The signatures of duly qualified electors of the City equal to ten (10) percent of the total votes cast for Mayor at the last preceding City election shall be necessary to order a referendum on any ordinance passed by the City Council, and the signatures of duly qualified electors of said City equal to fifteen (15) percent of the total votes cast for Mayor at the last preceding City election shall be necessary to propose any measure by initiative process. (Ord. 1319 § 6, amended, 1962)