The U.S. Army Corps of Engineers, Detroit District, announces the seasonal closing of the Soo Locks in Sault Ste. Marie, Mich., from Jan. 15 through March 25. The Corps will use this time to perform critical maintenance on the lock structures. While closed to navigation, crews will be busy with a variety of maintenance projects on both the Poe and MacArthur Locks in preparation for another busy season. More than 4,500 vessels carrying up to 80 million tons of cargo maneuver through the locks annually. Iron ore, coal, wheat and limestone are among the most frequently carried commodities. Opened in 1969, the Poe Lock is 1,200 feet long. The MacArthur Lock was opened in 1943 and is 800 feet long.