In any case in which there is no applicable law with respect to a transportation or utility system, the head of the Federal agency concerned shall, within four months after the date of filing of any final Environmental Impact Statement, make recommendations, for purposes of section 3166(b) of this title, to grant such authorizations as may be necessary to establish such system, in whole or in part, within the conservation system unit concerned if he determines that⁠—

(1)  such system would be compatible with the purposes for which the unit was established; and

(2)  there is no economically feasible and prudent alternative route for the system.