Neb. Rev. Stat. §§ 16-653
For the purpose of paying the costs of grading the streets and alleys in a grading district in a city of the first class, exclusive of the intersection of streets and spaces opposite alleys therein, the mayor and city council shall have power, and may, by ordinance, cause to be issued bonds of the city, to be called District Grading Bonds of District No. ....., payable in not exceeding five years from date and to bear interest, payable annually or semiannually, with interest coupons attached, and that as nearly as possible an equal amount of the bonds shall be made to mature each year, and in such case shall also provide that such special taxes and assessments shall constitute a sinking fund for the payment of such bonds and interest. The entire cost of grading any such street or alley properly chargeable to any lots or lands within any such grading district, according to feet front thereof, may be paid by the owner of such lots or lands within fifty days from the levy of such special taxes or assessments. Upon payment, such lot or land shall be exempt from any lien or charge therefor.
Neb. Rev. Stat. §§ 16-653