When damages have been agreed upon, allowed or awarded for laying out, widening, altering or vacating township or district roads, or for payments for right-of-way in aiding the State in connection with the construction of State highways or in connection with the construction of federal aid roads or such roads as are constructed with the aid of federal grants or loans, or for ditching to drain township or district roads, the amounts of such damages and interest on orders issued in payment of such damages shall be included in the next succeeding tax levy provided for in Section 6-501 of this Code, and may be in addition to and in excess of the maximum levy and rate of extension of taxes for road purposes authorized under Section 6-501, and when collected, shall constitute and be held by the treasurer of the district as a separate fund to be paid to the parties entitled thereto. The highway commissioner, or the township board of trustees or highway board of trustees, as the case may be, at the time of certifying the general tax levy for road purposes within the district, shall include and separately specify in such certificate the amount necessary to be raised by taxation for the purpose of paying such damages. Upon the approval by the county board of the amount so certified, when required in Section 6-501, the county clerk shall extend the same against the taxable property of such district, provided the amount shall not be extended at a rate in excess of .033% of value, as equalized or assessed by the Department of Revenue. The foregoing limitations upon tax rates may be increased or decreased under the referendum provisions of the General Revenue Law of Illinois.