The memorial authorized herein shall be constructed in general, in accordance with the plan approved by the United States Territorial Expansion Memorial Commission on May 25, 1948. The Secretary of the Interior is authorized to enter into such contracts as may be necessary to carry out the purposes of sections 450jj to 450jj–9 of this title. The Secretary is also authorized to employ, in his discretion, by contract or otherwise, landscape architects, architects, engineers, sculptors, artists, other expert consultants, or firms, partnerships, or associations thereof, and to include in any such contract provision for the utilization of the services and facilities, and the payment of the travel and other expenses, of their respective organizations, in accordance with the usual customs of the several professions and at the prevailing rates for such services and facilities, without regard to the civil-service laws or regulations, chapter 51 and subchapter III of chapter 53 of title 5, section 6101 of title 41, or any other law or regulation relating to either employment or compensation.

The Secretary of the Interior, in connection with the construction and operation of the memorial, is authorized to grant such easements as are in the public interest, and, in his discretion, to convey to the city of Saint Louis for above-ground parking structures, under such terms and conditions as he may consider to be compatible with maintaining the integrity, appearance, and purposes of said memorial, such portion of the historic site as may in his judgment be excluded therefrom without detriment thereto, subject, however, to reversion of such portion of the historic site to the United States if such excluded area ceases to be used for parking purposes by said city.

The Secretary of the Interior is authorized to grant easements for the purpose of erecting under-ground structures suitable for public protection under such terms and conditions as he may consider to be compatible with maintaining the integrity, appearance, and purposes of said memorial.