Vacancies on the Commission shall be filled, within thirty days, by appointment of the same official who appointed the prior holder of the position. The provisions of Section 83102 (b) are not applicable to the filling of vacancies. Appointments to fill vacancies shall be for the unexpired term of the member or chair whom the appointee succeeds. A vacancy or vacancies shall not impair the right of the remaining members to exercise all of the powers of the board. Three members shall constitute a quorum.