Development of a Framework for Evaluating Numerical Sediment Quality Targets and Sediment Contamination in the St. Louis River Area of Concern

The St. Louis River Area of Concern (AOC) is an important transboundary waterway between northeastern Minnesota and northwestern Wisconsin (Figure 1). This AOC contains several sites where concentrations of metals, mercury, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, and/or dioxins and furans are elevated in the sediments compared to reference areas. In areas where these chemical substances occur at concentrations that pose a known or suspected threat to environmental or human health, the sediments are designated as contaminated. Restrictions on dredging, fish advisories, and habitat impairments to bottom feeding organisms are just a few of the use impairments resulting from contaminated sediments in this Great Lakes AOC. Since the St. Louis River constitutes the second largest tributary to Lake Superior, the potential transport of sediment-derived contaminants to Lake Superior is of additional concern to many stakeholders. For general background information on sediment quality issues, see Appendix A.