(a) In General.—Before any Federal agency undertakes the construction of a dam, or issues a license to any private individual or corporation for the construction of a dam, it shall give written notice to the Secretary setting forth the site of the proposed dam and the approximate area to be flooded and otherwise changed if construction is undertaken.

(b) Dams With Certain Detention Capacity or Reservoir.—With respect to any flood water retarding dam that provides fewer than 5,000 acre-feet of detention capacity, and with respect to any other type of dam that creates a reservoir of fewer than 40 surface acres, this section shall apply only when the constructing agency, in its preliminary surveys, finds or is presented with evidence that historical or archeological materials exist or may be present in the proposed reservoir area.