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Restoring Deer Lake AOC (timeline)

Year Critical Actions

On Oct. 30, 2014, EPA announces that the Deer Lake Area of Concern has been removed from the binational list of toxic hotspots that were targeted for cleanup in the U.S.-Canada Great Lakes Water Quality Agreement. The Deer Lake Area of Concern is the first U.S. site in the Lake Superior basin to be delisted.

The Deer Lake Public Advisory Council, in conjunction with the State of Michigan, initiates the formal delisting process of the Deer Lake Area of Concern.

All BUIs have been removed from the Deer Lake Area of Concern.

  • Restrictions on fish and wildlife consumption
  • Bird or animal deformities or reproductive problems
  • Eutrophication or undesirable algae

All Management Actions Complete – The Partridge Creek diversion is the last management action necessary to delist the AOC. In total the project created approximately 1 mi. of closed culvert hydraulic conveyances, approximately 1 mi of new open stream, and 1.3 acres of restored wetlands.

Phase 2 of Partridge Creek diversion completed – created 0.5 mi. of closed culvert and 0.7 mi of open stream and constructed 1.3 acres of new wetlands.

2012 Phase 1 of Partridge Creek diversion completed – created 0.5 mi. of closed culvert and 0.2 mi. of open stream.

RAP update - outlines plans for removing the remaining BUI.

The first two beneficial use impairments are removed from the Area of Concern.

  • Bird or animal deformities or reproductive problems
  • Eutrophication or undesirable algae

MDEQ (MDNRE at the time) releases an updated BUI Restoration guide for each of the BUIs in the Michigan Areas of Concern.


MDEQ issues AOC delisting guidelines.


MDEQ observes further improvements in winter dissolved oxygen compared with previous studies.

PAC completes long-term monitoring and wildlife study – initiates removal process for BUI. 


Water monitoring conducted by PAC shows valve operation has reduced in-lake methylation by 65 percent. 


RAP update sets BUI removal goals and recommended remedies to decrease mercury concentrations in fish. 

Water quality began to be monitored weekly and improvements were observed.


Since monitoring began in 1963, bald eagles are found to be successfully reproducing when nests were occupied. Breeding remains successful today.


Mercury content of standard northern pike measures below “no consumption” trigger. 


Mercury content of brook trout measures below “no consumption” trigger. 


MDEQ determines that dissolved oxygen content during winter has improved 3 years after wastewater treatment improvements were made. 


MDNR publishes the stage I Remedial Action Plan.

Deer Lake is designated an Area of Concern.

Prior restoration projects

Some significant restoration efforts took place before Deer Lake was declared an AOC.

  • The City of Ishpeming separated its combined sewers into sanitary sewers and storm sewers by 1985.
  • An enhanced secondary wastewater treatment plant replaced the three primary treatment plants in April 1986. The new wastewater treatment system significantly decreased nutrient loading into Deer Lake; for example, phosphorus loading decreased by 86 percent.