Sault Ste. Marie, MI — The Soo Locks in Sault Ste. Marie are shutting down to marine traffic to allow the U.S. Army Corps of Engineers to perform maintenance. The Army Corps of Engineers says the locks on the St. Marys River between Lake Superior and Lake Huron are expected to be closed from Saturday to March 25. The complex consists of several locks that raise and lower vessels between Superior and Huron. Winter months are used for maintenance each year. Work this winter is expected to include hydraulic steel structure inspections and preventive maintenance on electrical and mechanical systems. More than 4,500 vessels, carrying up to 80 million tons of cargo, use the locks each year.