In 1987, under the Great Lakes Water Quality Agreement between Canada and the United States, 43 areas of concern (AOC) were identified as having experienced significant levels of environmental harm. Of these 43 areas of concern, 12 are located in Canada and 5 are shared bi-nationally.

Once identified, Remedial Action Plans (RAPs) were developed for each AOC, aimed at “restoring water quality and beneficial uses of the ecosystem by cleaning up severely contaminated and degraded locations around the Great Lakes.”