Easiest way out of this situation is to use a 10 foot 5/8 inch ground rod, and drive it in as deep as possible for the 8 feet.
The physical protection would be necessary for the exposed piece if it was subject to physical damage.
Don: If you recall when we met in Chicago a while back, I took a picture of the rod driven in the gas station next door to the hotel below the service they upgraded to a 4 wire wye service and that rod was exposed about 6 inches and was not a 10 foot rod.
I once sent in a proposal to require the rod to be driven to 7 ft 9 inches to allow the end to be visible, and was shot down because the committee wanted me to provide a fact finding report!!
