Neb. Rev. Stat. § 31-220

The drainage supervisors, any time after receiving any petition as provided in section 31-204 , may authorize any appraisers or employees to go upon the lands affected for the purpose of examining the same and making a survey thereof. After the matter has been fully determined by the board or by the court on appeal, and condemnation or purchase money paid, the supervisors may authorize all contractors with their servants, teams, tools, instruments or other equipment to go upon the lands or lots for the purpose of constructing any ditch or ditches, drain or drains, and for this purpose may designate some responsible person to supervise the work.