Upon the expiration of any harbor area lease upon tidal waters, the lessee may apply for a re-lease of the harbor area for a period not exceeding thirty years. The application shall be accompanied with maps showing the existing improvements upon the harbor area and the adjacent tidelands and with proper plans, drawings, and other data showing any proposed extensions or improvements of existing structures. Upon the filing of an application the department shall investigate the application and if it determines that the character of the wharves, docks, or other conveniences of commerce and navigation are reasonably adequate for the public needs and in the public interest, it shall by order fix and determine the terms and conditions upon which the re-lease shall be granted and the rate of rental to be paid, which rate shall be a fixed percentage during the term of the lease on the true and fair value in money of the harbor area as determined by the department.