A vacancy on the board shall occur and shall be filled as provided in chapter
42.12 RCW. In addition, if a commissioner is absent from three consecutive scheduled meetings unless by permission of the board, the office may be declared vacant. However, such an action shall not be taken unless the commissioner is notified by mail after two consecutive unexcused absences that the position will be declared vacant if the commissioner is absent without being excused from the next regularly scheduled meeting.