The Interlake Steamship Company and Interlake Transportation have received 7,200 hp Z-drive tug Dorothy Ann. Designed by Ocean Tug & Barge Engineering, the 124.5 ft. long Dorothy Ann was constructed in 1998 by Bay Shipbuilding Company. Final outfitting was performed by Bark River Towing, Weld All and Marine Accommodations. Dorothy Ann is the largest Z-drive tug built to date in North America. Twin Ulstein Z-drives enable the vessel to turn on her own axis, stop within her own length and move easily in any direction. Coupled with self-unloading barge Pathfinder, the pair is the most maneuverable unit on the Great Lakes, says the company. Alone, Dorothy Ann can travel at 16 mph; when pushing the loaded barge, open lake speed is 11.5 mph.