The toxic contaminants in the sediment under Minnesota Slip on Duluth's waterfront will be capped and contained in place, not removed from the harbor.
The Minnesota Pollution Control Agency on Monday announced its final plan to deal with the huge amount of nasty chemicals in the muck at the bottom of the slip that's home to the William A. Irvin ore boat and part of Duluth's charter fishing fleet.
There's a total of 37,000 cubic yards of sediment in the slip, but most will be capped without being moved. About 2,500 cubic yards of contaminated sediments in shallow areas of the slip will be relocated in deeper water. All of the contaminated sediment will then be capped with three feet of sand or similar material so the chemicals can't mix into the water and fish in the harbor.
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The slip will be about 12 feet deep throughout when the project is completed, said Heidi Bauman, project manager for the PCA, so both the Irvin and fishing boats can continue to call it home.
The PCA says the $1.6 million project was the least expensive of several options considered, except for doing nothing. The cost to remove all of the contaminated sediment was estimated at $6.5 million.
The slip's contamination is the result of a century of industrial and shipping activities on the harborfront and includes PAHs, mercury, chromium, lead, zinc, PCBs and more.
Work could begin in 2018 if funding is available. In addition to waiting for funding, the PCA is waiting for the Irvin to be moved, repaired and returned to the site before the capping work is done.
The agency said capping the material, as was done with some of the contaminated areas of Striker Bay in Duluth, met all of the goals of the project, including reducing any exposure of the contaminates to the ecosystem but also leaving the slip deep enough for recreational boats to use.
The PCA is working with the U.S. Environmental Protection Agency and U.S. Army Corps of Engineers to design the project, a step that includes additional environmental review and public comment options.
Federal Great Lakes Restoration Initiative money already is available for the project, but state funding for the cleanup is dependent upon the state Legislature passing a state construction/bonding bill, which contains money for this and other St. Louis River Area of Concern cleanup projects.
The slip is one of 10 spots on Minnesota's side of the St. Louis River that are slated for cleanup in coming years.
