Pub. Util. Code, § 28793

The acts of the board shall be expressed by motion, resolution, or ordinance. No ordinance shall be passed by the board on the day of its introduction, nor within three days thereafter, nor at any time other than a special, regular, or adjourned regular meeting. No ordinance, resolution, or motion shall have any validity or effect unless passed by the affirmative votes of a majority of the directors. No ordinance shall take effect until the expiration of 30 days following its adoption, except the following which shall take effect upon adoption: an ordinance relating to an election, or to the issuance or sale of bonds, or to the levying or collection of taxes, or the fixing of fares; or an ordinance necessary for the immediate preservation or protection of the property, interests, or welfare of the district, which shall contain a specific statement showing its urgency, and which shall be passed by two-thirds of the total vote of the directors. All ordinances except those which take effect upon their adoption shall be subject to referendum in the manner provided by law for the legislative acts of boards of supervisors of counties.