CA Gov't Code Section 50485.10

Any airport zoning regulations shall provide that before any nonconforming structure or tree may be replaced, substantially altered or repaired, rebuilt, allowed to grow higher, or replanted, a permit must 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 establishment or creation of an airport hazard or permit a nonconforming structure or tree or nonconforming use to be made or become higher or become a greater hazard to air navigation than it was when the applicable regulation was adopted or than it is when the application for a permit is made. Except as provided herein, all applications for permits shall be granted. No such permit shall be required to make maintenance repairs to or to replace parts of existing structures which do not enlarge or increase the height of the existing structure.

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 this article, may apply to the administrative agency for a variance from the zoning regulations in question. Such variances 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 and this article; provided, that any variance may be allowed subject to any reasonable conditions that the administrative agency may deem necessary to effectuate the purpose of this article.

In granting any permit or variance under this section, the administrative agency may, if it deems such action advisable to effectuate the purposes of this article 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 city and county, at its own expense, to install, operate, and maintain thereon such markers and lights as may be necessary to indicate to flyers the presence of an airport hazard.