Exclusive of special levies permitted by this Charter, the City Council shall not levy a property tax in excess of one percent of the assessed value of taxable property in the City for municipal purposes, unless authorized by a two-thirds vote at a City election.
   There shall be levied and collected at the time and in the same manner as other property taxes for municipal purposes are levied and collected as additional taxes, if no other provision for payment thereof is made:
   (a)   A tax sufficient to meet all liabilities of the City for principal and interest of all bonds or judgments due and unpaid, or to become due during the ensuing fiscal year; and
   (b)   A tax sufficient to meet all obligations of the City to the Public Employees' Retirement System, or other system for the retirement of City employees due and unpaid or to become due during the ensuing fiscal year.
   Special levies, in addition to the above, may be made annually, based on City Council approved estimates, for specific purposes as may be approved by the City Council. The proceeds of any such special levy shall be used for no other purpose than that specified.