(a) The territory of a part of a county that is not a part of an authority and that is designated by the commissioners court of the county may be added to an authority if:
(1) any part of the county is located in the authority or any part of an adjacent county is located in the authority;
(2) the commissioners court orders an election in the designated area under this section on whether the area should be added to the authority; and
(3) a majority of the votes received in the election favor the measure.
(b) In designating an area under this section, the commissioners court may not, to the extent practicable, divide a county election precinct.
(c) The commissioners court shall certify to the authority the result of an election in which the addition is approved.