SAULT STE. MARIE, Mich. (WXYZ) — The Soo Locks closed earlier this month for the regular winter period, and the U.S. Army Corps of Engineers – Detroit District, has now posted photos showing what it looks like to dewater the locks.
The photos posted on the Facebook page show the dewatering process of the Poe Lock, the largest lock at the Soo at 1,200 feet long, 110 feet wide and 32 feet deep. It's the lock that the 1,000-foot freighters go in.
The first step, according to the U.S. Army Corps of engineers, is a crane lowering a panel bridge into place across the lock. Those bridges allow for heavy equipment to be moved when needed.
Next, a crane and barge move to one end to set up stop logs. Weighing 93,900 pounds each, there are eight logs stacked to create what they say is a "temporary dam" at the upper end. It holds back water from Lake Superior.
After the stop logs are put into place, the U.S. Army Corps of Engineers works to close guard gates at the lower end, creating another temporary dam. A tug pulls the gate into place. After it's closed, the pumps begin removing water inside the lock.
The U.S. Army Corps of Engineers then sends a diver into the lock.
"Divers play an important role in dewatering the lock, opening valves, ensuring the landing area for stop logs and the guard gates are clear of rubble and sealing leaks," they said on Facebook.
After about 18 hours, the Poe Lock is nearly empty, according to the Corps, but crews aren't done yet.
Next, they begin working on "lay-up" tasks, which prepare the lock for the work that will be done all winter. Crews start on the upper forebay, as it is the first area clear of water.
They also remove several manhole covers at the bottom of the lock to fully clear the area of water. Those manhole covers have steel straps securing them so they do not come up while in use.
In just about a day, the entire lock is dry.
Check out the photos below.