An intent to sue filed by a coalition of environmentalist organisations, including Earthjustice and the Center for Biological Diversity, is challenging the US Bureau of Land Management's September decision to allow Enefit American Oil (EAO), a subsidiary of Eesti Energia, to build transmission lines and pipelines along a 31-km corridor on federal land.

Filing the intent to sue is the first step required by law towards actually suing the company, AP reported. The Bureau of Land Management now has two months to respond.

The project "would drain billions of gallons of water from the Green River, threaten endangered species and generate enormous amounts of greenhouse gas pollution," the environmentalists said in a news release.

CEO of Enefit American Oil, Ryan Clerico, told AP in an email that production is years away and will require additional government approvals. The company has cooperated with officials during the environmental review process, Mr Clerico said.

The approved plan is the "best environmental option," Mr Clerico said.

The company has invested US$60 million to date in the Utah project, which would produce an estimated 50,000 barrels a day once the site is fully built out, Mr Clerico said. It took six years to get the first governmental approval.

Eesti Energia acquired oil shale reserves estimated at 6.6 billion tons in the state of Utah in March 2011 with a view to developing a shale oil plant with a daily output of 50,000 barrels there.

The process of assessing the project's environmental impact started nearly six years ago. In May last year, US Interior Secretary Ryan Zinke signed the environmental impact assessment report for the corridor, after which it was published.

The record approving the final environmental impact statement authorising a right-of-way-grant, which would allow Enefit American Oil to extend utilities and build an access road on federal land was signed by Joe Balash, the US Interior Department's assistant secretary for lands and minerals management, on 24 September last year.

While Enefit American Oil's energy project would be developed on its own private property, the industrial-scale utility lines needed to serve it would have to either cross federal land, or supplies would need to be transported to the site on a regular basis.

In the case of electricity, the inability to connect to a nearby power line would likely require the company to build a power station. The Bureau of Land Management's analysis found that these alternatives would be more environmentally damaging than allowing a narrow, roughly 23-km utility corridor across federal land. The utility corridor would include water and natural gas supply lines, 138-kV electricity lines, road improvements, and an oil product pipeline, the company said in September 2018.