A weekend court ruling has temporarily blocked winter construction at a huge ConocoPhillips oil project on Alaska’s North Slope.

U.S. District Court Judge Sharon Gleason issued an order Feb. 6 barring ConocoPhillips from starting planned gravel mining and gravel-road construction at its Willow project. With an estimated 590 million barrels of oil and the potential to produce 160,000 barrels per day, Willow would be the westernmost operating oil field in Arctic Alaska. First oil is planned as early as 2024, according to ConocoPhillips.

Gleason’s injunction came in response to an environmental lawsuit claiming the Trump administration’s Willow approval failed to properly consider wildlife and climate-change impacts. The judge last week rejected environmentalists’ request for a more sweeping injunction. Her new order halts gravel-related work until at least Feb. 20, giving the 9th Circuit Court of Appeals time to weigh in.

ConocoPhillips had intended to start blasting gravel on Feb. 12, according to Gleason’s order.

The plaintiffs have shown “there is a strong likelihood of irreparable environmental consequences once blasting operations commence,” the order said. Additionally, the plaintiffs’ arguments concerning climate change “could well be likely to succeed on the merits” at the appeals court, Gleason said.

Gleason’s order does not stop construction of seasonal ice roads, which melt away in summer.

Plaintiff representatives noted that Biden is reviewing Trump administration oil policies, including the approval of Willow.

“We’re hopeful this terrible project can be stopped, either by the courts or the Biden administration’s review,” Kristen Monsell, an attorney with the Center for Biological Diversity, said in a statement on Feb. 7.

ConocoPhillips Alaska spokeswoman Rebecca Boys said by email that the company does not comment on pending litigation.