If a sign built in nonconformance with this chapter as a result of a variance granted
by the chief building official or city council is blown or knocked down or a substantial
part of such sign is destroyed, damaged or taken down or removed for any purpose other
than maintenance operations or for changing the letters, symbols or other matter on
such sign, such sign shall not be reerected, reconstructed or rebuilt, except in full
conformance with this chapter, unless another variance is requested by the owner and
granted by the chief building official or the city council in conformance with this
chapter.
