The Fond du Lac Band, one of six Native American tribes that make up the Minnesota Chippewa Tribe, has challenged the state environmental agency over its issuing of a permit for US Steel’s Minntac iron mine.

Representatives of the Band have lodged an appeal with the Minnesota Court of Appeals, after the Minnesota Pollution Control Agency (MPCA) granted an extension to a permit first issued in 1987, enabling operations to commence at the Minntac mine.

However, the Band believes that the new permit, first drafted in 2016, does not include strict enough clauses to prevent the mine’s tailings from posing a health risk.

“We realise that the mining industry makes an important contribution to our area’s economy and people’s livelihoods,” said the Band’s tribal chairman Kevin R Dupuis Sr. “But we think it is only reasonable to expect companies profiting from the extraction of Minnesota’s mineral resources to comply with environmental laws and clean up any environmental damage caused by their operations.”

The Band is particularly concerned with the release of sulphate into local water sources, including groundwater and wild rice waters, which has the potential to damage local flora and rice crops respectively.

In 2011, US Steel predicted that sulphate concentration in the mine’s tailings would reach 1,018mg per litre (mg/L) by 2033.

As part of its permit, the MPCA acknowledged that sulphate would be “the pollutant of greatest concern” to health and safety, and set an upper limit on sulphate concentration in local water sources of 357mg/L. The agency pledged to monitor sulphate levels for ten years from the mine’s opening, and would consider withdrawing the permit should the concentration of sulphate rise above this level.

The Band believes that this limit is both too high and too loosely enforced to ensure public safety.

The MPCA reported that the average concentration of sulphate in Minnesota waters is just 19mg/L, allowing the Minntac mine to exceed the average sulphate level by more than 15 times and still be well within its permit. The MPCA also did not insist on any immediate changes as part of the renewed permit, instead insisting that US Steel lowers the levels of sulphate in the mine’s tailings over a decade from 2016. Band members fear that this could lead to significant environmental damage in the immediate term.

The Minntac mine has an annual production of around 16 million tonnes of iron ore pellets, mined from an iron-bearing rock known as taconite, which is processed on-site.

The mine is one of two in the region owned by US Steel, alongside the Keetac operation, which produces six million tonnes of pellets each year.

Mining Technology’s Mining Safety content is supported by USA mining safety specialists Carroll Technologies Group.