When the doing or performing of any of the things mentioned in sections 12.16.010 through 12.16.340 of this division, in any of the streets of this city shall unreasonably interfere with travel thereon and the engineer so finds, he shall notify the permittee to that effect, and thereafter such work shall be prosecuted diligently for a total period of not less than fifteen (15) hours each calendar day from twelve o'clock (12:00) midnight to twelve o'clock (12:00) midnight, except holidays and Sunday. (Prior code § 74206)