No trench shall be opened in any graded street or thoroughfare for the purpose of laying pipes or conduits more than six hundred feet in advance of pipe or conduit placed therein, except in cases of emergency or by consent of the Director of Public Works. All excavated material shall be piled along the trench leaving clear the area of at least one foot on each side thereof. The surface material shall be piled on one side of the trench and the subsoil on the other side of the trench. If a crossing street intersects the excavation, a driveway shall at all times be maintained. Also all private driveways shall be kept opened. (Ord. 4363-NS § 6, 1968)