Neb. Rev. Stat. § 14-534

Before any street, avenue, alley, or thoroughfare is graded within a city of the metropolitan class, the city engineer shall make a careful and detailed estimate of the total cost of such grading, and shall report such estimate to the city council as an approximate estimate of such cost. If such estimate is approved by the city council, a contract may be let for the grading in the manner provided for letting improvement contracts, except that such contract shall not exceed in total amount the approved approximate estimate.