Public views wanted on potential river cleanup

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 for the sites. The public is invited to review the cleanup alternatives by studying the plans online and commenting to the MPCA.

The Scanlon Reservoir site is east of Scanlon and downstream of Cloquet. The site is approximately 40 acres and bounded by forested lands owned by electricity provider Minnesota Power and paper mill owner Sappi. The Thomson Reservoir site is a 339-acre area located just north of Thomson. Minnesota Power operates it as a water storage reservoir for the Thomson Hydro Station farther downstream.

The studies found dioxins and furans in bottom sediments in some parts of the reservoirs. 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 contain varying levels of the same dioxin and furans. The contaminants in the Scanlon and Thomson reservoirs potentially lead to the following impairments including:

• Restrictions on dredging

• Fish consumption advisories

• Harm to the environment where insects and vegetation live at the sediment surface

Mitigation ideas include dredging the reservoirs or covering and containing the contaminated areas with sand or carbon material. Dredging and adding a layer of protective sand or carbon material is the most expensive option. Plan costs for the Thomson Reservoir range from $10 million to $54 million. The estimates for the smaller Scanlon portion are $3 million to $10 million.

The St. Louis River Area of Concern is one of 43 such areas in the Great Lakes region designated by the U.S. and Canada, where a century of industrial and shipping activities in the area left environmental damage. In 2013, the MPCA, 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 =pollution in the St. Louis River.

The St. Louis River is the largest U.S. tributary to Lake Superior and has a special significance in the region. It is a geographic boundary for Wisconsin and Minnesota, and provides access to Lake Superior which is vital to regional shipping. Development along the waterway during the past 130 years has added to contaminated sediments and caused 73 miles of the St. Louis River to be designated as an Area of Concern.

See the MPCA web site for more information on the specific alternative remedies for the Scanlon and Thomson reservoirs sites. Submit written comments by 4:30 p.m. on Aug. 31 to Steven Schoff, MPCA, 520 Lafayette Road Lake North, St. Paul, MN 55155-4194. The MPCA will consider all public comments, along with stakeholder input, in selecting the final cleanup remedy.

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Some pollution history

Background on the reservoirs from Minnesota Pollution Control Agency studies:

Scanlon

Little is known about the area of the Scanlon Reservoir prior to 1922. Records indicate that it was the site of the old Scanlon wagon bridge. In 1922, the St. Louis River Improvement Company began construction of the Stevens Dam, now referred to as the Scanlon Dam.

The site has been used for hydroelectric generation since construction was completed in 1923. Historical discharge directly to the river, upriver of the site, includes the following: municipalities, building materials manufacturing, paper manufacturing, and match manufacturing. There is little detail available on the chemical constituents of the discharges as research is being completed on historical industrial activities in the area.

Thomson

The Thomson Reservoir was constructed in 1908 and consists of multiple earthen or concrete dams used to control water flow through the south portion of the area. Water enters the site from the northwest and the northeast, from the St. Louis River and Midway River. Water discharges from the site are primarily through sluiceways to the Forbay Channel for power generation and is also routed through two dams which empty to the river immediately upstream of the Highway 210 Bridge.

The dams function as hydroelectric and water level control dams and are operated by Minnesota Power. The site is the second slow water reservoir downstream from Cloquet. Scanlon Reservoir is the first. As the St. Louis and Midway rivers discharge to the site, flow slows due to channel expansion, resulting in the deposition of sediments. Since its construction, fine sediment buildup has occurred behind the dams and depositional areas within the reservoir basin.

The site is immediately downstream of historical industrial waste water discharges associated primarily with municipal discharges, building materials manufacturing, and paper manufacturing. These waste streams were removed from the river in 1979 when they were rerouted to Western Lake Superior Sanitary District.