According to RBM rbm2(remove :
If you don't run the ground with the feed conductors, you have to meet
certain conditions like nothing conductive and grounded can be installed
between the two buildings. At least where direct burial cable is concerned,
you get one little nick in it and it disintegrates

Which is what John was proposing - ground conductor with feed (4 wire) and
grounding electrodes at _both_ ends. Ground loop. The electrodes themselves
will disintegrate.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.