Ride down trail that parallels the train-tracks. (Trail length unknown - I haven't tried this one yet.)
"Take I-75 to Chastain Road (Exit 117). Turn left and follow all the way to Hwy. 41 (just past airport). Turn right on 41. Go north for about fifteen miles until you see a Emerson city sign. After you see that sign continue north until you cross a bridge over train tracks. Pull off to the right of the road immediately after the bridge.
http://www.singletracks.com/item.php?c=1&i=572