1020.11   SAFETY REQUIREMENTS.
   (a)   Safeguards.  All openings, excavations and obstructions shall be properly and substantially barricaded and railed off, and at night shall be provided with approved warning lights. Warning lights perpendicular to the flow of traffic shall not be more than three feet apart, and parallel to the flow of traffic not over fifteen feet apart.
(1981 Code § 4.31)
   (b)   Shoring Excavations.  All openings and excavations shall be properly and substantially sheeted and braced as a safeguard to workmen and to prevent cave-ins or washouts which would tend to injure the thoroughfare or sub-surface structure of the street.
(1981 Code § 4.32)