The Port District may lease to others for any period of time not to exceed 99 years, upon such terms as the Board may determine, any of its real property, rights of way or privileges, or any interest therein, or any part thereof, suitable for industrial, manufacturing, commercial or harbor purposes which, in the opinion of the Board, is no longer required for its primary purposes in the development of port and harbor facilities for the use of public transportation, or which may not be needed immediately for such purposes. But where such leases in the opinion of the Board will aid and promote such purposes in conjunction with such leases, the Port District may grant rights of way and privileges across property of the Port District. Such rights of way and privileges may be assignable and irrevocable during the term of any lease and may include the right to enter upon the property of the Port District to do such things as may be necessary for the enjoyment of leases, rights of way and privileges. Such leases may contain such conditions and retain such interest therein as the Board deems for the best interest of the Port District.