Whenever any person or corporation shall, under authority of this chapter or otherwise, place any obstruction in any street or alley or make any excavation therein for any purpose whatsoever, it shall be the duty of such person or corporation to keep such obstruction or excavation properly safeguarded by substantial barricades and to display lighted red lanterns or other lights or flares from dusk until daylight in conformity with such regulations as may be specified by the City Engineer. Whenever, in the opinion of the City Engineer, the public safety is so seriously endangered by said cuts or excavations as to require constant supervision from dusk to daylight to insure that all barricades are in proper condition, that all warning lights are burning, and that traffic is properly routed around such barricades, the person to whom the permit for the work has been granted shall be responsible for furnishing a night watchman for that purpose. (Ord. 1700 § 8, amended, 1971)