I will assume that you know that one rod equals 16.5 feet.
I, personally, do not know of any “going rates” for a 20" gas line ROW in Carter County or for any size gas line in that county or any other county. But, having a work history of being a pipeline ROW agent (Permitting Specialist) I do know that everything is negotiable.
Nothing is “set in stone.” You might want to navigate on to the Carter County Group section (see listing above) and ask around if you are having trouble making up your mind.
Negotiate.
Good luck,
Pat