1. (a) Permits. Where advisable to facilitate the enforcement of zoning regulations adopted pursuant to section 15-91, a system may be established for granting permits to establish or construct new structures and other uses. Before any nonconforming structure or tree may be replaced, substantially altered or repaired, rebuilt, allowed to grow higher or replanted, a permit shall be secured from the administrative agency authorized to administer and enforce the regulations, authorizing such replacement, change or repair. No permit shall be granted that would allow the structure or tree in question to be made higher or become a greater hazard to air navigation than it was when the applicable regulation was adopted; and whenever the administrative agency determines that a nonconforming structure or tree has been abandoned or more than eighty per cent torn down, destroyed, deteriorated or decayed:

   1. (1) No permit shall be granted that would allow such structure or tree to exceed the applicable height limit or otherwise deviate from the zoning regulations, but a permit shall be issued as of right if the structure as erected or altered is in conformance with the regulations or will not constitute a greater hazard than the structure that is replaced or altered; and (2) whether application is made for a permit under this section or not, such agency may by appropriate action compel the owner of the nonconforming structure or tree to lower, remove, reconstruct or equip such object as may be necessary to conform to the regulations. Except as indicated, all applications for permits for replacement, change or repair of nonconforming uses shall be granted.
2. (b) Variances. Any person desiring to erect any structure, or increase the height of any structure, or permit the growth of any tree, or otherwise use his property, in violation of airport zoning regulations adopted under section 15-91, may apply to the board of appeals, as provided herein, for a variance from the zoning regulations in question. Such variance shall be allowed where a literal application or enforcement of the regulations would result in practical difficulty or unnecessary hardship and the relief granted would not be contrary to the public interest but do substantial justice and be in accordance with the spirit of the regulations.
3. (c) Obstruction marking and lighting. In granting any permit or variance under this section the administrative agency or board of appeals may, if it deems such action advisable to effectuate the purposes of sections 15-88 to 15-97, inclusive, and reasonable in the circumstances, so condition such permit or variance as to require the owner of the structure or tree in question to permit the municipality, at its own expense, to install, operate and maintain suitable obstruction markers and obstruction lights thereon.

(1953, S. 2418d.)