40 ILCS 5/13-703
A vacancy occurring in the membership of the Board shall be filled as follows:
If the vacancy is of an appointive member, the President of the Water Reclamation District shall designate a person to serve until the Board of Commissioners of the District appoints a member to fill the vacancy for the unexpired term. If the vacancy is of an elective office the remaining members of the Retirement Board shall designate an employee to serve the remainder of the unexpired term.
Any employee who leaves the service of the District or who shall be or become a member or beneficiary of any public annuity or pension fund other than the Fund created by this Article, shall automatically become ineligible to elective membership on the Board, and if such person is an elected member of the Board, that office shall automatically become vacant and shall be filled as herein provided for the filling of vacancies. This Section shall not apply to pensions or benefits granted by the Government of the United States or by any state for service in the military or naval forces of the United States.
40 ILCS 5/13-703