The authority shall lease or grant concessions for the use of its facilities or various portions of such facilities to one or more operators to provide for the efficient operation of the facilities. All leases or concessions shall be let on a competitive basis and no lease or concession shall run for a period in excess of thirty years. In granting any lease or concession, the authority shall retain such control of the facilities as may be necessary to insure that the facilities will be properly operated in the public interest and that the prices charged are reasonable.