Crews work on the Trans Mountain Pipeline expansion project in this undated file photo.

The Federal Court of Appeal is set to release its decision Tuesday on the latest challenge of the Trans Mountain pipeline expansion.

Four First Nations from British Columbia filed court challenges after the federal government approved the project a second time last June.

Tuesday’s appeal decision is expected to come down at 11 a.m. MT.

It specifically focused on government consultation efforts with First Nations groups that took place between August 2018 and June 2019.

The Tsleil-Waututh Nation, Squamish Nation, Coldwater Indian Band and a small coalition of First Nations bear Fraser Valley all argue that the federal government went into these consultations with "pre-determined" outcomes.

The federal government disagrees and says the talks were in fact meaningful, citing that instead of just listening and recording concerns it heard, it instead incorporated them into broader programs to protect the environment. 

The Trans Mountain expansion would carry diluted bitumen from Alberta’s oil sands to the shopping terminal on Metro Vancouver’s coast — nearly one million barrels each day that would triple the existing pipeline’s capacity.

Justin Trudeau’s government purchased the pipeline and related infrastructure for $4.5 billion in 2018. The Prime Minister says the project is needed to reduce price pressures on Alberta oil producers.

Construction on key segments of the expansion is already underway.

The highly contested project has already gone through several significant hurdles, including a years-long federal review by the National Energy Board (NEB) and the Canadaian Environmental Assessment Agency (CEAA).

The Federal cabinet has also approved the project on two different occasions. 

Many of the appeals, including Tuesday's, are based in consultation concerns. Ottawa notes that it has now met with more than 117 communities along the project’s route to mitigate the environmental impact.

When the government issued its second approval of the project, six of the National Energy Board’s 156 recommended conditions were amended to address Indigenous concerns.

The latest Federal Court of Appeal decision comes on the heels of last month’s British Columbia Supreme Court challenge. The province’s top court attempted to regulate what can flow through the expanded pipeline from Alberta, but the case was rejected.

Premier John Horgan said Wednesday that he accepts the court ruling even though he is "not enamoured" with the prospect of a seven-fold increase in tanker traffic in the Strait of Juan de Fuca and Salish Sea.

With files from The Canadian Press