All parking areas shall be effectively screened on any side which abuts or faces any premises situated in any residential zone by a fence, wall or hedge at least five feet in height, maintained in good condition, if required by the site plan approved by the Municipal Agency; provided, however, that such fence, wall or hedge requirement may be waived by the Municipal Agency if, because of topographical or other extraordinary or exceptional conditions, the same shall not be necessary to shield any abutting or facing premises situated in any residential zone.