If you are bonding dirt, it has to be copper. If this is encased in concrete it can be the steel rebar or presumably after 2008, steel mesh.
I understand some people do not think a single #8 is sufficient but Florida decided in 2006-7 that this would work and adopted the 2008 rule early as an addendum.
(probably driven by the pool lobby)
I am not sure where any of this actually came from and what testing was done to prove the effectiveness but differences in soil material, moisture content and the surface itself would make this testing somewhat useless when any of those changed from the tested media.
