The St. Clair River Area of Concern (AOC) is one of 43 AOCs designated in the Great Lake basin. It extends 64 kilometres from Lake Huron to Lake St. Clair and includes the St. Clair Flats from St. John's Marsh in the west, to the southern tip of Seaway Island, and east to the north shore of Mitchell's Bay on Lake St. Clair. The River and its watersheds cover over 335,000 hectares and are home to over 170 000 people, many of whom rely on the river for drinking water.  

The St. Clair River became an AOC based on a number of beneficial use impairments (BUIs). There were twelve BUIs identified as being impaired (I) or requiring further assessment (RFA) including: Restriction on Fish and Wildlife Consumption (I); Tainting of fish and wildlife flavour (RFA);  Degradation of fish and wildlife (RFA); Fish tumours or other deformities (RFA);  Bird (or other animal) deformities or reproduction problems (RFA);  Degradation of benthos (I);  Restrictions on dredging activities (I);  Restrictions on drinking water consumption or taste and odour problems (I);  Beach closings (I) Degradation of aesthetics (I);  Added costs to agriculture or industry (I); and Loss of Fish and Wildlife Habitat (I).  

   In order to improve the environmental conditions of the AOC, a Remedial Action Plan (RAP) has been developed for the St. Clair River. The St. Clair River RAP is a partnership between Canadian and U.S. federal governments, provincial (Ontario) and state (Michigan) governments, with cooperation from the public and stakeholders through the St. Clair Binational Public Advisory Committee.   Environment Canada and the Ontario Ministry of the Environment are the lead government agencies for the Canadian side of the St. Clair River Remedial Action Plan. The St. Clair Region Conservation Authority is working with these agencies to assist in the local implementation of the plan.