I am running a 70A service to my sheds this weekend. I did some "prep" work this past weekend by removing a length of unused UF cable that spans across part of the yard where my subpanel conduit will cross. The cable looked like it went straight to my well and since the outlet box there had two conduits going to it I figured one was the service and the other was my mysterious unused cable so I started digging up from there. I later discovered to my horror that the cable I was following was the service for the well, and it was only buried maybe 5" into the ground. Furthermore, as I was following it I got a healthy dose of electricity sent through my body where some of the sheathing had been cut. Even further, this cable has white sheathing, which leads me to believe it is not UF but NM (I did not uncover enough of it before getting shocked to read the writing on it to identify it).
The power for the well comes out the backside of the house into a metal single gang box and then down a small section of metal conduit to the ground (and not even, about 1" is exposed). When I run my subpanel conduit, my trench will include the length from the back of the house to the well. Should I go ahead and run a new cable for the well considering it isn't buried nearly as deep as it should, the sheathing has damage, and it could possibly not even be UF cable? In terms of work it'd be an extra 20ft or so of trench for the branches off the main stretch to the house and well.
For the subpanel I will be running #4 AWG THWN wires. I took off the metal plate for the well service and it is only using a 2 conductor + ground wire. Is it best to run three #10 THWN wires (two conductors and from the NEC table I believe I also need a #10 ground) in its own conduit for the well or should I just run a 10-2 w/ ground UF cable? Also, I would be running schedule 40 PVC for the conduit, can I thread that into the metal conduit box or do I need to replace that too with a plastic box?