Assessing the Role of Microorganisms in the Accelerated Corrosion of Port Transportation Infrastructure in the Duluth-Superior Harbor

The economies of coastal communities around the Great Lakes have historically been dependent upon maritime transportation. Urban ports and waterways continue to accommodate expanding trade, growth of tourism, and recreational boating. Even in this challenging economic period, planned expansions in the iron-ore, slab-steel, low-sulfur coal, and nonferrous metals industries and growing tourism indicate that the need for adequate port infrastructure will increase and become even more important to Minnesota’s economy over the next decade. Yet, Lake Superior harbors and the maritime industry are facing a serious problem: accelerated corrosive loss of port infrastructure. Steel sheetand H-pilings used for docks, bridges, and bulkheads have been reported to be corroding at an accelerated rate in the Duluth-Superior harbor. The increased rate of corrosion appears to have begun in the late 1970s, and will require expensive replacement of port facilities if the cause and possible remedies cannot be identified. Approximately 20 kilometers of steel sheet-pilings appear to be affected in the Duluth-Superior harbor, which may cost more than $200 million to replace. When Lake Superior water levels dropped in 2007, the extent of piling corrosion was clearly visible on numerous steel structures in the harbor. This article highlights the extent of corrosion of port transportation infrastructure in the Duluth-Superior harbor and describes the methodology and findings from our laboratory’s initial studies of the possible role of microorganisms in this corrosion. Our goal was to determine if differences in microbial communities between two corroding structures and a less-affected site indicated the participation of bacteria in this accelerated corrosion process. Our research group is continuing to actively investigate the cause of this problem through field and laboratory studies. Assessing the Role of Microorganisms in the Accelerated Corrosion of Port Transportation Infrastructure in the Duluth-Superior Harbor