[TowerTalk] Best way to dig holes

[Dick Green WC1M]

The time has come to dig holes for my 110' of Rohn 55. Mindful of the Rohn
specification to pour against undisturbed earth, and not wanting to get into
the business of building forms and backfilling, I  had planned to dig the
pier and anchor holes by hand. But time is running short before the snow
flies in New England. Also, I've switched from the 4a anchor spec to the 4d
anchor spec, which requires much larger holes: 3'x6'x4'.  I think I'm going
to need some machinery to get this job done without spending a huge number
of hours and what's left of my back.
 
Is it possible to dig anchor holes that size using a small excavator without
grossly overdoing it? Has anyone tried using a 1-man or 2-man gas auger to
do some of the digging, then finish by hand? I'm considering an auger to do
some of the excavation for the pier hole because I don't think even a small
excavator can do a 3'x'3'x'4 hole (actually, it only has to be
2.5'x2.5'x4'.) Also, I could use the auger to dig post holes for the tower
utility panel. Advice from the knowledgeable?
 
73, Dick WC1M