On September 26, 1991 (the effective date of Public Act 87-738), the terms of all the current Board members shall expire. Within 60 days after that date, the mayor or president, as the case may be, of each of the following municipalities, with the advice and consent of the corporate authorities of that municipality, shall appoint one member to the Board, for a total of 7 members: Harvey, Flossmoor, Lansing, South Holland, Homewood, East Hazel Crest, and Glenwood. Two members shall serve for terms expiring June 1, 1993, 2 members for terms expiring June 1, 1994, and 3 members for terms expiring June 1, 1995. Terms of the members shall be determined by lot at the first meeting of the Board after all appointments are made. Within 60 days after the territory of a municipality becomes part of the metropolitan area as provided in Section 55-15, the mayor or president, as the case may be, of that municipality, with the advice and consent of the corporate authorities of that municipality, shall appoint one member to the Board, who shall be an additional member; that additional member shall serve an initial term expiring on June 1 of the second calendar year after appointment. The successors of the members shall be appointed in like manner for 3 year terms from the date of appointment, except in case of an appointment to fill a vacancy. The Board may, by ordinance, appoint from one to 5 additional members of the Board, those additional members to serve at the pleasure of the Board.