(a) an operation and maintenance fund out of which there shall be paid the usual and necessary expenses for the operation and maintenance of the project facilities;
(b) a renewal and replacement fund sufficient to assure that the project facilities, including equipment, shall be kept in good repair and working order;
(c) a bond and interest fund which shall be sufficient to provide for the payment of the principal of and the interest on the bonds as they mature and accrue, including a reasonable sum for the creation of a bond reserve fund to assure the payment of such bonds and the interest therein in the event that sufficient funds therefor are not otherwise available; and
(d) a contingent fund to provide for unforeseen contingencies arising in the operation of the project facilities. Any surplus funds remaining after making the foregoing allocations shall be dealt with as may be directed by the resolution of the board of supervisors whereunder such bonds are issued, for the repayment of advances received from any source, for the payment of any maturities of principal and interest of such bonds, for the improvement of the port and/or harbor facilities for which such bonds were issued, or for the retirement of the outstanding bonds according to their terms.