Within the districts established by this title or amendments that may later be adopted, there exist lots, structures, and uses of land and structures which were lawful before this title was passed or amended but which would be prohibited, regulated, or restricted under the terms of this title or future amendment. It is the intent of this title to permit these nonconformities to continue until they are removed, but not to encourage their survival. Such uses are declared by this title to be incompatible with permitted uses in the districts involved. It is further the intent of this title that nonconformities shall not be enlarged upon, expanded or extended, nor be used as grounds for adding other structures or uses prohibited elsewhere in the same district. A nonconforming use of a structure, a nonconforming use of land, or a nonconforming use of a structure and land shall not be extended or enlarged after the effective date hereof. (1997 Code § 12-251)