A federal appeals court has partially overturned a lower court ruling that had tossed lawsuits again the US Environmental Protection Agency’s 2019 decision to withdraw Obama-era restrictions that had blocked a proposed Alaska copper-molybdenum-gold-silver-rhenium mine, Kallanish reports.

The 2-1 decision by a panel from the US 9th Circuit Court of Appeals sends the case back to a federal district judge in Alaska to determine if the EPA acted arbitrarily when it withdrew its proposed determination made in 2014 in connection with the proposed Pebble mine in southwest Alaska, in a ruling that favours project opponents and revives a 2019 lawsuit.

The court found that the EPA needs to consider whether unacceptable adverse effects are likely to occur when it withdraws a Clean Water Act Section 404(C) proposed determination.

The 2014 EPA determination concluded that the mining project posed too great a threat to the salmon-rich waters of Bristol Bay, effectively blocking the project. The EPA determination came before the companies had filed applications or environmental reviews. In 2019, the EPA said it would withdraw its proposed determination against the mine, triggering the lawsuit by mine opponents including Trout Unlimited.

The companies behind the mine, Northern Dynasty Minerals and its subsidiary Pebble Partnership Ltd, say in a statement that they are confident that the federal government will prevail and the eco-groups behind the lawsuit will lose when the case is reheard by the district judge.

Lawsuit supporters says the latest court action could lead to permanently blocking the Pebble mine and providing immediate protections for Bristol Bay in Alaska.

In 2020, US District Judge Sharon Gleason in Anchorage, Alaska, dismissed the challenge. The appeals court overturned Gleason’s decision, reviving the Trout Unlimited legal challenge. The case was sent back to Gleason.

The appeals court also ruled that the case is subject to judicial review. The parties had said the case could not be reviewed under an exemption to the federal Administrative Procedures Act.

Last November, the Pebble mine was rejected by the US Army Corps of Engineers. The agency says the project was non-compliant and not in the public interest. Northern Dynasty and Pebble Limited Partnership contend that the Corps of Engineers rejection of the plan was arbitrary, contrary to law, unprecedented in Alaska and fundamentally unsupported by the administrative record. The companies have appealed that decision. The appeal is expected to proceed soon through the Corps’ regional office in Hawaii.

The Pebble mine holds 6.5 billion tonnes of measured and indicated resources averaging 0.40% copper, 0.34 grammes/t gold, 240 parts-per-million molybdenum, 1.7 g/t silver and 0.41 ppm rhenium. It also hosts 4.5 billion t of inferred resources averaging 0.25% copper, 0.25 g/t gold, 226 ppm molybdenum, 1.2 g/t silver and 0.36 ppm rhenium. It would be an open-pit mine on state lands about 320 kilometres southwest of Anchorage, Alaska. It would operate for 20 years.