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
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
, or any other law or regulation relating to either employment or compensation.