Thanks for the replies. I answered my own question, however. I found some of the original design drawings. The "extra" ground wires go from a lineup of 12KV switchgear, which is the service for the facility, to wall mounted ground bus' in each unit substation room. This is a typical ground bus where all the local bonds and transformer grounds are connected. I suppose the original designers meant to keep all the different buildings at the same potential. I know of two that aren't though because the original contractor never connected them!
The small pull lines were left by the original contractor. The 1/4" line we installed in preparation to pull the 12KV feeder for one of the two 12KV subs we are adding here. We pulled it Friday night (all 1140 feet!). but our drawings did not call for the extra ground that the original design called for.
Hmm. This brings up a question. Although this conductor is not required in the NEC, what possible benefits or problems could it bring to the facility?
