The Secretary of the Interior may in connection with irrigation projects under the reclamation Act of June seventeenth, nineteen hundred and two, not exceeding one hundred and sixty acres in each case, survey and subdivide the same into town lots, with appropriate reservations for public purposes: Provided, That, whenever, in the opinion of the Secretary of the Interior, it shall be advisable for the public interest, he may dispose of town sites in excess of one hundred and sixty acres.