D.C. Mun. Regs. tit. 24, r. 24-2002
Each highway, street, sidewalk, or alley opening or cut, open manhole, or open conduit shall be guarded securely; and a red flag or other danger signal, including red lights when necessary at night, shall be displayed close to the opening at all times.
Each open manhole, coal chute, vault cover, or any open sidewalk or alley space used by or under the control of the owner, tenant, or occupant of property abutting on the opening, shall be guarded securely; and a red flag or other danger signal shall be displayed or employed close to the opening by the owner, tenant, or occupant, at all times.
Every broken manhole cover, vault, or other cover to an underground sidewalk or alley space, including Hyatt lights, used or under the control of the owner, tenant, or occupant of property abutting on the cover shall be guarded securely to ensure public safety; and a red flag or other danger signal, including red lights at night when necessary, shall be displayed on or close to the defective covering by the owner, tenant, or occupant.
No grate, door, or other opening in any highway, sidewalk, or alley in the District shall be permitted to remain open any longer than may be reasonably necessary to enable the owner or occupant of abutting property to move or remove goods in the course of his or her trade or business.
D.C. Mun. Regs. tit. 24, r. 24-2002