Members of the Board shall be appointed for a term of five years, excepting that when the Board shall first be created, three members shall be appointed for a term of five years, three members for a term of four years and three members for a term of three years. The Board shall not carry out its business without having five members present. Members shall be removable for cause by the appointing authority upon written charges and after public hearing. Vacancies shall be filled for the unexpired term of any member whose term becomes vacant.