Dunka Mine Water Pollution

What are the concerns about the (closed) Dunka mine?

The Dunka mine, now closed, is located in the Boundary Waters watershed (Rainy River Basin), on the edge of Birch Lake. Birch Lake drains into the Kawishiwi River, which flows into Boundary Waters Canoe Area Wilderness surface waters. The Dunka Mine exemplifies many of the threats of sulfide mining, especially the concern that, once the ore is mined, the company may go bankrupt and leave water pollution poorly treated.
Location of Dunka Mine in relation to proposed sulfide mines (Quetico Superior Wilderness News map)
LTV Steel Mining Co. operated the Dunka mine from 1964 to 1994 and stockpiled more than 20 million tons of waste rock. For decades the piles – 80 to 100 feet high and extending for almost a mile – have been leaching copper, nickel, and other metals into wetlands and streams that flow into Birch Lake. In 2010, it was reported that each month an average of 300,000 to 500,000 gallons of polluted water runs off the Dunka Mine waste rock piles.
Although the Dunka Mine was a taconite mine, excavation affected millions of tons of rock in the Duluth Complex, a geologic feature that has elevated sulfate levels. Sulfate pollution from the abandoned Dunka Mine impacts numerous stands of wild rice in the Kawishiwi River, including wild rice in Bob’s Bay.

When the Dunka Mine went bankrupt, the Minnesota Department of Natural Resources (DNR) allowed the LTV Steel Mining company to shutter its on-site active water quality treatment facility and rely on “passive” treatment, provided by constructed wetlands, for control of sulfate and toxic metals.

The most recent National Pollutant Discharge Elimination System/State Disposal System (NPDES/SDS) water pollution permit issued by the Minnesota Pollution Control Agency (MPCA) in 2000 failed to set pollution limits for sulfate, toxic metals, such as copper and nickel. The permit also failed to limit specific conductance ionic pollution that kills sensitive aquatic insects and affects the health and diversity of fish and other aquatic life.
Documentation of wild rice downstream of Dunka Pit (Barr Report 2011)
MPCA also granted a variance allowing Dunka Mine discharge to exceed MPCA water quality standards. Sampling shows that Dunka Mine seeps have higher levels of sulfate and toxic metals than allowed under Minnesota water quality standards.

Research by retired chemist Bruce Johnson documented the Dunka mine’s continuing pollution and the role of specific conductance in harming fish and other aquatic life. WaterLegacy requested that MPCA issue a new permit and control Dunka Mine pollution.

The U.S. Environmental Protection Agency (EPA) has also entered into Performance Partnership Agreements with MPCA to make issuance of updated mining water pollution permits, including a new permit for the Dunka Mine, a high priority.

What’s the status of Dunka mine water pollution permits?

Despite advocacy by WaterLegacy and the MPCA’s agreements with EPA, no updated Dunka mine permit has been reissued. There has been no new review of the variance MPCA granted in 2000 to allow the Dunka mine to exceed water pollution limits. In 2015, after WaterLegacy asked EPA to withdraw MPCA’s NPDES permit authority [link to Petition to EPA due to MPCA Failure to Regulate – not drafted yet], WaterLegacy submitted a supplement to the petition to EPA focusing on MPCA’s continuing failure to regulate pollution at the Dunka mine.

What are the benefits from work on Dunka mine pollution?

Bruce Johnson’s research on harm to aquatic life from Dunka Mine pollution was incorporated into the specific conductivity report that he and Maureen Johnson, a retired biologist, prepared in collaboration with WaterLegacy. This report documents the effects of specific conductivity mine pollution on fish and aquatic life in northeastern Minnesota. The Johnsons’ report supported important EPA research on implementing specific conductance limits in Minnesota.

The work initiated by the Johnsons and the analysis done by EPA on implementing specific conductance limits in Minnesota provided the scientific support for development of a water quality standard for specific conductance by the Fond du Lac Band of Lake Superior Chippewa.