Neb. Rev. Stat. § 14-536

Upon the completion of any grading of a street, avenue, alley, or thoroughfare, the city council of a city of the metropolitan class shall levy special assessments in the manner provided in sections 14-501 to 14-566 , to the extent of the benefits, to cover the total costs of such grading. Special assessments so levied shall be made payable as provided in section 14-537 . All installments shall draw interest at a rate not to exceed the rate of interest specified in section 45-104.01 , as such rate may from time to time be adjusted by the Legislature, from the time of levy until due, and the rate specified in section 45-104.01 , as such rate may from time to time be adjusted by the Legislature, whenever such installments become delinquent. All such special assessments and all interest accruing on such special assessments shall constitute a sinking fund and shall be used only for the purpose of paying the interest on the bonds issued in that connection as such interest accrues and of paying the principal sum of the bonds at the maturity of such bonds.