A B.C. First Nation is asking the Canada Energy Regulator to release its reasons as soon as possible for allowing a modification of the Trans Mountain pipeline's route.

In a letter to the regulator dated Wednesday, a lawyer representing the Stk’emlúpsemc te Secwépemc Nation (SSN) said the decision to grant the route deviation Monday without providing its reasons has left the First Nation without the ability to decide its next steps.

The letter said the First Nation has the right to request a reconsideration of the decision, or to appeal it through the Federal Court of Appeal.

"This has, in fact, created significant uncertainty for SSN and left SSN without the procedural options that would otherwise be afforded to it with the potential for irreparable harm to its rights and title as a result," the letter states.

The Canada Energy Regulator ruled Monday to allow Trans Mountain Corp. to alter the route slightly for a 1.3-kilometre stretch of pipeline in the Jacko Lake area near Kamloops, B.C.

It said it would release its reasons for the decision in the coming weeks.

Trans Mountain Corp, a Crown corporation, had requested the change because of what it said were engineering difficulties in the area related to the construction of a tunnel.

The company had warned that being forced to stick to its original route and construction method could result in up to a nine-month delay in the pipeline's completion, as well as an additional $86 million more in project costs.

Trans Mountain had been hoping to have the pipeline completed by early 2024.

But the Stk’emlúpsemc te Secwépemc Nation, whose traditional territory the pipeline crosses and who had only agreed to the originally proposed route, opposed Trans Mountain's application.

The First Nation has said the new route threatens to disturb land that has spiritual and cultural significance.

The First Nation's lawyer said in the letter Wednesday that Trans Mountain has indicated it wants to break ground on the new route on Oct. 2.

The Trans Mountain pipeline is Canada's only pipeline system transporting oil from Alberta to the West Coast. The expansion, which is currently underway, will boost the pipeline's capacity to 890,000 barrels per day (bpd) from 300,000 bpd.

The pipeline — which was bought by the federal government for $4.5 billion in 2018 after previous owner Kinder Morgan Canada Inc. threatened to scrap the expansion project in the face of environmentalist opposition and regulatory hurdles — has already been plagued by construction-related challenges and delays.

Its projected price tag has also soared: first to $12.6 billion, then to $21.4 billion and most recently to $30.9 billion.

This report by The Canadian Press was first published Sept. 28, 2023.