If any non-conforming use or structure is destroyed by any means,
including flood, it shall not be reconstructed if the cost is more
than fifty percent (50%) of the market value of the structure before
the damage occurred unless reconstructed in conformity with the provisions
of this Chapter. This limitation does not include the cost of any
alteration to comply with existing State or local health, sanitary,
building or safety codes or regulations or the cost of any alteration
of a structure listed on the National Register of Historic Places
or a State inventory of historic places.