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U.P. lake site of experiment to improve recovery of 'benthos' organisms

Copper mining formed the backbone of the regional economy and society in the Keweenaw Peninsula in Michigan's Upper Peninsula from the mid-1800s to the 1960s.

Tailings, also known as stamp sands, were a byproduct of copper ore processing and typically disposed of in waterways, including Torch Lake.Torch Lake was designated as part of the Torch Lake Superfund Site in 1986 and as a Great Lakes Area of Concern in 1987 (Torch Lake AOC).  These designations were, in part, based on the degradation of the organisms (benthos) that live in the sediment or near the bottom of Torch Lake because of metals, particularly copper, within the stamp sand sediments. Natural sedimentation over time was the method selected to allow for the recovery of the benthos. The natural rate of sedimentation and benthic recovery has been limited when compared to baseline studies completed in 1999 and 2000.

EGLE's Water Resources Division convened a technical summit in 2019 to explore options to improve abundance and diversity of benthos in Torch Lake. The summit took the form of a design charrette and facilitated input from scientific experts, policy makers, construction experts, and other stakeholders. The technical summit participants reflected local, tribal, state, and federal perspectives. The summit resulted in plans to guide construction and monitoring of a series of pilot-scale sediment capping and habitat restoration test plots.

In 2020 an assessment of the benthic macroinvertebrate community and the quality of sediments, pore water, and groundwater were conducted in each of the experimental areas to determine baseline conditions.

The pilot-scale sediment capping and habitat restoration test plots were constructed in 2021 and will be monitored periodically to determine if sediment capping and/or habitat restoration result in increase in the density and diversity of the Torch Lake benthic macroinvertebrate community.

If the experiment indicates the potential to enhance the natural rate of benthos recovery, large-scale implementation of possible measures will be evaluated.

Photo caption: Constructed wetland experimental plot at Torch Lake in Keweenaw County in the Upper Peninsula.

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