William J. Baxley, Atty. Gen., Myron H. Thompson, Sp. Asst. Atty. Gen., Henry H. Caddell, Asst. Atty. Gen., Chief Environmental Protection Dir., Frederick S. Middleton, III, Montgomery, Ala., for plaintiffs-appellants., Philip K. Maxwell, Asst. Atty. Gen., Austin, Tex., amicus curiae for State of Tex., David C. Short, David D. Beals, Asst. Attys. Gen., Frankfort, Ky., amicus curiae for Com. of Ky., Jan E. Chatten, Deputy Atty. Gen., Los Angeles, Cal., amicus curiae for State of Cal., Wayman G. Sherrer, U. S. Atty., Charles D. Stewart, William D. Mallard, Jr., Asst. U. S. Attys., Birmingham, Ala., Kent Frizzell, Asst. Atty. Gen., Martin Green, Chief, Pollution Control Sec., James R. Walpole, Atty., Land & Nat’l Resources Div., Dept. of Justice, Washington D. C., Robert H. Marquis, Gen. Counsel, Tenn. Valley Auth., Herbert S. Sanger, Jr., Assoc. Gen. Counsel, Beauchamp E. Brogan, Asst. Gen. Counsel, Justin M. Schwamm, Atty., Knoxville, Tenn., Wallace H. Johnson, Jacques B. Gelin, Larry G. Gutterridge, Dept, of Justice, Washington, D. C., for defendants-appellees.