Aquila Resources has received the National Pollutant Discharge Elimination (NPDES) permit, the third of four necessary approvals, for its zinc-rich and gold-rich Back Forty Project in Michigan, US.

The NPDES permit was awarded by the Michigan Department of Environmental Quality (MDEQ) after a comprehensive review by the US Environmental Protection Agency on 24 February.

Aquila Resources CEO Barry Hildred said: “We will continue our efforts with the State of Michigan and local communities to demonstrate our commitment to environmental responsibility and sustainable resource development that benefits all stakeholders.”

The NPDES permit regulates the effluent limitations and monitoring requirements of water discharged from the mine to the Menominee River.

Aquila Resources noted that the review process and permit decisions complies with the Federal Water Pollution Control Act, Part 31, Water Resources Protection, of the Natural Resources and Environmental Protection Act, Part 41, Sewerage Systems provisions.

The company received the Mining Permit and Air Use permit last December.

It is currently working with MDEQ to receive the final Wetlands Protection Permit, which is expected later this year.

“We will continue our efforts with the State of Michigan and local communities to demonstrate our commitment to environmental responsibility and sustainable resource development that benefits all stakeholders.”

The Back Forty Project is a volcanogenic massive sulfide (VMS) deposit situated adjacent to the mineral-rich Penokean Volcanic Belt in Michigan's Upper Peninsula.

In an updated preliminary economic assessment filed in September 2014, Back Forty indicated strong economics with a pre-tax NPV of $282m ($210.8m after-tax) and a pre-tax IRR of 38.8% (32% after-tax) based on mining 16.1 million tonnes of measured, indicated, and inferred resources over the 16-year life of mine.