Whenever a nonconforming use of land, premises, buildings or structures or any part or portion thereof has been discontinued for a period of 18 months, such nonconforming use shall not thereafter be reestablished on the said premises or the part or portion affected, and all future use of the said premises or part or portion affected shall be in conformity with the use permitted in the district in which it is located. Such discontinuance of the active and continuous operation of such nonconforming use or a part or portion thereof for such period of 18 months is hereby construed and considered to be an abandonment of such nonconforming use, regardless of any reservation of an intent not to abandon same or of an intent to resume active operations. If actual abandonment in fact is evidenced by the removal of buildings, structures, machinery, equipment or other evidences of such nonconforming use of the land and premises, the abandonment shall be construed and considered to be completed within a period of less than 18 months, and all rights to reestablish or continue such nonconforming use shall thereupon terminate.