I wanted to come back to followup on my thread. With cooler weather and two other trench projects lined up, I rented a trencher last weekend and finally buried the power line to my barn. Here are a couple pics:
The trencher had no problems cutting a nice trench 4" wide and 24" deep, although I had to fight large tree roots in 4-5 spots. Despite the trencher doing the hard work digging the trench, filling it back in by hand was still a major chore due to a combination of the long trench, heavy brush, and tons of roots in the top soil layer that I had to push the dirt through to get it back into the trench. Even though I didn't have to dig the trench, I was still whipped doing everything else.
About 2/3 of the distance, the sub soil was sandy and fairly easy to work with. The other 1/3 was heavy clay and tough. I had a helper for the sandy part -- at lunch, I mentioned that it was like a beach out there with all the sand, and don't you just know that kid was out there lickety split with her shovel.
I had some scraps of PEX piping, so I put that down in the trench too, buried about 6" above the power line. No use for it now, but if I ever need to run water out towards the middle of our yard, or near our barn, or for animals, the hard work will be done.
After getting that trench done, I also cut a french drain in our backyard and trenched to bury some drain tile for the gutters on the barn. Definitely got my money's worth out of the trencher rental.
BTW, in retrospect, I would still strongly consider running above ground conduit instead of trenching. Trenching out in the open is not too hard, but going through the woods like this makes the job a lot harder all the way around. I prefer to have the power line buried for protection, but if I was forced to do this job all over again I'd probably give above-ground conduit strong consideration.