Neb. Rev. Stat. §§ 16-655
The aggregate amount of bonds issued under sections 16-653 and 16-654 in any one year shall not exceed fifty thousand dollars and shall not be sold for less than their par value. If any assessment or part thereof shall fail or for any reason be invalid, the mayor and city council may make such further assessments upon such lots or lands, as may be required, and collect from the owners the cost of any grading properly chargeable. No street, avenue, alley, or lane shall be so graded until the damages to property owners, if any, shall be ascertained by three disinterested property owners to be appointed by the mayor and city council and the proceedings to be the same in all respects as provided in section 16-615 for cases of change of grade.
Neb. Rev. Stat. §§ 16-655