Oregon Revised Statutes Public Health and Safety § 450.055

(1) The officers of the district shall be the district board, consisting of three or five members, and a secretary appointed by the board.

(2) Except as to those members of the board who are elected on formation and those members who are elected at an election when the number of board members is increased to five, the term of office of each elected member shall be four years.

(3) Vacancy in the membership of the board shall occur by reason of the occurrence of any event listed in ORS 236.010 or, unless excused, by failure to attend three successive regular board meetings. The district board shall fill any vacancy on the board as provided in ORS 198.320.