[TowerTalk] how much rust is too much?

[Matthew Kaufman]

I've just acquired a property with a 150 foot tower, appears to be Rohn 
45, guyed at 5 levels. It was installed in the early 1970s(!).

Prior to climbing the tower, I want to be sure it is safe. I've 
excavated along the guy anchors down to concrete, and they appear a 
little "crusty" but not more rusted than that. Still need to check the 
very edge where they meet the concrete close-up to see if it is any 
worse there. Not sure if I should try removing the rust or just leave as-is.

The base of the tower is a pier-pin base on concrete with the tower 
bolted to the base plate. Some time over the past decades, dirt fell 
down a slope and covered the base plate and the bottom bit of tower 
(less on one leg than the other two). Near the surface I can just see 
that the galvanizing has worn through, but below that there is 
progressively more and more rust. The tower still feels solid, and I've 
been working on removing the rust to see how much material loss there is 
and it doesn't look *that* bad... but how do I know how much is too 
much? Can I measure the diameter of the leg after removing the rust and 
compare to the non-rusted portions of the tower?

As far as removing the rust, I got some of the thin areas cleared with a 
chelating rust remover gel, and the rust on the base plate cleared with 
a stripper wheel on an angle grinder, but I'm thinking a small 
sandblaster might be the best for the legs themselves?

Picture of the base immediately after uncovering it, before removing any 
dirt or loose rust: http://www.matthew.at/tower-base.JPG

Picture of one of the three guy anchors: 
http://www.matthew.at/guy-anchor.JPG

Any and all suggestions welcome.. obviously I'd like to salvage as much 
of the current install as possible, but I don't want it killing anyone 
either.

Matthew Kaufman, KA6SQG
matthew at matthew.at (mailing lists)
matthew at eeph.com (personal)
http://www.matthew.at