Except such resolutions or ordinances as may be necessary for the immediate preservation of the public peace, health, or safety, or support of the county government and its existing public institutions; which provide for an election or hearing on an improvement or assessment; or which call for bids which take effect upon the passage and publication thereof, every resolution or ordinance passed by a board shall take effect on the twentieth day after its completed publication unless suspended by operation of a referendum.
SDCL 7-18A-8