ok, after putting on a #4 ground to the outside rods AND to the plumbing inside, my local city inspector says the wire has to be in conduit anywhere it's in close contact with concrete. I totally missed this in the code. Can someone cite this for me? The reason i went with the #4 is because the book said it didnt' need conduit for physical protection. I never saw any mention of concrete or electrolisys.
thanks