To make an investigation of conditions within the Port District and to prepare and adopt a comprehensive plan for the development of port facilities for the Port District. In preparing and recommending changes and modifications in existing harbor and airport facilities, or a comprehensive plan for the development of such port facilities, as above provided, the Port District if it deems desirable may set aside and allocate an area or areas, within the lands owned by it, to be leased to private parties for industrial, manufacturing, commercial, or harbor purposes, where such area or areas in the opinion of the Board, are not required for primary purposes in the development of harbor and port facilities for the use of public water, land, and air transportation, or will not be needed immediately for such purposes, and where such leasing in the opinion of the Board will aid and promote the development of terminal and port facilities.