Wow, just a small comment, you are or have a structual enginere as a friend?
Local governing body aproval, at that height your turbine will stick out like the preverbial dogs b.....s.
Are you planning this as a tilt tower? The logistics of tilting 120' boggles my mind, but with suficient determination you will suceed I'm sure. My observation of large towers ie. Jackob's 10Kw is that they used a lattice tower.
I am a believer in several smaller units, but then I don't need to go so high either.
Non of which answers your question of where to source 10' pipe.
allan down under