All trenches in public streets and alleys shall be properly protected at night with substantial barricades at least three feet (3') high, same to have contractor's name and telephone number printed thereon, and red lights shall be placed at each end of the trench, in cases where the trench is ten feet (10') or more in length, or an obstruction, and same shall be kept brightly burning from sunset until sunrise. The chief of the fire department shall be notified of such obstruction prior to dark of same day that it is put in. The plumbing inspector shall prescribe such rules and conditions to be followed and performed as may be necessary for the safety of the street, alley, sidewalk or sewer through which a permit may be issued to excavate or connect. (1983 Code § 5-306)