- Deer Lake Area of Concern On October 30, 2014, the US Environmental Protection Agency announced that the Deer Lake Area of Concern was "delisted" or removed from the international list of Great Lakes AOCs.
Deer Lake is a 906 acre impoundment located in central Marquette County in Michigan's Upper Peninsula and is connected to Lake Superior by the Carp River. The Deer Lake Area of Concern includes Carp Creek below the former Ishpeming Wastewater Treatment Plant, Deer Lake, and the Carp River to Lake Superior. Disposal of mining reagents, byproducts and materials, unacceptable by today's standards, resulted in the contamination of sediments with high levels of mercury. The lake was also historically enriched by inadequately treated sewage discharges from the area.