(a) Regulations not retroactive. The regulations prescribed by this article 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 the effective date of the ordinance from which this article
is derived, except as otherwise indicated, or otherwise interfere with the continuance
of any nonconforming use. Nothing herein contained 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 from which this article
is derived, and is diligently prosecuted.
(b) Marking and lighting. Notwithstanding the provision of subsection (a) of this section, the owner of any
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 city to indicate to operators of aircraft in the vicinity of the airstrip, the
presence of such airport hazards. Such markers and lights shall be installed, operated
and maintained at the expense of the city.
