Whenever any property acquired for any of the purposes of this chapter, whether by agreement, grant, or eminent domain, either in fee or in any lesser estate or interest, is no longer necessary for use in connection with any improvement authorized to be constructed pursuant to this chapter, or whenever a lesser interest than is owned therein is sufficient for the construction, maintenance, and operation of any improvement, or whenever it is for any other reason in the public interest to do so, the property, any part thereof, or any interest therein may be leased, sold, exchanged, or otherwise disposed of or dealt with by the director in the manner, upon such terms, and subject to such reservations as are first approved by the commission.