The permit holder shall erect and maintain suitable barriers to confine earth and excavation materials from spilling or falling upon highways and sidewalks as little as possible. He shall construct and maintain adequate and safe crossings over excavations and across highways under improvement to accommodate vehicular and pedestrian traffic at all times, as required by his permit. If required by his permit, or if required by the superintendent of public works, he shall erect such fence, railing, or barriers about the site of the excavation work as shall prevent danger to persons using the city street, sidewalk, alley or other public ground, and such protective barriers shall be maintained until the work shall be completed or the danger removed. At twilight there shall be placed upon such place of excavation and upon any excavated materials or structures or other obstructions to streets, alleys, sidewalks, and other public grounds, suitable and sufficient lights which shall be kept burning throughout the night during the maintenance of such obstructions. It shall be unlawful for anyone to remove or tear down the fence or railing or other protection barriers or any lights provided therefor for the protection of the public. (Ord. 280 § 4, 1969)