(A)   Regulations not retroactive.  The regulations prescribed in this chapter shall not be construed to require the removal, lowering or other change or alteration of any structure or tree not conforming to the regulations as of November 9, 2004 or otherwise interfere with the continuance of a nonconforming use. Nothing contained herein shall require any change in the construction, alteration or intended use of any structure, the construction or alteration of which was begun prior to November 9, 2004, and is diligently prosecuted.
   (B)   Marking and lighting.  Notwithstanding the preceding provision of this section, the owner of any existing nonconforming structure or tree is hereby required to permit the installation, operation and maintenance thereon of such markers and lights as shall be deemed necessary by the Zoning Administrator to indicate to the operators of aircraft in the vicinity of the airport the presence of such airport obstruction.  Such markers and lights shall be installed, operated and maintained at the expense of the city.
(`93 Code, § 12-706)  (Ord. passed 10-21-74; Am. Ord. 1447, passed 11-9-04)