The department may provide in the proceedings authorizing the issuance of bonds or may otherwise agree with the purchasers of bonds regarding the deposit of all moneys constituting the construction fund and the toll revenue fund and provide for the deposit of the money at such times and with such depositaries or paying agents and upon the furnishing of security as meets with the approval of the purchasers of the bonds so long as the depositaries and security provided for or agreed upon are qualified and eligible in accordance with the requirements of law.