As soon as practicable after September 1, 1965, and following the transfer to the Secretary of the Interior by the Secretary of the Army of jurisdiction over those lands and interests therein within the boundary generally depicted on the drawing described in section 460o–1 of this title which, in the opinion of the Secretary of the Interior, constitute an efficiently administrable unit, the Secretary of the Interior shall declare establishment of the area by publication of notice thereof in the Federal Register. Such notice shall contain a detailed description of the boundaries of the area which shall encompass, to the extent practicable, the lands and waters shown on said drawing. Prior to such establishment, the Secretary of the Interior shall administer such transferred lands and waters, consistent with the construction of the project, for purposes in contemplation of the establishment of the area pursuant to this subchapter.

The Secretary of the Interior may subsequently make adjustments in the boundary of the area by publication of the amended description thereof in the Federal Register and acquire, by such means as he may deem to be in the public interest, including an exchange of excluded for included lands or interests therein with or without the payment or receipt of money to equalize values, additional lands and interests therein included in the area by reason of the boundary adjustment: Provided, That the area encompassed by such revised boundary shall not exceed the acreage included within the detailed boundary first described pursuant to this section.

On lands acquired pursuant to this subchapter for recreation purposes, the Secretary of the Army, with the concurrence of the Secretary of the Interior, may permit the continuance of existing uses consistent with the purposes of this subchapter.