HIBBING — Within a small, fenced field a few blocks from the Hull-Rust, the world’s largest open pit mine, 812 tons of rock from the Duluth Complex near Babbitt is under study by Minnesota Department of Natural Resources Division of Lands & Minerals researchers.
“There were several rock test piles from the AMAX Mesaba (copper nickel exploratory) site that were near the exploratory shaft site near Babbitt,” said Steven Koski, research scientist at the DNR Lands and Minerals facility in North Hibbing. “There was also originally a small research facility with Lands & Minerals in the town of Babbitt. Around the same time of decommissioning of the test piles, the Babbitt facility also closed, rock from some of those piles was moved to our Hibbing field site, and research subsequently picked up at the Hibbing office. It’s considered the longest leachate testing of the characteristics of rock from the Duluth Complex.”
The Duluth Complex in northeastern Minnesota is one of the world’s largest undeveloped copper, nickel and precious metals reserves. Estimates are that it contains more than four billion tons of reserves.
The history of the rock pile in Hibbing goes back a long way.
Deposits of copper-nickel were first found in the 1950s near Babbitt.
AMAX Exploration, Inc., in 1976 sunk a test shaft near Babbitt and in 1977 constructed six lean ore rock piles from the site. The piles remained near Babbitt until being moved to Hibbing.
Including its time in Babbitt, the AMAX rock pile has for 41 years provided data on the leachate (liquid that can pass through a solid) characteristics of nonferrous rock from the Duluth Complex.
In simple terms, it means the DNR has for decades studied and collected information from the pile about how rocks from the Babbitt area interact with water.
A high-tech monitoring system in Hibbing, including a membrane beneath the rock pile, water collection, water treatment, and water storage facility, help DNR researchers compile data.
“We know that when you have high sulfur in the host rock, you have the potential for acid drainage,” said Peter Clevenstine, DNR Lands & Minerals assistant director. “We also know that other minerals tend to be basic and can neutralize acidity. We’re looking to see how those elements react as rocks weather over time. We have tested water run-off over time. We have a better understanding of water treatment that may be required, depending on the rock mineralogy. And how stockpiles can be designed and built to avoid potential harmful effects.”
In addition to the rock from Babbitt, the Hibbing facility is also testing the leachate effects of four 65-ton piles of Ely Greenstone rock.
The field site in Hibbing, atop a small hill behind the DNR’s Lands & Minerals offices, is a little-seen tool that’s helping the DNR complete scientific research to support safe mining.
A research laboratory within the Hibbing offices compliments the work conducted outdoors.
The laboratory, in a series of humidity cells containing rock samples from around the region, examines the effect of water applied to the rocks over the long-term.
Research performed by DNR Lands & Minerals is done under state statute. The statute calls on the DNR to control possible adverse environmental effects of mining, preserve natural resources, encourage the planning of future land utilization, promote the orderly development of mining, encourage good mining practices, and recognize and identify the beneficial aspects of mining,
“Because of the research we do, we have a much better understanding today of rock weathering,” said Clevenstine. “It gives us much more confidence about how rock will behave that will be in rock stockpiles for decades or centuries.”
The DNR office in Hibbing also studies leachate quality from tailings basins, the impacts of disposing tailings in existing open pits, mitigation techniques, treatment systems, the application of waste products for mineland reclamation, reclamation techniques, and subaqueous (underwater) mine waste disposal. Research on decreasing mercury emissions from taconite plants has also been conducted by the DNR.
Since the 1970s, the DNR has researched environmentally sound ferrous and nonferrous mining along with peat and dimension stone mining.
Research partners have included the University of Minnesota, mining industry, U.S. Environmental Protection Agency, U.S. Bureau of Land Management, U.S. Army Corps of Engineers, and Western Governors’ Association.
Knowledge gained through research in Hibbing is used to support sound environmental review and permitting decisions for minerals projects within the state.
“We feel much more confident today in safeguarding our water in northeastern Minnesota because of the data collected from the research,” said Clevenstine. “The research we do is to help mine projects get permitted with good permits so we can sustain economic activity and sustain our natural resources.”
Mining companies – which benefit on a large scale from the small scale research done in Hibbing – have formed a cooperative relationship with DNR Lands & Minerals, said Koski.
“A lot of the time, we are trying to answer similar questions,” said Koski. “So, it’s kind of a mix of both. Sometimes, we do projects at the mines as well as at Hibbing.”
Clevenstine says the research is beneficial to all stakeholders.
“When this program began in the 1980s, it was done to give us confidence in our internal decisions on mine permitting,” said Clevenstine. “But today, the research we do is a tremendous asset to the public in giving the public confidence.”
Beyond Koski and one summer worker in Hibbing, three DNR researchers in St. Paul also work on research projects.
Currently, the researchers are working on ten different projects, said Koski.
Among the projects are sulfide oxidation rates, sulfur cycling in wetlands, and testing a variety of membrane liners in cooperation with the University of Illinois.
For Koski, a 2008 graduate of Hibbing High School and 2014 chemistry graduate of the University of Minnesota Duluth, the research has personal meaning.
Koski’s father worked in a mine. And Koski enjoys northeastern Minnesota’s vast outdoor recreational opportunities.
“It’s always rewarding,” Koski said of the research. “To be able to advance science and understand the environment around you, it’s a nice to feel like you’re making a difference in an area you care about.”
DNR Lands & Minerals research reports are available on the agency’s web site.