All contractors regulated under this chapter shall comply with this chapter and all ordinances relating to or regulating the activities engaged in and, in addition thereto, shall, at least once each week, remove or cause to be removed from the site of the contractor's activities all trash, refuse and waste materials. Contractors shall at all times keep the site of activities in an orderly condition, free from standing water, unguarded dangerous implements and health and safety hazards. Contractors shall not obstruct traffic on streets or sidewalks or permit dirt or waste materials to fall or be carried onto or remain on such public ways.