All excavations, obstructions or unsafe conditions in or upon any street, alley, sidewalk or public place in the city shall be protected and guarded by sufficient barriers at all times and by red reflectors at night so as to warn passersby of such obstructions or dangerous place; and all such excavations, obstructions, and unsafe conditions shall be properly filled up, and the street, alley, sidewalk or public place restored to its former condition upon the completion of the purpose for which same was torn up, obstructed or rendered unsafe; and it shall be the duty of the person creating such excavation, obstruction, or unsafe condition, or causing the same to be created, to do and perform all the acts herein required to be done concerning the same, and it shall be the duty of the superintendent of streets to see that the provisions of this section are fully and faithfully observed. Said red reflectors herein referred to shall be of such size and make as the city engineer shall approve. (Prior code § 13.16.030.)