The US Department of Interior on Tuesday released a Solicitor’s Opinion outlining new rules for mining sites that use federal lands to store waste rock and tailings facilities, removing one of the last remaining obstacles to Lithium Americas’ Thacker Pass mine project.

The decision came after a review found that almost all of the mine site located in Nevada contain lithium ready for extraction.

In February, a federal judge rejected claims that the project would cause unnecessary harm to the environment, but ordered officials to study whether an area of roughly 1,300 acres , which will be used to store waste rock, also contains the metal. The court passed a separate order allowing construction to begin on the project.

The judge’s order for the review is linked to a separate court ruling that found mining companies do not necessarily have the right under US law to store waste rock on federal land that does not contain valuable minerals, potentially complicating planned land usage at the Thacker Pass mine.

However, of the dozens of mining claims at the site, the US government found that less than 10 did not contain lithium mineralisation, an Interior Department official told Reuters. “They’re going to be able to start construction and production without these claims being in the plan of operation,” the official said of Lithium Americas.

Jon Evans, the CEO of Lithium Americas, said to Reuters: “We’re committed to doing this job right and meeting or exceeding state and federal regulations as we advance construction.”

At the beginning of March, Lithium Americas began construction on the Thacker Pass project, despite outcry from campaign groups claiming the environmental review process had been rushed. Conservation group Great Basin Resource Watch said in 2021 that analysis undertaken to approve the project had been completed in a much shorter time that was usual, and that the company has failed to receive community consent.

Great Basin Resource Watch is appealing the latest court ruling on the grounds that federal law only allows Lithium Americas access to the land if lithium is found consistently in quantities that are economical to extract. “It stands to reason that the mining company would not place millions of tonnes of waste material on an area where they see valuable mineral deposits,” said John Hadder, a member of the group.

The Solicitor Opinion, which was filed under the 1872 General Mining Act,  known as the Mining Law, seeks to make accessing permits for mining operations in the country easier and more consistent.

“As we work across the Biden-Harris administration to provide clarity for the permitting and exploration of energy resources in the United States, today’s Opinion will support the timely review of mining proposals on federal lands and is one step of many the Department of the Interior is taking to update guidance for mining companies to reflect the realities of the 21st century,” deputy secretary Tommy Beaudreau said in a government statement.