The powers granted by sections 16-6,106 to 16-6,109 may be exercised in whole or in part and from time to time as the city council may in its discretion determine but before general obligation bonds are issued for the purposes of sections 16-6,106 to 16-6,109, the city council shall hold a public hearing after three weeks' notice published in a legal newspaper in or of general circulation in such city, and the referendum provisions of the Municipal Initiative and Referendum Act shall apply to any ordinance or resolution authorizing issuance of such bonds. The program for implementation of the plan may be adopted and carried out in parts, sections, or stages.