Minnesota Pollution Control Agency details cleanup options for Scanlon, Thomson reservoirs

The contaminants potentially lead to restrictions on dredging as well as fish consumption advisories, among other impairments.

Thomson and Scanlon reservoirs.jpg

The Minnesota Pollution Control Agency has released studies of two contaminated sites, the Scanlon and Thomson reservoirs, in the St. Louis River Area of Concern that detail cleanup options, according to a news release from the agency.

The public is invited to review and comment on the cleanup alternatives.

The Scanlon Reservoir site is located immediately east of Scanlon and downstream of Cloquet. The site is approximately 40 acres and bounded on all sides by forested lands owned by Minnesota Power and Sappi Cloquet LLC.

The Thomson Reservoir site is a 339-acre reservoir located just north of Thomson. Minnesota Power operates it as a water storage reservoir for the Thomson Hydro Station further downstream.

The studies found dioxins and furans in bottom sediments in some parts of the reservoirs, the release said. This contamination likely affects the smallest organisms at the bottom of the food chain, called benthic invertebrates, which live in or on the bottom sediments of rivers, streams and lakes.


As fish and birds consume these tiny organisms, the contamination moves up the food chain. Studies confirm that fish within the reservoirs also contain varying levels of the same dioxin/furans.

The contaminants in the Scanlon and Thomson reservoirs potentially lead to the following impairments:

  • Restrictions on dredging;
  • Fish consumption advisories;
  • Harm to the benthnic environment where insects and vegetation live at the sediment surface.

The St. Louis River Area of Concern is one of 43 areas of concern in the Great Lakes designated by the U.S. and Canada, where historic activities left a legacy of significant environmental damage, the release said.
In 2013, the Minnesota Pollution Control Agency, Minnesota and Wisconsin departments of natural resources, and the Fond du Lac Band of Lake Superior Chippewa developed a comprehensive plan to address these legacy damages, including historic pollution in the St. Louis River Area of Concern.

Go to and click on "St. Louis River Area of Concern sediment cleanup sites" for more information on the specific alternative remedies for the Scanlon and Thomson reservoirs sites.

The MPCA will consider all public comments, along with stakeholder input, in selecting the final cleanup remedy.

Written comments must be submitted by 4:30 p.m. Aug. 31 to Steven Schoff, MPCA, 520 Lafayette Road North, St. Paul, MN 55155-4194.

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