Opponents of the Keystone XL oil pipeline from Canada say the Trump administration is understating the potential for the line to break and spill into water bodies such as Montana’s Missouri River.
U.S. State Department officials held the only public meeting on a new environmental review of the long-stalled pipeline on Tuesday in Billings.
Backers say the $8 billion project would create thousands of construction jobs and boost local tax revenues.
A federal judge blocked it last year, saying more environmental study was needed.
President Donald Trump issued a presidential permit for the line in March in a bid to avoid another unfavorable court ruling.
Montana state Sen. Frank Smith says the 1,200-mile line will break eventually. The Democrat worries that could foul downstream water supplies including on the Fort Peck Indian Reservation.