Sulfide Mining: Spruce Road Acid Mine Drainage

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Toxic mining pollution discovered two miles from Boundary Waters
Canoe Area Wilderness.

Acid mine drainage near the Spruce Road in northeastern Minnesota

Oct. 2, 2010 — The Friends of the Boundary Waters Wilderness has discovered that a sulfide mining exploration site just two miles from the Boundary Waters Canoe Area Wilderness is creating acid mine drainage 36 years after a mining company dug up ore as part of exploration efforts. The research is the focus of a story in today’s Minneapolis Star Tribune.

Drainage from the site contains copper, arsenic and other metals at levels which are harmful to aquatic life and human health. It is located on the Spruce Road, approximately 15 miles southeast of Ely and about two miles from the South Kawishiwi River and Little Gabbro Lake BWCAW entry points. (See interactive map.)

The Minnesota Pollution Control Agency (MPCA) cannot demonstrate that it has monitored the site whatsoever since 1976 and, when asked about the lab results, the MPCA informed the Friends that the agency is unlikely to take any action to further analyze the drainage or reclaim the site to prevent the toxic pollution from continuing.

“The lab results fly in the face of what mining companies and our state agencies have been telling the public,” says Betsy Daub, Policy Director for the Friends. “The fact is that Minnesota’s sulfide ore is capable of producing toxic acid mine drainage, and the Pollution Control Agency and Department of Natural Resources have not addressed it for over 30 years.”

Ground Zero for Twin Metals

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The Spruce Road site is in the heart of the area now being targeted by the Twin Metals mining project, a joint venture between Vancouver-based Duluth Metals and Chilean mining conglomerate Antofagasta PLC. The site was excavated by International Nickel Company (INCO) in 1974 as a “bulk sample,” a mineral exploration activity that is much like a small-scale strip mine.

While the Spruce Road site may be generating a relatively small flow of toxic drainage, the excavation was far smaller than any proposed mine. The INCO project excavated about 10,000 tons of ore. The Twin Metals mine proposal would extract approximately 40,000 tons of ore each day.

A spokesman for Twin Metals has previously stated that sulfide content in the ore body would be too low to cause acid mine drainage concerns. In a story by Minnesota Public Radio this June, David Oliver stated, “”[Waste rock] is deemed below any threshold that would generate acid drainage. It just doesn’t have enough sulfur to do it.”

Toxic Soup

The Spruce Road site drainage is not acidic but the presence of the metals indicates acidity which would have leached the metals out of the rock before reaching the point at which sampling was possible. The acidity is apparently being neutralized before reaching the discharge point, but is likely responsible for the high levels of metals.

National mining expert Dave Chambers of the Center for Science in Public Participation in Bozeman, MT has reviewed the lab results and stated that the drainage meets the commonly-accepted definition of “acid mine drainage.”

Drainage from the site is currently flowing into a small wetland. The Friends took samples of the drainage at the mouth of a small culvert, and from a creek below the wetland. The results of analysis of both samples is included in documents below. Chemical levels in the sample taken below the wetland are significantly reduced over those emanating from the discharge source, but some levels are still above water quality standards. The drainage’s effects on the wetland are at this time unknown.

Media Coverage

Resources for Public and Media

The Friends is making available significant documentation and resources regarding the Spruce Road site. The documents below provide in-depth information regarding the history of the site, early efforts to mitigate the pollution, and the results of the Friends’ lab analysis of the samples taken from the site this summer.

The Minneapolis Star Tribune‘s Tom Meersman broke the story in the Oct. 2 newspaper:

Runoff from old mines raises fears

Pollution problems near the Boundary Waters are raising concerns about future Minnesota mining projects.

Environmental groups have found high concentrations of metals leaching into streams and wetlands from two long-closed sources: one old test mine and one abandoned mine. The pollution runs off waste rock excavated decades ago and piled at the sites.

Alerted by a resident near Ely, Friends of the Boundary Waters collected samples of the seeping water at one of the sites this summer.

An independent lab analysis confirmed that it contained arsenic, copper, nickel and iron at concentrations hundreds of times higher than state water quality standards allow for chronic exposure.

“These are toxic levels to animal life, and the arsenic is too high for humans,” said Betsy Daub, policy director for Friends.

The story also covers the Dunka Pit, a nearby site where sulfide ore was inadvertently excavated by a taconite company and has since been polluting Birch Lake:

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 not far from the Boundary Waters. An average of 300,000 to 500,000 gallons runs off them each month, according to MPCA documents.

Oct. 4, 2010 update – The Duluth News Tribune has published an updated story about the Spruce Road site. It includes statements from the PCA that they might perform additional analysis and remediation work as a result of the publicity the Friends has brought to the issue:

Group says acidic runoff leaving ’70s copper site near BWCAW

A state PCA official said Monday that publicity about the study might prompt his agency and the DNR to retest the site.

Richard Clark, a hydro-geologist with the Minnesota Pollution Control Agency, said the lab results “make sense, they don’t surprise me’’ but that a recent site inspection showed little or no runoff moving into nearby streams or rivers.

Neither the PCA nor DNR has sampled the site since 1976.

Clark said he visited the site two weeks ago when concerns were first brought to his attention and that he found it dry, with no runoff. He said he’s been to the site several times in recent years and not seen any environmental damage as rainwater percolates through a pile of waste rock from the test mine and slowly seeps out.

“There was a report issued in 1974 when the mining was completed that said the volume and nature of the discharge at that site didn’t pose any threat” to nearby waterways, Clark said. “The decision in the 1970s (not to conduct further tests) predates my arrival here. But it’s my guess that report is why testing was discontinued.”

Clark said PCA and DNR officials are discussing whether to retest at the site after the friends group’s finding.


The below photos were taken of the Spruce Road acid mine drainage site on August 15, 2010. Click the images to see a larger version. Click that image to download a high-resolution version.

Media outlets are permitted to use these photos without any additional clearance required. Please just let us know at if you do use them.

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