A structure which was lawful before the adoption of this Part, but which is not in conformity with the provisions of this Part, shall be subject to the following conditions (to be enforced by the appropriate authority as to class I and class II projects, respectively, under Part 871 of this Title:
(a) A nonconforming structure in the floodway may not be expanded, except that it may be modified, altered or repaired to incorporate flood-proofing measures, provided such measures do not raise the level of the 100-year flood.(b) A nonconforming structure in the floodway which is destroyed or damaged by any means, including a flood, to the extent of 50 percent or more of its market value at that time, may not be restored, repaired, reconstructed or improved except in conformity with the provisions of this Part.N.Y. Comp. Codes R. & Regs. Tit. 21 § 874.2