(a) The board of supervisors shall not levy assessments pursuant to Section 19311 unless it has adopted an ordinance to do so. The board of supervisors shall place before the voters of the zone, either before the initial ordinance takes effect or within one year thereafter, the question whether the district shall be authorized to levy assessments.

If the majority of those voting disapprove of such authority, no subsequent ordinance levying assessments for any succeeding fiscal year shall be adopted by the board of supervisors without the prior approval of the voters of the zone.

Subsequent election or elections to secure such approval shall not be held more than once a year.