Whenever any person or persons, corporation or corporations shall have authority under any contract with the said City or any officer thereof, that may permit the authorizing of same, to tear up, excavate, remove or replace any of the sidewalks, curbs or gutters in said City so as to obstruct and prevent the same from being used for the time being for the purpose of travel, such person or persons shall place or cause to be placed in conspicuous positions where such work is being done, at twilight in the evening, suitable and sufficient lights and keep them burning through the night during the performance of such work and the continuance of such obstruction. Any obstruction necessary for the performance of said work shall be removed as soon as the job is completed, and the work shall be finished as expeditiously as possible.