All laborers and mechanics employed in the construction of any part of the project, or in the operation, maintenance, or replacement of any part of the Hoover Dam, shall be paid not less than the prevailing rate of wages or compensation for work of a similar nature prevailing in the locality of the project. In the event any dispute arises as to what are the prevailing rates, the determination thereof shall be made by the Secretary of the Interior, and his decision, subject to the concurrence of the Secretary of Labor, shall be final.