Neb. Rev. Stat. § 2-3254.01

When determining the apportionment of benefits under section 2-3254 , the board shall also make a determination as to what portion of the project will result in special benefits to lands and property and such determination, if not appealed as provided in section 2-3255 , shall be conclusive as establishing the authority of the district to levy special assessments and issue bonds and warrants for such project.