The city council may, by four-fifths vote, deny all protests finding that the public health and safety require that the improvements be made and its decision thereon shall be final and conclusive. If any protests on matters which can not be modified as provided in Section 18690 hereof are sustained, the proceedings shall be abandoned but may be renewed at any time. No land shall be included within the district which in the judgment of the city council will not be benefited by the street lighting system as that body has finally determined to maintain and operate it.