Petition by 60% of property owners for improvements

If the owners of not less than sixty percent of the frontage upon any street, alley, or highway designated by them or of sixty percent of the area of land designated by them as a proposed improvement district, file with the council a petition duly acknowledged by the owners requesting the construction of special improvements, together with the surveys, maps, plans and other preliminary data and estimates mentioned in section 12-10, in the case of a proceeding initiated by the council, the council may reject or accept the petition. If the petition is accepted, the council shall proceed in the same manner as though the plan for such improvements had been initiated on its own motion, and the cost of the preliminary surveys, maps and other data, if not in excess of the estimate therefor stated in the petition, shall be deemed part of the cost of the improvement; provided, that upon such petition the council shall not have the power to abandon the proceedings or make any change or modification of the plans or the details or specifications for the proposed improvements without the written and duly acknowledged consent of the owners of not less than sixty percent of the frontage or area of the land to be assessed; except that the council may decline to acquiesce in or may modify any part of the plan which contemplates the payment by the County of any part of the cost of acquiring new land or of any part of the cost of improving any main or general thoroughfare, and in such event, if the owners of not less than sixty percent of the frontage or property to be assessed agree in writing to the change or modification, the council shall be bound to proceed with the plan as so modified.