Tenn. Code § 7-35-408
Commissioners shall be appointed by majority vote of the governing body of the city or town, the original appointees to serve from the date of appointment for one (1), two (2), three (3), four (4) and five (5) years, respectively, from the next succeeding July 1, unless a member of the governing body of the city is appointed to serve on the board, and in that event, the original appointees to serve from the date of appointment for one (1), two (2), three (3), and four (4) years, respectively, from the next succeeding July 1. Each successor to a retired member of the board shall be appointed for a term of five (5) years in the same manner, at the next regular meeting of the governing body of the city in June next preceding the expiration of the term of office of the retiring member. Appointments to complete unexpired terms of office, vacant for any cause, shall be made in the same manner as the original appointments.
T.C.A. § 7-35-408