(a) Any county in the eastern grand division not a member of the authority may become a member by:
(1) Notifying the board of its desire to become a member;
(2) Adopting a resolution by a two-thirds (⅔) vote of the county legislative body; and
(3) Contributing funds in an amount to be determined by the board, which shall not exceed the highest contribution by any county already a member as adjusted for inflation or deflation by the consumer price index, all cities average, published by the United States department of labor.
(b) Upon approval by the board and the county legislative body of the county seeking to become a member, the county shall become a member of the authority when the authority receives the necessary contribution. When a county is added as a member of the authority, the board shall cause the resolution of the county legislative body providing for addition of the county as a member of the authority to be filed with the secretary of state as an addendum. New members shall be entitled to membership on the board. The county mayor of any such county, or the county mayor's designee, shall become a member of the board for an initial term of office to be established by the board.