[ArthurDent]

Well, figured you'd get some knowledgeable input by now, but this will serve as a bump. While not an electrician given your geographical location safe rather than sorry might be the way to go. Worst case sink a temp ground rod, & run a jumper before you cut the existing. Then just delete the temp work when you get the new location set & reconnected.

Good to hear the innovative construction techniques didn't result in any issues. 

[thunderbrick]

I like that idea!     I can punch a hole farther away and run a temp jumper before cutting the original.  I've got plenty of 12-2 wire around that'll do the job. 

Or I can pull all the slack into the house and just bolt the 2x12 beam right on top of the wire.