All presently maintained openings shall be guarded by a suitable cover or railing as approved by the director of public works. It is unlawful to construct any opening or stairway in any public street, sidewalk or alley. Exceptions to this section may be made only upon the written approval of the director of public works. Such permit shall not be issued if the opening or stairway interferes with pedestrian or vehicular traffic, public utilities, or results in a safety hazard. (2004 Code)