The largest cause of impaired uses in this AOC is the PCB contamination in the sediments. Sampling in the navigation channel revealed PCB contamination in surface sediments and more prevalent PCB contamination below the surface andis a PCB hot spot upstream of the U.S. Route 2 bridge.
Wood chips cover the sandy bottom.
The total volume of contaminated sediments in the AOC was estimated to be around 35,000 to 50,000 cubic yards. Historically, the site received water from sawmills, a paper mill, industry and a municipal wastewater treatment plant. Wastes such as paper, wood, chemicals, de-inking waste and oil from industrial users were discharged into the area. Undecomposed sawdust and woodchips still remain in the sediments from logging over a hundred years ago. Due to the presence of PCB-contaminated sediments, Manistique River and Harbor is a Superfund site.