Neb. Rev. Stat. § 18-507

Whenever the governing body of any city or village shall have ordered the installation of a sewerage system and sewage disposal plant or the improvement or extension of an existing system, the fact that such order was issued shall be recited in the official minutes of the governing body. The governing body shall require that plans and specifications be prepared of such sewerage system and sewage disposal plant, or such improvement or extension. Upon approval of such plans, the governing body shall advertise for sealed bids for the construction of such improvements once a week for three weeks in a legal newspaper published in or of general circulation within such city or village, and the contract shall be awarded to the lowest responsible bidder.