Accelerated Freshwater Harbor Corrosion Study in the Duluth-Superior Harbor

The steel sheet piling in the Duluth-Superior Harbor is corroding at an accelerated rate compared to other Great Lakes fresh water harbors and ports. Based on observations of both older and new sheet pile installations, the accelerated corrosion appears to have begun in the late 1970s. Underwater inspections have revealed that the corrosion is widespread throughout the harbor on all types of steel piling buttressing the docks. Some of the steel beams supporting the dock structures have holes the size of footballs (15–30 cm) which have already been or are in the process of being repaired. To provide a systematic focus for the needed research and mitigation recommendations, a steering committee was formed and recommended the corrosion problem be reviewed by an independent group of experts, each specializing in a different area of corrosion. In September 2004, a panel of five experts in corrosion, microbiology, metallurgy and chemistry examined the corrosion problem. The experts narrowed down the initial list of 12 possible causes to a few likely causes and made both long- and short-term recommendations. This paper will 1) describe the accelerated fresh water corrosion observed in the Duluth-Superior harbor, 2) describe the project steering committees and expert panels role with the project, 3) discuss how project funding is being pursued, and 4) discuss the ongoing studies and preliminary results to determine the cause or causes of the accelerated freshwater harbor corrosion.