(MN) Minnesota Public Radio – A new study of rusting steel supports in the Duluth-Superior harbor points to dissolved copper in the water as a contributing factor.
Duluth shipping officials raised the alarm a few years ago about accelerating corrosion eating away an estimated 50,000 of tons of steel a year. Steel supports several miles of harbor walls and shipping docks.
The study cites a combination of factors including bacteria, dissolved copper and scouring by ice. Jim Sharrow, with the Duluth Port Authority, said the damage has been evident where ice forms. More