70 ILCS 1205/2-10a
Any district may provide by referendum, or by resolution of the board, that the board shall be comprised of 7 commissioners. Any such referendum shall be initiated and held in the same manner as is provided by the general election law.
If a majority of the votes cast on the proposition is in favor of the 7-member board, or if the board adopts a resolution stating that it is acting pursuant to this Section in order to create a 7-member board, then whichever of the following transition schedules are appropriate shall be applied: At the election of commissioners next following by at least 197 days after the date on which the proposition to create a 7-member board was approved at referendum or by resolution, the number of commissioners to be elected shall be 2 more than the number that would otherwise have been elected.
If this results in the election, pursuant to Section 2-12 of this Act, of 4 commissioners at that election, one of the 4, to be determined by lot within 30 days after the election, shall serve for a term of 4 years or 2 years as the case may be, instead of 6 years, so that his term will expire in the same year in which the term of only one of the incumbent commissioners expires. Thereafter, all commissioners shall be elected for 6-year terms as provided in Section 2-12. If the creation of a 7-member board results in the election of either 3 or 4 commissioners, pursuant to Section 2-12a of this Act, at that election, 2 of them, to be determined by lot within 30 days after the election, shall serve for terms of 2 years instead of 4 years. Thereafter, all commissioners shall be elected for 4-year terms as provided in Section 2-12a of this Act.
In any district where a 7-member board has been created pursuant to this Section whether by referendum or by resolution, the number of commissioners may later be reduced to 5, but only by a referendum initiated and held in the same manner as prescribed in this Section for creating a 7-member board. No proposition to reduce the number of commissioners shall affect the terms of any commissioners holding office at the time of the referendum or to be elected within 197 days after the referendum. If a majority of the votes cast on the proposition is in favor of reducing a 7-member board to a 5-member board, then, at the election of commissioners next following by at least 197 days after the date on which the proposition was approved at referendum, the number of commissioners to be elected shall be 2 less than the number that would otherwise have been elected and whichever of the following transition schedules are appropriate shall be applied: (i) if this results in the election of no commissioners for a 6-year term pursuant to Section 2-12 of this Act, then at the next election in which 3 commissioners are scheduled to be elected to 6-year terms as provided in Section 2-12, one of the 3, to be determined by lot within 30 days after the election, shall serve for a term of 4 years or 2 years, as the case may be, instead of 6 years, so that his or her term will expire in the same year in which the term of no incumbent commissioner is scheduled to expire; thereafter, all commissioners shall be elected for 6-year terms as provided in Section 2-12; or (ii) if the reduction to a 5-member board results in the election of one commissioner to a 4-year term, pursuant to Section 2-12a of this Act, then at the next election in which 4 commissioners are scheduled to be elected to 4-year terms as provided in Section 2-12a, one of the 4, to be determined by lot within 30 days after the election, shall serve for a term of 2 years, instead of 4 years, so that his or her term will expire in the same year in which the term of only one incumbent commissioner is scheduled to expire; thereafter, all commissioners shall be elected for 4-year terms as provided in Section 2-12a.
70 ILCS 1205/2-10a