Carbonless copy paper manufactured between 1957 and 1971 contained polychlorinated biphenyls  (PCBs) as an ink carrier. Such paper was recycled by paper mills on the Kalamazoo River and  Portage Creek, resulting in the discharge of PCBs. Although PCB use in the manufacture of carbonless copy paper was discontinued in 1971, the waste streams of the Kalamazoo area paper mills most likely contained PCBs for several years after 1971.  The PCB-contaminated wastes from these paper mills were discharged directly to the Kalamazoo River and Portage Creek.  In later years, waste effluents were sent to clarifiers prior to being discharged to the river and creek. The bottom sludge from these clarifiers was placed in at least five disposal areas along the river and creek. The clarifiers were ineffective for stopping the discharge of PCBs because the PCBs were associated  with the suspended fine grained clay particles that did not settle during clarification.

A biological survey completed by the Water Resources Commission (predecessor to the DEQ and now EGLE) in 1971 identified significant levels of PCB-contamination in fish and other aquatic animals in the Kalamazoo River.  A follow-up investigation was completed in 1972 which identified PCB contamination in river water and sediments from Portage Creek to the city of Kalamazoo, and identified the former paper mill operations along Portage Creek as a major source of PCB contamination.  Fish Consumption Advisories were put in-place for multiple species in 1979 and remain in-place today.  From the early 1970’s until 1990, testing and studies of the river, soil, sediments, biota, paper mil properties, and former paper mill disposal areas were completed by various parties to determine the extent of PCB contamination and risks to human health and the environment.  On August 30, 1990 the Kalamazoo River Superfund site was added to the National Priorities List, giving it official designation as a Superfund site.