Any city, county, or city and county acting jointly, or authorized port or harbor agency may enter into contracts, leases or agreements with the board upon such terms or conditions and for such purposes relating to the improvement, operation, development, and expansion of any port, harbor, or inland waterway, or any part thereof as they deem advisable and may agree upon, and, without limiting the generalities of the foregoing, authority is hereby granted to any city, county, or city and county acting jointly, or authorized port or harbor agency to prepare and submit to the board in the manner set out in Section 59-5-15, a plan for the improvement, operation, development or expansion of such port, harbor, waterway or any part thereof. The board shall cause an independent determination and appraisal to be made of such plan, and if the board shall find and determine that such plan is practical and feasible and is in the public interest, and that the revenues to be derived therefrom will, over a period of time, be sufficient to service and retire any bonds issued to complete such planned development, then the board, in its discretion, may negotiate with such city and county or other authorized port or harbor agency on the terms of a contract or agreement for the issuance of bonds necessary to complete such planned development. The board may modify the proposed plan for the improvement, operation, development, or expansion of such port, harbor, or waterway, or any part thereof, and may impose such terms and conditions as, in its discretion, it may require to protect the interest of the state.