Canada’s government-owned C$31 billion ($23 billion) oil pipeline to the Pacific Coast is facing a new construction challenge just a few months before its scheduled opening.

Trans Mountain is facing a “very challenging” task of drilling through hard rock in the Fraser Valley in British Columbia as it builds a pipeline to almost triple oil shipments from Alberta. The company has proposed a contingency plan to use a 30-inch pipeline instead of the planned 48-inch conduit should the difficulties persist into next month, according to a letter filed with the Canada Energy Regulator.

The project that has faced years of delays and a quadrupling of costs is scheduled to start operation by the end of the first quarter of 2024. In September, the company won regulatory approval to alter a section of the route because of similar drilling challenges.

That alteration was opposed by a local indigenous community called the Stk’emlúpsemc te Secwépemc Nation, which said the change posed a threat to culturally significant land. In an explanation made public Friday, the regulator said failing to alter the route would have caused a 10-month delay and result in a $2 billion loss of revenue for the company.

Trans Mountain has developed contingency plans to mitigate construction challenges in areas along the pipeline corridor, including the current drilling issue, the company said in an emailed statement. The project is more than 95% complete. Filling the pipeline will require about 4.5 million barrels of oil and take six to seven weeks to complete.

Prime Minister Justin Trudeau’s government bought the project from Kinder Morgan Inc. in 2018 after the company threatened to pull the plug amid fierce opposition in British Columbia.

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