Portland poured concrete sidewalks shall be installed in all new subdivisions and around parks, schools and shopping areas. Sidewalks shall be at least four feet (4') wide. All sidewalks shall be constructed of concrete four inches (4") thick and five and one-half inches (51/2") in thickness where sidewalk crosses driveways. A sand or gravel base at least two inches (2") thick may be required. (1995 Code § 5.404)