(Bloomberg) -- Environmentalists and indigenous groups still reeling from the Biden administration’s approval of ConocoPhillips’s 600-million-barrel oil project in Alaska are now taking their fight against the development to federal court. 

In separate lawsuits, the groups are challenging the federal government’s authorization of the Willow development, saying regulators failed to consider smaller, greener options that would better protect the climate and caribou in the region. The filings represent the opening volley in what’s expected to be a protracted legal battle against one of the largest oil-and-gas projects ever permitted on US federal land. 

“We’re asking the court to halt this illegal project and ensure the public knows its true climate impacts,” Christy Goldfuss, chief policy impact officer for the Natural Resources Defense Council, said in a news release. “Permitting Willow to go forward is green-lighting a carbon bomb” that “would set back the climate fight and embolden an industry hell-bent on destroying the planet.”

With construction of the $8 billion project already underway, opponents hope to replicate the legal success they had in 2021, when federal judges issued an emergency order blocking ConocoPhillips Alaska Inc. from opening a gravel mine at the site and later tossed out the Trump administration’s authorization altogether. 

But ConocoPhillips expressed confidence in the new government review that led to the project’s latest approval, announced Monday. 

“The Willow project’s development began in 2017 and has followed a nearly five-year-long regulatory process overseen by the Bureau of Land Management,” said ConocoPhillips spokesman Dennis Nuss. “We believe the BLM and cooperating agencies have conducted a thorough process that satisfies all legal requirements.”

Read More: ConocoPhillips Starts Alaska Work Hours After Biden Announcement

And Senator Dan Sullivan, a Republican from Alaska who has championed the venture, called the lawsuits an expected but “frivolous” development, casting the challenges as the work of “lower-48 elite eco-colonialists” who “are trying to shut down Alaska and silence Alaska Native voices.”

One of the lawsuits was filed by Trustees for Alaska on behalf of the Sovereign Inupiat for a Living Arctic, Alaska Wilderness League, Northern Alaska Environmental Center and three other groups. Earthjustice filed a second lawsuit against the project with the same Alaska-based federal district court on behalf of the Center for Biological Diversity, Defenders of Wildlife and other organizations. 

Opponents could ask the court for an emergency order halting work while the cases proceed.

“The first thing Conoco wants to do is blast a gravel mine in an area that is important for fishing, berry picking and caribou,” said Erik Grafe, deputy managing attorney in Earthjustice’s Alaska regional office. “If the government continues to green-light on the ground activity, it will harm our partners and clients, whose members rely on and cherish this area, and we would consider asking the court to stop it.”

Read More: Biden Backs $8 Billion Oil Project, Imperiling Green Agenda

The lawsuits accuse the Biden administration of violating the National Environmental Policy Act, Endangered Species Act and other laws, arguing the Interior Department failed to analyze the project’s full impacts on climate change, especially in the Arctic region that is warming at four times the rate of the rest of the planet. Over 30 years, Willow could yield some 240 million tons of carbon dioxide emissions, according to the government’s calculations.

The environmental groups also argue the government didn’t fulfill its obligation to consider reasonable project designs that would shrink impacts on caribou and Alaska Native communities that depend on them for subsistence. The opponents also take aim at the Fish and Wildlife Service’s determination that Willow won’t harm polar bears that have dens in the National Petroleum Reserve-Alaska, arguing in one filing that industrial oil operations “pose a multi-faceted threat” to the animals.

Earthjustice also argues the Interior Department wrongly concluded it could not deny nor meaningfully limit the project — and therefore did not consider options to curtail its oil production and associated greenhouse gas emissions.  

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