Preparations are already in the works for the delicate movement of the William A. Irvin, Duluth's 611-foot long floating museum.
For the first time in about 30 years, the retired laker will leave its berth in Minnesota Slip, squeezing through the abutments of the pedestrian lift bridge with just over 7 inches to spare on either side. The ship has never before passed through the bridge, which was built after the vessel was moored and placed on display in the slip.
Inch by inch, the Irvin will be guided meticulously via winch cables attached to both its bow and stern. As detailed in bid specifications, the ship's speed as it navigates the slip will be restricted to a maximum crawl of 1 foot every 4 seconds. At that rate, it will take more than 40 minutes for the vessel to move one length.
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"There will always be two winches on - one that pulls and one that brakes," said Chad Scott, a principal partner of AMI Consulting Engineers P.A.
He explained that controlling the speed of the ship is essential.
"When you take a large mass, if you get moving too fast you need a huge force to stop it," Scott said. "It's simple physics."
He estimates it will take about four to five hours to get the ship into open water.
"It's an orchestra that will be moving this vessel around and taking its time. It's not going to be a rush project," Scott said.
Jim Filby Williams, Duluth's director of public administration, said the movement of the Irvin is one of three linked projects, with the other two being the reconstruction of the seawalls at Minnesota Slip, and the remediation of contaminated sediments that have accumulated in the waterway.
The city of Duluth expects to spend a grand sum of about $800,000 from tourism tax collections to remove the Irvin from the slip, transport it to Fraser Shipyards in Superior, where it will be placed in drydock and then repainted, before it returns to Duluth in the spring.
But the city's costs pale in comparison to the $10 million that will be spent to complete the rest of the work at Minnesota Slip, with that larger burden being borne by the state of Minnesota, the federal Environmental Protection Agency and the Duluth Entertainment Convention Center.
The Irvin needs to be out of Minnesota Slip by Oct. 1 to allow for contaminated sediments there to be capped in place and stabilized. Filby Williams expects the vessel to be moved by late August or early September.
The timing will depend largely on the weather. The ship won't move in winds exceeding 5 mph or if gusts approach 10 mph. The contract limits wave heights to no more than 6 inches and currents to less than 0.5 feet per second.
Filby Williams said the ship likely will be moved during pre-dawn hours, when winds are typically more subdued and marine traffic is minimal.
"The narrow nature of the channel opening is what's adding a critical difficulty to the project. If it was 10 feet wider, I guess it would be a no-brainer," Scott said.
"You can't get the vessel turned at all or you're going to have problems," he explained.
Scott said the repair of failing seawalls was a necessary precursor, as its steel pilings had bowed so badly the Irvin would not have had room to safely clear the channel.
But the new seawall is straight and true. Scott said plans call for that wall to serve as a guide for the ship, with fenders placed along its length to prevent any direct contact. A couple of protection piles also will be installed to keep the vessel from drifting into the bridge abutments.
Scott said the Irvin will need to remain on a straight path even as it exits the slip to avoid contact with the bridge and the seawalls.
"We need a straight line, something that we can follow so that the vessel doesn't get turned. And it can't get turned by much or you're going to have issues," he said.
Wren Works LLC, the firm that will be hired to oversee the move, plans to use spud barges - which can be moored in place with through-deck pilings or steel shafts to provide a stable, solid platform - with fenders attached to guide the Irvin out into the harbor for about 450 feet from the bridge. A surveyor will be on hand to ensure the barges are properly aligned and secured in place.
The Irvin will undergo about $170,000 in improvements in preparation for the move, receiving work on its deck winches, anchor system, ballast alarms and rudder.
While relocating the Irvin will be costly, Filby Williams also views the project as an opportunity.
"Having to remove the Irvin in some ways is an unwelcome challenge, but there's actually something fortuitous about it, because the Irvin hasn't received substantial maintenance on its hull for 30 years, and in some places the pitting in the hull has eliminated nearly half of the thickness. We, as a community, were going to have to do this in 5-10 years anyway. But by doing it now, we're doing it with a level of expertise and support available that we probably would not have had if we were doing this only for the purpose of restoring the vessel," he said.
The city has submitted a Minnesota Legacy Grant proposal on behalf of the DECC, seeking $600,000 to $750,000 to cover the cost of work to be done at Fraser.
Filby Williams expects to learn by late October if that grant application was successful and said he's "cautiously optimistic" it will be.