Measures passed by Council shall, unless a later date be specified therein, take effect as follows:
   l.   Measures to which the referendum is not applicable, immediately upon certification by the Clerk of publication.
   2.   Emergency measures, to which Council has by a vote of not less than five members added a section declaring the necessity to put such measure into immediate force and effect in order to preserve the public peace, order, safety, health, or welfare of the municipality, or to provide for the usual daily operation of a department or office of the municipality; and also stating specifically the reason and nature of such necessity, immediately upon certification by the Clerk of publication; but no public utility franchise or rate ordinance shall be passed as an emergency measure.
   3.   All other measures shall take effect and be in force 45 days after the certification by the Clerk of their publication under the requirements of this Charter, unless suspended by the filing of a valid referendum petition.