VANCOUVER -- Three First Nations are taking the federal government to court over its decision to approve the expansion of the Trans Mountain pipeline that they say poses a serious threat to the environment and their way of life.

Representatives from the Squamish and Tsleil-Waututh nations, and the Coldwater Indian Band say the Crown failed to consult them before approving the project, which would run from Alberta to British Columbia's south coast.

Coldwater Chief Lee Spahan says the pipeline's proposed route poses an enormous risk to his community because of its proximity to their only source of drinking water.

Squamish Chief Ian Campbell says the federal government's talk of entering an era of reconciliation is mere lip service when it comes to the Trans Mountain pipeline expansion.

Prime Minister Justin Trudeau approved the $6.8-billion project last November with 157 conditions, saying he expected the decision to be "bitterly disputed" but ultimately in Canada's best interest.

The proposal, which received backing from the B.C. government last week, would triple capacity along an existing pipeline corridor, and result in a seven-fold spike in tanker traffic from its terminus in Burnaby.