Sediment studies: St. Louis River Area of Concern

History of sediment issues

The St. Louis River is the second-largest tributary to Lake Superior. The lower estuary culminates in the Duluth-Superior Harbor, which is the largest freshwater seaport in North America. In 1987, concerns over environmental quality conditions prompted the designation of the lower St. Louis River as one of 43 Great Lakes Areas of Concern (AOCs). This includes the segment from Cloquet, Minn., to Lake Superior.

Due to sediment contamination, the St. Louis River AOC has several impaired uses, including degradation of bottom-feeding invertebrate communities, fish consumption advisories, and restrictions on dredging. Some sediment-derived contaminants also appear to be carried by the water column to Lake Superior, the most pristine Great Lake.

In 1995, a three-phase strategy was presented to reduce impairments associated with sediment contamination (see PDF icon St. Louis River System Remedial Action Plan - Progress report (1995)):

  1. assessment studies to locate sediment hot spots (i.e., areas of elevated contamination)
  2. development of hot spot management plans
  3. implementation of remediation (cleanup) actions.

The MPCA and its collaborators conducted several sediment investigations to implement the RAP sediment strategy. Most of these pre-2006 sediment quality data were included in Phases I through IV of a GIS-based sediment quality database for the St. Louis River AOC.

More recent efforts

Sediment quality management plan. In recent years, additional effort has been made by the MPCA's Duluth office to develop a sediment quality management plan for the St. Louis River AOC in consultation with stakeholders. In turn, several new sediment investigations have been conducted since 2009, and these data are being integrated into an expanded data management system. Additional efforts by the MPCA's Duluth office and their collaborators in the St. Louis River AOC are described on the St. Louis River Area of Concern and the St. Louis River Area of Concern sediment cleanup sites webpages. This includes a PDF icon Remedial Action Plan Update for which the PDF icon Appendices include a large sediment characterization report.

Beneficial use impairments (BUI). A set of delisting targets was developed through a stakeholder input process facilitated by the nonprofit St. Louis River Alliance, with final delisting targets established by the MPCA and Wisconsin Department of Natural Resources for nine beneficial use impairments (Dec. 2008): PDF icon Final delisting targets

U.S. EPA has removed the BUI for Degradation of Aesthetics (Aug. 2014) and Fish Tumors (2019).

Assessment studies

A list of older contaminated sediment projects, either led by the MPCA or by partners, are listed below from the most recent to the oldest.

Hot spot management plans

Minnesota Slip Sediment Investigation and Remedial Evaluation.

Sediment Remediation Scoping Project for Minnesota Slip, Duluth Harbor.

Remediation projects