[TowerTalk] how much rust is too much?

[Donald Chester]

It doesn't look too bad from the photos. Surface rust is to be expected. I would carefully inspect the base to see if most of the steel is still there.  The guy anchor looks OK as well, but I would inspect it right where it goes into the concrete. Look for any signs of corrosion or cracks in the steel. I dug up one of mine a couple of years ago after a mower  hit the anchor, and the surface of the rod looked about the same as what I see in your photo. I actually got down and looked at it with a strong light and magnifying glass just to make sure. No apparent damage from the mower, so I re-filled the dirt.

What looks worrisome with yours is that it appears the base pier is below grade, and the rest was back filled with dirt. I can't understand why whoever constructed the tower didn't raise the base pier a few inches above the ground just to make sure none of the steel would come in contact with the ground.  Perhaps someone added topsoil to the area after the tower was built. If the integrity of the structure still looks good after careful inspection, I'd  clean everything off really well, and paint over the rusty metal with oil base aluminium paint or cold-galv.  I've found the aluminium paint to hold up longer than cold-galv in the spray can, but the brush-on stuff might be better.

Then I'd dig a drainage ditch and remove the top soil down below the level of the concrete for a radius of several feet round the base of the tower, assuming the ground slopes downwards in at least one direction. Otherwise, you will need a sump pump to keep the base dry, if you can't find some way to keep the water flowing away naturally.

One thing. DON'T even think about back filling the hole with concrete to get it back up to grade. The base pin and  plate is a far better way to do it than the typical Hammy Hambone method of burying the bottom section of tower in the concrete.  You want the tower to be able to sway and give a little under high wind conditions. Fixing the base solidly in the pier buried under concrete causes movement of the tower under wind conditions to put all the stress on the tower sections, possibly causing failure at the welds under extreme conditions. Besides, back filling with concrete would be  no guarantee of a perfect seal between the old and new concrete, and any additional rust would then be hidden from view - not good.

Don k4kyv