Tennessee Code Title 64. Regional Authorities § 64-1-1109

(a) This part applies only to the counties of Lauderdale, Lake, Dyer, Obion, Madison, Weakley, Henry, Gibson, Carroll, Benton, Decatur, Hardin, Haywood, Crockett, Henderson, Chester, Tipton, Hardeman, Fayette and McNairy, which may, upon approval by a majority vote of the respective county legislative bodies, elect to participate in such programs as set out in this part; and, in the event such an election is made, this part applies to all counties making such an election.

(b) If any of such counties have previously elected to participate in, and have not withdrawn from, the programs of the Obion-Forked Deer Basin authority established by Acts 1972, ch. 806 or by Acts 1976, ch. 448, as amended, no further election shall be necessary to become a participating county in the authority created by this part; and such status as a participating county shall carry over and apply to the authority and its programs provided for in this part.