DETROIT — The Soo Locks in Sault Ste. Marie, Michigan, are closed to navigation until March 25, the U.S. Army Corps of Engineers, Detroit District, announced Wednesday.

The Corps will use this time to perform critical maintenance on the lock structures.

“The Soo Locks are critical to the Great Lakes Navigation System and we have a tremendous team that operates and maintains them throughout the year,” said Lt. Col. Greg Turner, district engineer, in a news release. “While we’ve begun work on building the new lock, it is as important as ever that we keep the existing infrastructure in good working order — this is our highest priority.”

With the annual closure, vessel traffic ceases through the Soo Locks for the season. While closed to navigation, both the MacArthur and Poe locks are dewatered and crews are busy with a variety of maintenance projects in preparation to reopen in March.

In addition to the MacArthur Lock undergoing a formal periodic inspection and routine minor maintenance, several key actions will be completed by the Soo Locks staff, including repairs to the empty/fill valve bulkhead slots, replacement of miter gate anchorage links for Gate 6, and replacement of the miter gate bevel gears on Gate 5.

For the Poe Lock, once dewatered, winter maintenance will include miter gate weld inspections/repairs on Gate 1, replacement of miter gate anchorage links for Gate 4, and minor repairs and re-stressing of miter gate diagonals on Gates 2 and 3.

The last vessel to traverse through the locks for the 2018-2019 shipping season was Motor Vessel Manitoulin. The ship was upbound from Sarnia, Ontario, bound for ESSAR Steel in Sault Ste. Marie, Ontario.

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.

The U.S. Army Corps of Engineers, Detroit District, maintains a navigation system of 95 harbors, including the Great Lakes Connecting Channels that join lakes Superior, Michigan, Huron, St. Clair and Erie.

For more information on the Soo Locks, visit lre.usace.army.mil.