(a) In General.—The Secretary, on notification, in writing, by any Federal or State agency or appropriate historical or archeological authority that scientific, prehistorical, historical, or archeological data are being or may be irrevocably lost or destroyed by any Federal or federally assisted or licensed project, activity, or program, shall, if the Secretary determines that the data are significant and are being or may be irrevocably lost or destroyed and after reasonable notice to the agency responsible for funding or licensing the project, activity, or program—
(b) When Survey or Recovery Not Required.—
No survey or recovery work shall be required pursuant to this section that, in the determination of the head of the responsible agency, would impede Federal or federally assisted or licensed projects or activities undertaken in connection with any emergency, including projects or activities undertaken in anticipation of, or as a result of, a natural disaster.