In message , Ian Jackson
writes

Telephone poles are routinely dug around and then treated with some
chemical preservative.

Not the old ones. I personally know poles that are at least 70 years
old, and as far as I know, have never been given any maintenance.

Open Reach parked in my yard a few weeks back to inspect a pole.

As far as I could see this involved digging down 6" round the post,
inspecting for rot and then treating with some chemical. I didn't stand
over him:-)

Look up Boron as a timber preservative.

Some years ago, I noticed what appeared to be large nails hammered
into timber electricity poles at ground level. The guy I asked said he
thought they were to extend the life of the pole.

I've never heard of that. Is it possible that something leaches out of
the nails if the wood is soaking up water (and therefore more likely to
rot)?

--
Tim Lamb