Blimey, where do they get that from? 1km away, 15m is insignificant. The Inner Horizontal Surface which is fairly close in, is 150m AAL and approach slopes/take off climb surfaces will soon be above 15m.
Believe or not, there is no law to prevent a crane operator erecting a crane just outside an airfield. There is a British Standard which says, something along the lines of, if you intend to erect a crane above the surrounding buildings and trees within (I think) 7km of an airfield you should consult with that airfield, but I have come across crane operators who have never heard of it!! All you can do is threaten them with Article 73 (Endangerment).
MAN777, just speak with the airfield.