This is from the FAA (
https://oeaaa.faa.gov/oeaaa/external/portal.jsp ).
CFR Title 14 Part 77.13 states that any person/organization who intends to sponsor any of the following construction or alterations must notify the Administrator of the FAA:
any construction or alteration exceeding 200 ft above ground level
any construction or alteration:
within 20,000 ft of a public use or military airport which exceeds a 100:1 surface from any point on the runway of each airport with at least one runway more than 3,200 ft
within 10,000 ft of a public use or military airport which exceeds a 50:1 surface from any point on the runway of each airport with its longest runway no more than 3,200 ft
within 5,000 ft of a public use heliport which exceeds a 25:1 surface
any highway, railroad or other traverse way whose prescribed adjusted height would exceed the above noted standards
when requested by the FAA
any construction or alteration located on a public use airport or heliport regardless of height or location.
The relevant regulation is 2004 CFR 14 Sec. 77.23, Standards for determining obstructions. The link is:
http://edocket.access.gpo.gov/cfr_20...14cfr77.23.pdf . The following FAA order about objects affecting the navigable airspace is also useful:
http://www.faa.gov/airports_airtraff...R/air0501.html . Figure 5-2-1 notes that a developer has to provide the FAA notice of proposed alteration or construction if the building or tower is more than 200 feet above ground level. The height of the ground level isn't at issue. Thus, if a developer built a 175 foot building on a mountain at 5,000feet above sea level, the developer not not be required to contact FAA.
Potential obstruction of the navigable airspace has been an issue in San Diego (
http://www.signonsandiego.com/uniont...n5tootall.html), Arlington, VA (
http://www.washingtonpost.com/wp-dyn...122702154.html ). and Miami (
http://www.redorbit.com/news/busines...flight_safety/ ).