There is established in the state treasury the ferry project special fund, into which shall be deposited revenues collected by the operators of the intra-island water ferry transportation system. Moneys in the ferry project special fund shall be used to offset costs incurred by the intra-island water ferry transportation system or demonstration project, or both; provided that no expenditure shall be made from, and no obligation shall be incurred against the fund in excess of its deposits. Moneys in the fund shall be expended by the department of transportation.