Whenever the city council of a city of the metropolitan class shall have ordered the installation of a sewerage system, including any storm sewer 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 city council. The city council shall require that plans and specifications be prepared of such sewerage system, including any storm sewer system, and sewage disposal plant, or such improvement or extension. Upon approval of such plans, the city council shall advertise for sealed bids for the construction of such improvements once a week three consecutive weeks in a legal newspaper published in or of general circulation within the city. The contract for such construction shall be awarded to the lowest responsible bidder.