OLD HICKORY, Tenn. (May 15, 2013) – The U.S. Army Corps of Engineers at Old Hickory Lake is offering free guided public tours of the Old Hickory Lake’s Navigation Lock and Powerhouse 9 a.m. and 11 a.m. Saturday May 25, June 29, July 20, Aug. 10 and Aug. 25. The tours are approximately one hour in length.