A. The regulations prescribed by this chapter shall not be construed to require the removal, lowering, or other changes or alteration of any structure or tree not conforming to the regulations as of the effective date of this chapter, or otherwise interfere with the continuance of any nonconforming use. Nothing contained in this chapter shall require any change in the construction, alteration, or intended use of any structure, the construction or alteration of which was begun prior to the effective date of the ordinance codified in this chapter, and is diligently prosecuted.

B. Notwithstanding the provision of subsection A, the owner of any nonconforming structure or tree is required to permit the installation, operation, and maintenance thereon of such markers and lights as shall be deemed necessary by the city manager to indicate to the operators of aircraft in the vicinity of the airport, the presence of such airport hazards. Such markers and lights shall be installed, operated, and maintained at the expense of the city. (Ord. 1022 § 6, 1974).