SAULT STE. MARIE, Mich. (AP) -- The U.S. Army Corps of Engineers announced the seasonal closing of the Soo Locks in the Upper Peninsula city of Sault Ste. Marie a few days later than normal.
The Corps said Friday the Poe Lock stayed open three days past the traditional closing date of the navigation season at the shipping industry's request. The extension allowed for the movement of more than 400,000 tons of additional cargo.
The season's final vessel, the 639-foot Saginaw, cleared the lock Thursday. The adjacent MacArthur lock closed last month.
The locks, which are scheduled to reopen March 25, raise and lower ships hauling iron ore and other freight on the St. Mary's River between lakes Superior and Huron. More than 4,500 ships and about 80 million tons of cargo go through the locks each year.
About 4,000 cargo vessels passed through the locks during the 2011 navigation season, carrying almost 75 million tons of freight, the Corps said.
Duluth Seaway Port Authority Facilities Manager Jim Sharrow told Minnesota Public Radio News earlier this week that tonnage shipped through the port was down this season. The last vessel pulled into the Duluth port on Wednesday.
The Detroit District of the Corps of Engineers maintains a navigation system of 95 harbors, including the Great Lakes Connecting Channels that join lakes Superior, Michigan, Huron and Erie.