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Manistique Harbor & River Site Ecological Risk Assessment

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Manistique Harbor and River Site, Manistique, Michigan (PDF) (9.4 MB)

Site Background

A baseline ecological risk assessment (ERA) was prepared to evaluate the post-dredging conditions in the Manistique Harbor and River Area of Concern (AOC). The Manistique Harbor and River AOC has been impacted by point and non-point sources of pollution. The harbor and river sediments contained elevated levels of polychlorinated biphenyls (PCBs) primarily from industrial and paper milling operations. Dredging commenced in 1996 and was completed in 2000. Information and data collected during the post-dredging site investigation in September 2004 serves as the basis for this task. The site investigation data, combined with the results of the ERA and the Human Health Risk Assessment, will provide the information needed for development of the overall long-term management strategy for the Manistique Harbor and River.


Overall, the HQ analysis indicates that exposure to PCBs by piscivorous birds and mammals poses little to no risk to the eagle and the mink. The HQ analysis indicates potentially unacceptable levels of risk to benthic organisms and bottomdwelling species. However, the substrate provided by the Harbor and River is not expected to support a thriving benthic community. The highest tissue residue concentrations were measured in bottomdwelling species, which have high lipid contents. The higher the lipid content, the higher the resistance to the toxicant. Since there is a potential for adverse effects on benthic organisms and fish, continued monitoring of sediment and fish tissue is recommended.

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