SECTION 13.10.  DISPOSAL OF UTILITY PLANTS AND PROPERTY.
   Unless approved by a majority vote of the electors voting thereon at a regular or special election, the city shall not sell, exchange, lease or in any way dispose of any property, easement, equipment, privilege, or asset belonging to and appertaining to any municipally owned utility.  All contracts, negotiations, licenses, grants, leases or other forms of transfer in violation of this section shall be void.  The prohibition of this section shall not apply to the sale or exchange of any article of machinery or equipment of and city-owned utility which are worn out, or useless, or which have been or which, with advantage to the service, could be replaced by new and improved machinery or equipment.