Background Deer Lake is a 906 acre impoundment in central Marquette County near Ishpeming. Mercury used in ore research was discharged to sewers in Ishpeming by mining laboratories for about 50 years, ending in 1981. The treatment plant was updated in 1985, but the lake remains highly productive.
Deer Lake continues to recover from effects of past municipal and industrial discharges.
Water quality conditions have greatly improved in the last seven years, but elevated levels of mercury are still a problem. This RAP described problems known at the time and identified actions and studies needed to further define and remediate those problems. However, the RAP was written before the 1987 amendments to the Great Lakes Water Quality Agreement that outlined new guidelines for RAPs. These guidelines include identifying impairments for any of the 14 designated beneficial use impairments. The primary impaired use of the AOC is fish consumption.