When workers slide Duluth’s cargo ship museum, the 610-foot William A. Irvin, out of its 30-year mooring place for a while later this year, they’ll have to move carefully.

Very carefully.

Environmental cleanup workers need the retired ore boat moved out of the way by Oct. 1 so they can reach the sediment underneath as part of a larger effort to remediate industrial pollution in the Duluth harbor. Problem is, there’s only a 15-inch clearance between the width of the ship and the opening in the blue pedestrian Minnesota Slip drawbridge blocking its way.

“It’s a very, very tight fit,” said Roger Reinert, board president of the Duluth Entertainment Convention Center (DECC), which owns the ship. “That makes us nervous.”

Shipping officials have assured the DECC board and the city that they can do the job without damage to the boat or the bridge with careful monitoring of waves and wind.

So while the floating museum needs to be moved anyway — at a price of up to $600,000 — the DECC board is considering where the ship should go next.

It could be moored along the sea wall in the harbor, with the hopes of opening it up for the busiest part of the coming tourist season, including the popular Haunted Ship tours in October. That would involve building temporary infrastructure such as landing equipment and water and electricity at a cost of up to $100,000.

“That’s no small change so we need to think it through,” Reinert said, adding that officials are studying the cost benefit of such a move. The temporary spot would also expose the ship more to the weather, he noted.

Another option is to get the ship towed straight to a shipyard and have it dry-docked and repainted, an approximately $350,000 project that will have to be done at some point.

“In my opinion, we’re only doing this once,” Reinert said. “If [the Irvin] comes out for the Minnesota Slip project, let’s get it done.”

The ship is not open now, while the city-owned sea wall in front of it is being reconstructed.

The ship needs to be moved so that workers can level the sediment in the slip, which is laden with industrial waste from before the 1970s, then cap the sediment by covering it with a couple of feet of clean sand and then a layer of small rocks. It’s a $1.9 million project, with federal money paying 65 percent of the cost, said Heidi Bauman of the Minnesota Pollution Control Agency.

The slip isn’t big enough to move the Irvin within it to get the work done, Bauman said.

As the flagship vessel of U.S. Steel’s Great Lakes fleet, the Irvin was launched in 1937 and “provided comfort and elegance to dignitaries and guests who traveled the Lakes,” according to the DECC. The boat ran for more than 40 years.

It became a tourist draw in 1986, originally docked behind the convention center. But after a storm that year, it was moved to the slip, where smaller boats are also docked behind it.

An average of 36,000 people tour the ship each year from May through September. The Haunted Ship tours in October bring in more than 20,000 people a year.

There’s a synergy between all the projects in the prominent area of Duluth, said Jim Filby Williams, the city’s director of Public Administration.

The ship needs to be moved for maintenance and repainting of its hull soon, anyway, he said, so it makes sense to take advantage of the cleanup timing.

“It absolutely has to come out ... in the next few years anyway in order to preserve it,” Filby Williams said.

The working plan would have the maintenance on the Irvin done in the winter and spring, with the ship moving back into the slip in time for the next tourist season.