Municipalities which are not initial members of the District may, upon the requisite approval by its voters as set forth in this section and the approval of the Board of Commissioners, become a member of the District. The legislative branch of any nonmember municipality which desires to be admitted to the District shall make application for admission to the Board of Commissioners. The Board of Commissioners may, in its sole discretion, determine the terms and conditions of admission, which terms and conditions shall be in the best interests of the District. If a majority of the voters of the petitioning municipality present and voting at an annual or special meeting of such municipality duly warned for such purpose shall vote to approve this chapter and the terms and conditions for admission, the vote shall be certified by the clerk of that municipality to the Secretary of the District. Thereafter, the Board may, by resolution, admit such municipality upon finding that such terms and conditions have been or will be satisfied. Immediately upon joining the District, the new member municipality shall appoint a commissioner and alternate commissioner as provided in subchapter 2 of this chapter.