Ala. Code § 11-3A-5

The powers authorized under this chapter shall be effective in a county only after an affirmative vote of a majority of the qualified electors of the county residing in the unincorporated areas of the county and voting in a referendum election held on the question of whether the powers authorized under this chapter shall be effective in the county. Except as provided in subsection (h) of Section 11-3A-2, the election shall be called upon resolution adopted by affirmative vote of the majority of the members of the county commission. The referendum election shall be conducted in accordance with the election laws of the state and may be held only in conjunction with a primary, general, or special election held for another purpose in the county. In no case may any election authorized by this chapter be held more often than once every 48 months.