance, resolution or motion adopting “a fee or charge for water or sewer service,” does not bar her mandamus claims challenging the water rates on substantive constitutional grounds. We affirm. BACKGROUND Adoption of the Rate Ordinance On May 16, 2023, the District Board of Directors adopted Ordinance No. 464, establishing water service rates to remain in effect from July 1, 2023, through June 30, 2027. The ordinance recites compliance with the procedural and substantive requirements of Proposition 218, including conducting a cost-of-service analysis, providing notice to the public, and conducting a public hearing. It became effective 30 days after adoption. 2 The Water District’s Validation Action The following month, the District filed a validation action. The complaint alleged in detail the procedure utilized by the District’s independent rate consultant who assisted the District with analyzing its service costs and establishing cost-based rates allocating service costs proportionately to properties within its service area, using the District’s financial data, historical water sales, revenue requirements, and cost projections, as well as its specific customer water usage data and information. In making recommendations on tiered water rates, the consultant used the “ ‘base/extra capacity method,’ ” which is a methodology 1All further statutory references are to the Government Code unless otherwise indicated. 2 Before its adoption, Hiller filed a government claim on behalf of herself and a similarly situated class, claiming the District’s water fees violated Proposition 218 and requesting refunds. She filed an updated claim after the District adopted the rate ordinance. 2 used across California and promulgated by the American Water Works Association, refined to address the District’s particular customer usage patterns. The complaint alleged the increased rates were supported by the consultant’s study, which identified the District’s revenue requirements given current and projected expenses, and allocated those costs to users based on their proportional cost of service. The complaint in the validation action further alleged the District mailed notice of the proposed rates and charges in accordance with Proposition 218 to the record owner of any parcel upon which the water rates and charges were to be imposed, and to a