Cal. Sts. & High. Code § 19053

Any person interested, who objects either to the formation of the district, or to the extent of the district, or 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 at or before the time set for the hearing of the petition. The clerk shall indorse on each protest the date of its filing with him, and at the time appointed for the hearing he shall present all protests so filed with him to the board of supervisors.