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Great Lakes Research Center; Department of Biological Sciences; Department of Civil, Environmental, and Geospatial Engineering


Over a century ago, copper mills on the Keweenaw Peninsula of Lake Superior sluiced 64 million metric tonnes (MMT) of tailings into coastal waters, creating a metal-rich “halo”. Here we show that relatively small discharges can spread widely in time and space. Mass Mill (2.9 MMT) dumping into Lake Superior also illustrates the complexity of interactions with Indigenous Peoples. A combination of aerial photos, LiDAR, and a microscope technique for distinguishing end-member particles traces the migration of tailings. The clay fraction spread rapidly across Keweenaw Bay and curled into terminal L’Anse Bay, within tribal Reservation boundaries. The coarse stamp sand fraction moved more slowly southward as a beach sand deposit onto Sand Point, a sacred burial ground. Despite the partial recovery of northern beaches and southern sediments, concerns continue about chemical contamination. Mass Mill provides an excellent example of Indigenous Peoples’ territorial and resource issues with mining. A major difficulty with “legacy” discharges is that there are no longer any “responsible parties”. Initially, federal and state officials were fearful that treaty rights might warrant reparations. Recently, multiple agency/state funding programs supported international (IJC) award-winning restoration efforts by tribal members, illustrating how Indigenous Peoples and governments can work together to safeguard treaty rights.

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Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. Publisher’s version of record:

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Journal of Marine Science and Engineering

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Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


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