In order to enable and empower the Secretary of the Army, the Secretary of the Interior, or the Board to carry out the authority conferred in this chapter, in the most economical and efficient manner, he or it is authorized and empowered in the exercise of the powers of national defense in aid of navigation, and in the control of the flood waters of the Tennessee and Mississippi Rivers, constituting channels of interstate commerce, to exercise the right of eminent domain for all purposes of this chapter, and to condemn all lands, easements, rights of way, and other area necessary in order to obtain a site for said Cove Creek Dam, and the flowage rights for the reservoir of water above said dam, and to negotiate and conclude contracts with States, counties, municipalities, and all State agencies and with railroads, railroad corporations, common carriers, and all public utility commissions and any other person, firm, or corporation, for the relocation of railroad tracks, highways, highway bridges, mills, ferries, electric-light plants, and any and all other properties, enterprises, and projects whose removal may be necessary in order to carry out the provisions of this chapter. When said Cove Creek Dam, transmission line, and power house shall have been completed, the possession, use, and control thereof shall be intrusted to the Corporation for use and operation in connection with the general Tennessee Valley project, and to promote flood control and navigation in the Tennessee River.