Lots abutting residential districts. Unless authorized as a special use, no building or structure shall be erected, nor shall any outdoor processing equipment or operation, be located, closer than 100 feet to any residential district nor shall any parking area be closer than 40 feet to any residential district, which forty-foot area between such parking lot and such residential district shall be maintained as green area entirely covered by grass, shrubs, and/or trees. See off-street parking regulations elsewhere in this chapter.