The City Council may, from time to time, either on its own action of a petition of interested property owners, after, public notice and hearing as provided by law, amend, supplement, change, modify or repeal the boundaries or regulations herein or subsequently established.

If such proposed amendment, supplement, change, modification or repeal is petitioned for by interested property owners, said petition shall be signed by the owners of fifty (50) percent of the area of all the real estate described in said petition, and also by owners of fifty (50) percent of the area of all real estate lying outside of said tract, but within two hundred (200) feet of the boundaries thereof, intervening streets and alleys not to be included in computing such two hundred (200) feet.

Whenever any amendment, supplement, change, modification or repeal of this Ordinance is proposed, such proposed amendment, supplement, change, modification or repeal shall first be submitted to the Planning and Zoning Commission of the City of Riverdale, which shall within thirty (30) days after the date of the receipt thereof report back to the City Council indicating approval or disapproval thereof. If the report of the Planning and Zoning Commission on such proposed amendment, supplement, change, modification or repeal is unfavorable or in the event of a protest against such proposed amendment, supplement, change, modification or repeal signed by the owners of twenty (20) percent or more of the area of all real estate lying outside the tract included in such proposed change, but within two hundred (200) feet, such amendment shall not become effective except by the favorable vote of at least three-fourths (3/4) of all the members of the Council. The provision of the statute relative to public hearing and official notice shall apply to all changes or amendments. (Public hearing cannot be held until at least fifteen (15) days has elapsed after publication of the notice). If any area is hereafter transferred to another district by a change in district boundaries by an amendment, supplement, change, modification or repeal, as above provided, the provision of this Ordinance in regard to buildings or premises existing at the time of the passage of this Ordinance shall apply to building or premises exiting at the time of passage of such amendment in such transferred area.

It shall be the duty of the City Council to act upon such proposed amendment, supplement, change, modification or repeal within thirty (30) days after receiving the report from the Planning and Zoning Commission.