An emergency measure is one which is necessary for the immediate preservation of the peace, health or safety of the City and one which is passed by the affirmative vote of three-fourths of the members of the City Council. An emergency measure shall take effect immediately upon its passage, provided it states in a separate section the reason it is necessary that it should become immediately operative. An emergency provision may be added to a proposed ordinance or resolution upon its final passage at the same meeting it is introduced upon the affirmative vote of three-fourths of all the members of the City Council.