Phase III GIS-based Sediment Quality Database for the St. Louis River Area of Concern (AOC)—Minnesota Focus - Overview of Sediment Quality Conditions in the St. Louis River AOC

The lower St. Louis River provides an important coastal resource to western Lake Superior. In particular, this transboundary waterway provides critical habitat to invertebrate, fish, and waterfowl species, and it also provides an economic venue for Great Lakes shipping and business in the Duluth-Superior Harbor. The lower estuary and harbor are bisected by the Minnesota-Wisconsin state line (Figure 1). Contaminated sediments have contributed to several use impairments in the lower St. Louis River and were a factor in the International Joint Commission's (IJC) decision to designate the lower St. Louis River as one of 43 Areas of Concern (AOCs) in the Great Lakes basin (IJC 1989). As such, contaminated sediments are an important nonpoint source of pollution to the St. Louis River AOC, especially in the Duluth-Superior Harbor. Consequently, several sediment quality and fish tissue studies have been conducted in the lower St. Louis River AOC, particularly since 1990, to delineate the extent and magnitude of contaminants of potential concern and to assess the potential for ecological effects (Figure 1).