; (vi) not more than 2 representatives from an Indian tribe or tribal organization chosen in a process determined, in consultation with Indian tribes, by the Secretary for each of clauses (iv) and (v); and (vii) not more than 5 nongovernmental members with relevant expertise appointed, after the date on which the members are first appointed under clauses (i) through (v), by a majority vote of the State representatives appointed under clause (iv). (B) Effect Nothing in this paragraph requires a State to participate in the Task Force. (4) Co-chairs The Co-Chairs of the Task Force shall be— (A) the Federal representative described in paragraph (3)(A)(i); and (B) 1 State representative appointed under paragraph (3)(A)(iv), to be selected by a majority vote of those State representatives. (5) Date of initial appointment (A) In general The members of the Task Force shall be appointed not later than 180 days after the date on which the study is completed under subsection (c). (B) Notification On appointment of the members of the Task Force, the Co-Chairs of the Task Force shall notify the Chairs and Ranking Members of the Committees on Environment and Public Works of the Senate and Natural Resources of the House of Representatives. (6) Vacancies Any vacancy in the members appointed to the Task Force— (A) shall not affect the power or duty of the Task Force; and (B) shall be filled not later than 30 days after the date of the vacancy. (7) Meetings The Task Force shall convene— (A) not less frequently than twice each year