The provisions of section 401 of this title are made applicable alike to the completed and uncompleted portions of the Illinois and Mississippi Canal. Whenever the Secretary of the Army shall approve plans for a bridge to be built across said canal he may, in his discretion, and subject to such terms and conditions as in his judgment are equitable, expedient, and just to the public, grant to the person or corporation building and owning such bridge a right of way across the lands of the United States on either side of and adjacent to the said canal; also the privilege of occupying so much of said lands as may be necessary for the piers, abutments, and other portions of the bridge structure and approaches.