– Ever so carefully and before the eyes of an audience, workers slid the William A. Irvin museum ore ship back into its home in the Duluth Harbor on Wednesday evening, successfully maneuvering the 610-foot vessel through the opening of a pedestrian draw bridge with just 7 inches of clearance on either side.

Crews used tugboats, a line of barges, winches and other heavy equipment to guide the giant vessel into its mooring spot in the Minnesota Slip at a speed of what the project’s monitoring engineer estimated at 4 seconds per foot.

The conditions had to be just right: The boat has no working engine, rudder or ballast system, and it was not loaded with cargo, making its broad sides susceptible to winds. Workers stopped moving it periodically as it approached and floated through the narrow opening of the bridge, which was built after the ship was originally set up for tours in the Minnesota Slip near the Duluth Entertainment Convention Center.

A crowd of onlookers gathered by the slip to watch the feat. Cam and Lori Sandberg drove from their home in Eveleth, Minn., just to watch.

“We’ve both been fascinated by big ships,” Cam Sandberg said as he watched the hulking vessel slide through the narrow bridge opening. “It’s fascinating to watch the tight quarters.”

The Irvin had to be moved out of its home late last summer so workers could perform environmental remediation of the slip by capping industrial waste-laden sediment with clean sand and small rocks. Officials at the convention center, which owns the boat, decided to send the Irvin into dry dock for maintenance to repaint its hull. They found that corrosion was more extensive than expected, and more than 250 rivets were also replaced. Officials said a $504,000 grant from the Minnesota Historical Society would cover all the work’s costs.

The Irvin was once the flagship vessel of U.S. Steel’s Great Lakes fleet. Launched in 1937, it ran for more than 40 years.

It now hosts an average of 36,000 visitors on regular tours from May through September. In October, Haunted Ship tours bring in more than 20,000 people.

After forgoing two seasons without tours, officials said Wednesday they were happy to be bringing the vessel home.