"Jim Miller" wrote
As you noted I wouldn't dream of modifying the electrical ground system
of the mains of the house. I'm only going to put a little parade of
ground rods on the path to the mains ground rod and daisy chain them
all together with #2 with a pair of clamps on each rod. It will only
take two additional rods to get around the corner and up to the service
ground. I'll have to dig down to get to it I suppose.

You should be good to go Jim. You might not have to scratch far to find the
AC mains grounding electrode. Depending on when your house was built, it
could even be a cold water pipe ground. If it is a rod, it is probably not
buried deep at all. The 10' rule is recent and not followed in most
residential cases anyway. When a local inspector arrives to approve a
contractor's installation, he is checking only for a 25ohm or less grounding
electrode. If the contractor cannot achieve 25 ohms or less from one
electrode, the code requires he sink a second electrode. And nothing else.
That's irony, huh?

Best regards,

Jack