– The largest Great Lakes shipping project in recent history is now underway.

A new lock is being built at the eastern edge of Lake Superior to shore up a vulnerable link in the nation’s iron supply.

The $922 million passage at Sault Ste. Marie, Mich., would be large enough to handle the 1,000-foot lakers that carry taconite from Minnesota and Michigan to steelmakers along the lower lakes.

Today there is only one lock, the 50-year-old Poe, that can accommodate those ships, and it has been requiring increased maintenance. The U.S. Army Corps of Engineers, which owns and operates the Soo Locks, calls the Poe the “single point of failure in our nation’s iron ore supply chain” as about 85% of all tonnage that passes through must traverse the Poe Lock.

Equipment began to arrive last week to deepen the upstream channel above the decommissioned Davis and Sabin Locks, which will be replaced. That work will wrap up by November 2021. The new lock chamber is still being designed and could take until 2030 to open.

“It’s incredible that we’re starting this construction a year earlier than even the most optimistic projections when the project was re­authorized in 2018,” Lt. Col. Gregory Turner of the Army Corps of Engineers said in a statement. “Getting the first phase started sets the conditions for the project’s ultimate completion.”

The lock could open as early as 2027 if funding keeps flowing on time; it has secured 25% of its price tag so far. Late last year $75 million in federal money was set aside for the project.

The new, as-yet-unnamed lock would mirror the Poe at 1,200 feet long, 110 feet wide and 32 feet deep.

The Lake Carriers’ Association says the Soo Locks are responsible for $17.4 billion in economic activity every year. About 80 million tons of cargo pass through the locks annually.