That (a) all sums received and deposited in each such special fund shall be held inviolate and applied by the municipality solely for the payment of the principal of, and interest on, the bonds issued for the financing of the identified improvement, except as otherwise provided herein. The amounts collected and deposited in each such special fund from the first improvement assessments in connection with any improvement, in excess of maturing principal and interest on the bonds, for the purpose of creating a "debt service reserve" as provide in Section 6 (6A.06), hereof, shall be held in the special fund for that purpose. If collections of the first annual improvement assessments shall fail to produce a sum sufficient to provide the minimum "debt service reserve" required by Section 6 (6A.06) hereof, the next annual improvement assessments shall be fixed at such levels as may be necessary to constitue said minimum "debt service reserve" after providing for the current year's principal and interest maturities. If, at the time of making subsequent improvement assessments, the sum held in a special fund as the "debt service reserve" shall exceed the level herein specified, such excess may be taken into account in calculating the improvement assessments for the current year; and if the amount so held in said "debt service reserve" is below said specified level, the next annual improvement assessments shall be increased to constitute the "debt service reserve" at said minimum level. In making improvement assessments for the year preceding the final maturing of bonds for an improvement, the governing body may take into account, and make allowance for, the amount held in the special fund of the particular improvement as a "debt service reserve." If the governing body shall miscalculate and provide funds insufficient to pay the final maturing principal and interest, it shall make subsequent improvement assessments upon the benefited properties sufficient to make up the deficiency, including interest to date of payment. If the procedures required by this Act shall result in a surplus after payment of the bonds and all interest thereon, such surplus shall be refunded, pro rata, to the owners of benefited properties of record at the date such surplus is ascertained by the governing body to exist.
(b) Notwithstanding other provisions of this Act (Article), no improvement assessment may be increased more than 5 per cent on account of insufficient collection of improvement assessments. The municipality shall provide from its general funds, by issuance of bonds as provided by general law for public works if necessary, such additional funds as may be required on account of insufficient collection of improvement assessments to pay principal and interest on the improvement assessment bonds when due. Whatever amount of delinquent improvement assessments are eventually collected by enforcement of liens or by other means shall be applied to the source of such additional funds, the general funds of the municipality, or to retire any bonds that were issued. [As added by Priv. Acts 1970, ch. 276, § 15]