Lundin Mining Corp. is seeking permission from the Michigan Department of Environmental Quality (DEQ) to construct a tunnel at its Eagle Mine that to a second ore body that would extend the line of the mine into 2023.
Lundin has asked DEQ to amend Eagle Mine's Part 632 mining permit and allow the company to finish tunneling to a nearby high-grade nickel and copper deposit called Eagle East.
Eagle Mine began constructing the Eagle East tunnel ramp in July, but needs DEQ approval to advance the tunnel all the way to the second ore body, Michigan Live reported.
The DEQ is deciding whether the tunnel amounts to a "significant" permit amendment, and thus require a more stringent public review with a hearing and comment period. The DEQ has until mid-March to formally make that call.
The company notified the DEQ of its tunneling plans last May and on Feb. 16, formally requested its “current and future” tunnel development be included in its existing permit by amendment.
Another permit would be necessary to begin extracting Eagle East ore which is about 2,500 ft below the initial deposit.
Eagle began extracting nickel, copper and other metals from the initial deposit in 2014. The mine ramped up production in 2015, but extraction of the ore is expected to gradually decline over the mine's eight-year lifespan.
Miners are technically waiting for Lundin to give approval to start developing Eagle East pending completion of a feasibility study. The deposit was discovered in 2015. Lundin bought the mine from Rio Tinto for $325 million in 2013.
“Applying for permit amendments in advance helps us ensure we’re ready to move forward when that times comes,” said Eagle Mine spokesperson Matt Johnson.
Part of that process has involved a “clarification,” Johnson said, of the mine’s lease with the DNR, which decided earlier this year the existing metallic minerals lease didn’t cover removal of waste rock from the Eagle East tunnel.
Karen Maidlow, property specialist with the DNR Office of Minerals Management, said a new retroactive lease has been drawn up that would allow Eagle Mine to remove waste rock during tunneling and cover any rock already removed.
Johnson said the mine asked the DNR to resolve the confusion last year. Rock already removed from tunneling has been stored above ground for mine backfill.
Maidlow said the new lease is the “first one of its kind.”
Presently, Eagle's permit limits the mine to hauling 2,000 tons per day. The mine says developing Eagle East would not require construction of a new tailings facility at the Humboldt Mill, a repurposed iron ore mill located about 15 miles to the south. At the mill, nickel and copper ore is separated into concentrates before being shipped by rail.
Johnson said developing Eagle East will allow the mine to extent its lifespan by a year and maintain a consistent payroll by blending high grade ore from Eagle East with declining grade value ore from the initial deposit. The mine presently employs about 400 workers full time. Aside from a trucking contractor, the employees are non-union.
The company is exploring for other mineral deposits nearby, including an extension of Eagle East. "We'd like to find more," Johnson said. "We have a robust exploration program that's been going on for a couple years."