The unit designated as Hogan Dam and Reservoir, substantially in accordance with the recommendations of the Chief of Engineers in House Document No. 545, 78th Congress, Second Session, and authorized by act of Congress approved December 22, 1944, Public Law 534, 78th Congress, Second Session, subject to such further modifications thereof as the department may adopt, and such unit may be constructed, maintained, and operated separate and apart from any or all other units thereof.