A tale of tailings

Eagle Mine seeks permit change related to waste dumped in Humboldt pit

ISHPEMING — Area residents were given the opportunity Monday to weigh in on a proposed change in operations at the Eagle Mine’s Humboldt Tailings Disposal Facility.

Lundin Mining Corp., the parent company of the Eagle Mine, requested an amendent to a Michigan Department of Environmental Quality permit issued in 2010 which would allow the company to place tailings, the waste material generated when processing ore, at a higher elevation than what is currently permitted in the Humboldt pit.

The orignal permit required the surface elevation of tailings not to exceed 1,420 feet above sea level in the 350 foot-deep Humboldt pit. The proposed amendment, if approved, would allow tailings to reach 1,515 feet above sea level.

The additional deposits would result in a water depth of about 20 to 25 feet from the surface of the pit to the tailings at the closure of mine operations.

Lundin Mining began depositing sulfide-rich, nickel-ore tailings from the Eagle Mine into the water-filled pit in 2014. The practice is expected to continue until the mine closes early next decade. The exact date is dependent, in part, on whether a more recently discovered ore deposit called Eagle East is extracted.

According to the permit amendment request, operations at the Humboldt Mill will not need to be modified to process the additional material.

“Eagle and Eagle East ore will be blended to achieve an optimal grade for recovery and the facilities will continue to operate similarly to current production rates,” the amendment states.

Joe Maki, spokesman for the Upper Peninsula district office of the DEQ’s Oil, Gas and Minerals Division, said there are several factors that make the proposed permit amendment significant, including the change in elevation of the tailings in the pit and the subsequent reduction in water depth covering the tailings, as well as the changing geochemistry in the pit.

“It is going to change as a result of Eagle East ore, which has higher salt quantities in it, and some of the mineralogy is a little bit different,” Maki said. “There is potential for environmental impact and that’s the significance of this.”

Attendees asked a variety of questions, with the chief concern being the water quality in the pit, and the environmental impact when that water is eventually released into the surrounding area with other local groundwater sources.

According to the Eagle Mine website, once pit water quality meets discharge limits, surface water will flow to the adjacent wetland and, ultimately, the Middle Branch of the Escanaba River.

Upper Peninsula Environmental Coalition member Kathleen Heideman said more information should be gathered by the DEQ before the permit amendment is approved.

“I am concerned that some of these problems that are related to the tailings elevation are not being seriously considered in this,” Heideman said. “Refining predictive changes is what this permit should be about for the Upper Peninsula of Michigan, because the property will be returned to the people of Michigan.”

Heideman commented on what she called the company’s “dismissive” attitude toward an environmental assessment to consider impact that additional tailings might have.

“That’s crazy,” Heideman told Maki. “You just said that there are geochemical changes taking place in the pit. We know that they are going to add almost double the volume of tailings to the pit. They’re a different quality. Eagle East had more metals in them, they certainly have more salts along with the ore, along with the waste that’s going into that pit. I draw your attention to a statement that the company made that no other changes are going to be required for water treatment — that water treatment was sufficient.”

Eagle Mine environmental and permitting engineer Jennifer Nutini acknowledged there will be changes in the geochemical make-up of the Humboldt Tailings Disposal Facility, but the company has monitored those changes regularly since the first tailings were deposited, she said.

“Eagle has several years of geochemical data,” Nutini said in an email. “Since geochemistry is a specialized field and considers many factors, Eagle’s robust geochemistry and tailings monitoring program is analyzed by a consultant so that a holistic approach can be taken to data interpretation. Eagle has provided accurate and transparent interpretation of the information in annual reports, meetings with regulators and concerned citizens, public forums and a sponsored educational session regarding the outcome of those data collection events and the evolution of the HTDF chemistry over time.”

Nutini said while the focus is on the tailings because they are being added to the pit permanently, their impact on the water quality should be minimal, because once the practice of depositing tailings stops, the chemicals associated with them will no longer be added the pit.

“It is important to understand that tailings themselves do not contribute to chemistry changes,” Nutini said. “Rather it is the the slurry water that carries them to the HTDF that influences chemistry of the bottom of the HTDF. To ensure that this is the case, during operations and for a period when tailings placement stops, the company will operate a water treatment system to remove the amount of metals and dissolved solids that will have accumulated in the HTDF from the slurry water.”

Tim Dombrowski, a technician with the Keweenaw Bay Indian Community’s Natural Resources Department, said he wanted to be sure the end use of the pit lake, once Lundin had concluded operations, was being considered during the proceedings.

“Once Eagle Mine is shut down and mining is complete, I think there should be a little bit more remediation thought put into this pit lake,” Dombrowski said, later adding, “If it is going to be a recreational lake, the integrity of the lake, the mechanical integrity of the lake should be really looked at too.”

Maki said as a condition of the original permit, the company will have to perform reclamation on the Humboldt pit site.

“As of right now, the statutes require them to reclaim the whole facility — level it, grade it, seed it and bring it to as close to a self-sustaining ecosystem as possible,” Maki said. “The pit lake will be required to reach a chemical equilibrium before they are allowed to discharge water and allow it to freely leave.”

Maki said the the decision on whether to grant the permit will ultimately be made by DEQ offices in Lansing in the next few weeks. The DEQ will accept written public comments until Dec. 26.

“What we are going to be doing in the next few weeks is drafting up a request for more information. I always say, it’s not if, it’s what,” Maki said. “We have yet to review an application for mining that we did not request additional information.”

Anyone interested in submitting commenting about the permit amendment can email DEQ-Mining-Comments@michigan.gov including “Humboldt Mill Amendment Request” as the subject. Comments can also be mailed to DEQ Humboldt Mill Amendment Request, Oil Gas and Minerals Division, 1504 W. Washington St., Marquette 49855.

Lisa Bowers can be reached at 906-228-2500, ext. 242. Her email address is lbowers@miningjournal.net.