Water pollution risk from Mt Milligan: First Nation

The Nak’azdli Whut’en First Nation is accusing the British Columbia government of weak oversight at Centerra Gold’s (TSX: CG; NYSE: CGAU) Mount Milligan mine by changing approvals after the operation began releasing mine-affected water the original authorization did not allow.

Mount Milligan was approved as a closed-loop, “zero discharge” site but the Nation said it releases about 2 million cubic metres of water a year through “diffuse non-point source discharge.” The Nation said the water carried sulphate that had spread into a neighbouring lake, with levels exceeding healthy guidelines. The mine is about 155 km northwest of Prince George.

“By retroactively approving activities that violated the original Environmental Assessment Certificate, the province is signalling that these conditions are legally meaningless,” Chief Colleen Erickson said in a release on Monday. “That undermines the integrity of the Environmental Assessment process and public confidence in environmental protection.”

The dispute adds pressure to B.C.’s water management at operating mines, where regulators lean on permitting, monitoring and “adaptive management” to respond to changing site conditions while First Nations press for firm rules and enforcement when impacts emerge.

Nak’azdli said its core concern is the province’s handling of the environmental assessment and permitting system. Sulphate-containing discharge from the mine showed levels around 400 mg per litre, above the B.C. guideline it cited of 218 mg per litre.

Some sulphate readings in nearby creeks remained below guidelines but were rising, the Nation said, and warned higher sulphate can disrupt aquatic invertebrates and fish habitat by altering freshwater chemistry.

Indigenous oversight

The Nation said it would expand Indigenous-led oversight through its Guardians environmental stewardship program and use financial benefits linked to the mine’s impacts to fund monitoring in its territory, including the Nation River watershed.

It also plans to work with Keyoh holders, hereditary leaders/caretakers of an extended family’s ancestral territory in the Dakelh (Carrier) land-governance system used around Stuart Lake and in Nak’azdli territory.

The Nation also argued industrial monitoring could miss impacts that local knowledge holders could detect.

“When mine water use dries up a spring, as it has in the past, company monitors may not notice,” Erickson said. “Our knowledge holders do.”

Centerra Gold planned to engage directly with the Nation and continue site monitoring.

“Centerra has a long-standing history of collaboration and open communication with the First Nation, and we are mindful of the importance of maintaining that relationship,” Vice-President of External Affairs for British Columbia, Karina Briño, said in an emailed statement.

Briño did not address the Nation’s estimate of annual discharge volumes or its sulphate measurements in the statement.

B.C.’s Ministry of Environment and Parks rejected the idea that the province was excusing a new, unassessed impact. Seepage discharges from the tailings impoundment were included in the original environmental assessment and considered during certificate issuance, the ministry said in an emailed response.

Permitted change

However, the ministry said that at the time Mount Milligan was permitted, the province did not authorize non-point source discharges in Environmental Management Act permits, even if seepage was expected. It was therefore authorized as a “zero discharge site,” which the ministry said referred to the absence of surface-water discharges from the mine.

Since then, the ministry said, B.C. had changed how it authorizes non-point source discharges and now explicitly acknowledges them in authorization documents “for clarity.” Conditions were in place to monitor seepage and protect waterways, it said.

On accountability, the ministry drew a line between the environmental assessment certificate and the Environmental Management Act permit. It said the permit – “where conditions about seepage are found” – had not been amended yet, while the environmental assessment certificate had recently been amended but “does not refer to seepage.”

Changes to certificates and permits were sometimes required because of expansions or monitoring results and described this as part of the “adaptive management” approach the province used for complex mine authorizations, the ministry said. Those authorizations allow flexibility while guarding against unexpected environmental impacts.

Compliance

The province’s Compliance and Environmental Enforcement Branch assessed how Mount Milligan met permit conditions. The Environmental Management Act permit required the mine to monitor water quality trends, including sulphate, and to implement contingency measures and mitigation actions “where necessary to prevent impacts,” the ministry said.

The Nak’azdli still plans to work with Centerra. It recognizes the mine’s importance for local employment, including for Nation members, but warned B.C. risked undermining confidence in environmental protection if it relied on retroactive approvals instead of enforcement.

“Our goal is clean water, healthy lands and a regulatory system that works – now and for future generations,” Chief Erickson said.