There is hereby established an Architectural Review Board, to be composed of three members chosen by the Commissioner of Public Property and Building and approved by Council. Each member of the Board shall serve for a three-year term. However, the members of the first such Board shall have terms of one, two or three years, after which the three-year individual term will take effect. Vacancies shall be filled by appointment of the Commissioner, for the unexpired term, with the approval of Council.