All outdoor play areas shall be screened from adjacent properties by a fence or wall at least six feet in height and screen plantings within a 15-foot setback area along property lines. Outdoor areas located near or adjacent to hazardous areas determined by the Board to be unsafe, including but not limited to streets, roads, driveways, parking lots, railroad tracks, swimming pools, streams, steep grades, open pits, high-voltage lines, or propane gas tanks, shall be fenced or otherwise protected by a natural or man-made barrier.