Cal. Water Code § 55150

Any person interested, including any freeholder or qualified voter resident within the proposed district or the owner of any real or personal property located in the proposed district, objecting to the formation of the district, to the extent of the district, to the proposed improvement, or to the inclusion of his property in the district, may file a written protest, setting forth his objections, with the clerk of the board of supervisors at or before the time set for the hearing of the petition.